NAM2012 - Full poster detailsFirst | Previous | Next | Last | All A General Search for Rare Objects in the UKIDSS LAS Author: Nathalie Skrzypek Co-Authors: S.J.Warren (Imperial College London); D.Mortlock (Imperial College London) Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: The YJHK near-infrared bands of the UKIDSS Large Area Survey (LAS) are ideal for finding rare classes of object including high-redshift quasars, cool brown dwarfs, and cool white dwarfs. Here we present the results of a more general search for rare objects, by identifying sources with unusual colours from throughout the YJHK colour space. Unusual stellar sources are identified through chi^2 comparison against a wide set of colour templates, including stars, brown dwarfs, white dwarfs and quasars. Objects that do not match any of the templates are flagged as interesting. A small number of unusual sources merit further investigation. Clustering analysis of high-redshift Luminous Red Galaxies in Stripe 82 Author: Nikolaos Nikoloudakis Co-Authors: T. Shanks (University of Durham); U. Sawangwit (University of Durham) Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: We have measured the clustering for ~130000 colour selected Luminous Red Galaxies via the angular correlation function in Stripe 82 exploiting SDSS DR7 iz and UKIDSS LAS K photometry. We use the cross-correlation technique of Newman (2008) to establish that the average redshift of the LRGs is z~1. We have established that a sample with ~700deg^-2 has a comparable space density to the z~0.68 SDSS AAOmega LRG sample of Sawangwit et al. (2011) Compared to the AAOmega LRG w(θ) scaled to the depth of the Stripe 82 LRGs, the Stripe 82 w(θ) is higher at all scales. Thus at intermediate scales, the z~1 LRGs are not only more clustered than predicted by the long-lived evolutionary model, they are also more clustered than the comoving model. w(θ) shows a very flat slope at large scales which means that the ΛCDM linear model has become a poorer fit than at lower redshift. We present arguments that this is not caused by systematics. HOD models are fitted with best fit parameters : M_ min =2.2x10^13 M_sun, M_1 = 22x10^13 M_sun, F_sat=3.2%, bias=3.1 The flat slope in w(θ) cannot be explained on the basis of the HOD model. If the w(θ) excess proves reliable, we have made a significant detection of non-Gaussianity in the z~1 LRG distribution with an estimated local non-Gaussianity parameter estimate of f_=90+-20 which is a 4σ detection at a level comparable to the present upper limit from WMAP CMB measurements of f_<60. Galaxy-scale gravitational lenses in large surveys: finding them, and what to do with them Author: Neal Jackson Co-Authors: Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: 30 years after the discovery of the first gravitational lens system, we are at the beginning of the period in which new lens systems can be discovered on industrial scales by wide-field surveys at multiple wavelengths. I describe some surveys for lenses from existing surveys such as NVSS, GB6 and UKIDSS and some efforts to find lenses in other surveys. Large numbers of such lenses can be important for understanding the structure of galaxies at different redshifts. I describe the aims and early results of an e-Merlin Legacy Programme aimed at followup of lenses already discovered. Gravitational Lens Statistics with Herschel-ATLAS Author: Jo Short Co-Authors: Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: Whilst lens identification has traditionally been a rather timely exercise, early data from the Herschel-ATLAS survey demonstrated how efficiently lenses can be identified at submillimeter wavelengths using a simple flux criteria. Five lens candidates were identified in the H-ATLAS Science Demonstration Phase (SDP), however the full data set is expected to yield many more numbering in the hundreds. This has led us to consider how to utilise the statistical properties of the lenses. In this work we take a preliminary look at the different assumptions in analytical models for the redshift and magnification distributions of strong gravitational lenses, which include the cosmological parameters, the mass function and the lens density profile (for which we consider singular isothermal sphere and Navarro-Frenk-White approximations). We demonstrate how the SDP data compares to these models and consider about what could be done with the larger data set. Large-Scale Structure Surveys and Violations of Statistical Isotropy Author: Dr. Yashar Akrami Institute of Theoretical Astrophysics, University of Oslo Co-Authors: H. K. Eriksen (Institute of Theoretical Astrophysics, University of Oslo) Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: The principles of isotropy and homogeneity of the Universe on large scales are two cornerstones of the cosmological concordance model. Despite the fact that these assumptions have so far been in good agreement with most cosmological observations of both cosmic microwave background (CMB) anisotropies and the large scale structure (LSS) of the Universe, subtle hints of the contrary have been claimed by some studies of the CMB and LSS data. Any violation of these cosmological principles may have strong impacts on our current understanding of the Universe, and therefore, it is of crucial importance to verify whether such claims hold against the tide of various high-quality data or they are only the results of systematic errors or statistical flukes. Here, we give an update on a previous analysis of the photometric luminous red galaxies (LRG) provided by the Sloan Digital Sky Survey (SDSS) to constrain the parameters of a quadrupolar anisotropic model of the primordial power spectrum. Our analysis is based on the construction of a quadratic estimator of the anisotropy coefficients and we use the latest SDSS-III photometric data (Data Release 8). We also present a more sophisticated technique based on a Gibbs sampling algorithm that can give a more flexible, accurate and computationally efficient way of searching for signatures of violations of statistical isotropy in the LSS data. We show that this method can provide a significantly more powerful tool for the statistical analysis of cosmological data from existing and forthcoming ground-based and space galaxy surveys. Measuring the Cosmic Star Formation Rate Using Deep, Wide-Area, Narrow-Band Imaging Author: Alyssa Drake Astrophysics Research Institute, LJMU Co-Authors: C.Simpson, I.K.Baldry, C.A.Collins, P.A.James (Astrophysics Research Institute, Liverpool John Moores University) Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: The advent of wide-field narrow-band surveys allows for the first time the analysis of large statistical samples of star-forming galaxies, reaching lower stellar masses and star formation rates (SFRs) than ever before. Using ultra deep data from the SXDF-UDS Field, we construct a sample of >7000 narrowband-selected emission-line galaxies, in 12 redshift slices ranging from z=0.14 out to z=1.46. We use broad-band photometry across 11 filters from CFHT u band through to Spitzer IRAC, to determine accurate photometric redshifts, and confirm their reliability using ~250 spectra from the Magellan Telescopes. We trace the evolution of the SFR as a function of stellar mass to <108 Msun (and SFRs <<1 Msun yr-1) across ~10 Gyr. The WIRCam Deep Survey Author: Rich Bielby Co-Authors: O. Ilbert (LAM), P. Hudelot (IAP), H. J. McCracken (IAP), E. Daddi (CEA Saclay), J. P. Kneib (LAM), Y. Mellier (IAP), C. Willott (NRC-CNRC) Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: We present a new near-infrared imaging survey in the four CFHTLS deep fields: the WIRCam Deep Survey (WIRDS). WIRDS comprises extremely deep, high quality J, H and Ks imaging covering a total effective area of 2.1 sq. deg. and reaching AB 50% completeness limits of ~ 24.5. We combine our images with the CFHTLS to create a unique set of eight-band ugrizJHK photometric catalogues in the four CFHTLS deep fields; these four separate fields allow us to make a robust estimate of the effect of cosmic variance for all our measurements. We use these catalogues in combination with 9,800 spectroscopic redshifts to estimate precise photometric redshifts, galaxy types, star-formation rates and stellar masses for a unique sample of 1.8 million galaxies. We present an overview of the latest results based on the WIRDS data in the CFHTLS fields, including the evolution of the galaxy stellar mass function and mass-selected galaxy clustering to z~2, the identification of high redshift (z>1) clusters and the luminosity function of z=6 LBGs. Ultra-strong UV FeII Emission in a Large Quasar Group Author: Kathryn Harris Co-Authors: R.G.Clowes(University of Central Lancashire); L.Haberzettl (University of Louisville); S.Mitchell(University of Louisville); M.J.Graham (California Institute of Technology); L.E.Campusano (Observatorio Astronomico Cerro Calan, Chile); G.M.Williger(Lab. Fizeau, University de Nice);I.K.Sochting (University of Oxford) Session: COS1: Cosmology and Structure Evolution with Wide-Field Optical and NIR Imaging Surveys Displayed during: Poster Session B Summary: I would like to present a region containing an excess of strong and Ultra-strong UV FeII emitting quasars, twice the number of previously published similar objects. These 16 quasars are spread over a redshift range 1.1 Improving the Spectroscopic Atomic Line Database Author: Dr Matthew Ruffoni Co-Authors: Dr J.C.Pickering (Imperial College London) Session: COS2: Future wide-field massive spectroscopic surveys with 4m-telescopes Displayed during: Poster Session B Summary: High-resolution, high-quality spectra from both ground- and space-based spectrographs are vital in many fields of astronomy. However, they also highlight the inadequacies of the existing atomic database. Such inadequacies will be further exposed by future spectrographs, such as those on Gaia and E-ELT.
For Gaia, follow-up measurements with a ground-based MOS on a 4-m class telescope will be crucial in extracting the most from the satellite's spectra. Yet neither the substantial investment in Gaia, nor the resources expended on such a follow-up, will be fully exploited so long as spectral analyses are limited by the quality of the atomic database. An investment must, therefore, also be made in improving the accuracy and reliability of parameters associated with important atomic lines.
In many cases, order of magnitude improvements are needed and are achievable using Fourier transform spectroscopy, where wavelengths are accurate to at least 1:10^7 (30 ms^–1, 0.15 mÅ at 1500 Å), and f-values to a few percent. We present an overview of current needs for accurate atomic data, particularly f-values for iron group element spectra in the IR, optical, UV, and VUV spectral regions. Examples of current work for SDSS-III/APOGEE will be shown, which could be extended to support Gaia. Mass Calibration of the South Pole Telescope Galaxy Clusters Author: Bazin Ludwig Maximilian Universitaet Muenchen Co-Authors: Bazin (Ludwig Maximilian Universitaet Muenchen) Session: COS2: Future wide-field massive spectroscopic surveys with 4m-telescopes Displayed during: Poster Session B Summary: The South Pole Telescope, a 10-m telescope observing the CMB in 3 mm-wave bands, is a great machine to detect galaxy clusters using the Sunyaev Zeldovich Effect. The SPT cluster survey is now finished and it covers 2,500 sqdeg of the south hemisphere sky. I will present the SPT galaxy cluster sample and followups in optical, NIR and X-ray. I will summarize the cosmological analyses, and mainly focus on the SZ mass-observable calibration efforts that the collaboration is pursuing. In particular, I will present our calibration method based on dynamical masses using spectroscopic follow-up, a comparison with X-ray mass calibration, and limitations. WEAVE - a new wide-field multi-object spectrograph for the William Herschel Telescope Author: Chris Benn Co-Authors: M. Balcells (ING), D. Abrams (ING), G. Dalton (Oxford/RAL), S. Trager (Groningen), D. Carter (LJMU), C. Evans (ATC, Edinburgh) Session: COS2: Future wide-field massive spectroscopic surveys with 4m-telescopes Displayed during: Poster Session B Summary: WEAVE is a new multi object spectrograph (1000 fibres 2-deg field) planned for the
4.2-m William Herschel Telescope on La Palma. First light is expected in 2017.
Are z~5 QSOs found in the most massive high redshift halos? Author: Kate Husband Co-Authors: M. Bremer (University of Bristol, UK), L. Douglas (University of Bristol, UK), L. Davis (University of Bristol, UK), E. Stanway (University of Warwick, UK) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: Luminous high redshift quasars are thought to exist within the most
massive dark matter halos (M > 10^13 Msun) in the young universe, where
simulations suggest the strongest evolution is expected to have
occurred in the relatively brief time since the Big Bang. Given the expected halo clustering behaviour, the quasars may trace volumes
containing an overdensity of other high redshift galaxies (i.e. Lyman
Break Galaxies, LBGs). To test this hypothesis we searched three ~3'
(~1Mpc at z~5) z=5 quasar fields for strongly star forming LBGs at the
quasar redshift. We compared the numbers of spectroscopically-confirmed LBGs in these fields to those found through an identical procedure in blank sky fields (ESO Remote Galaxy Survey, ERGS; Douglas et al.'09,'10). We find no evidence for
significant overdensities in the quasar fields; they appear typical of
those found in ERGS. The lack of LBG clustering around high redshift
quasars suggests that either high redshift quasars do not trace the
peaks in the mass density at high redshift, or if they do, that LBGs
are poor tracers of galaxy evolution in such high-redshift
environments. Either way, this indicates our understanding of early
galaxy formation is incorrect.
EAGLE: Producing Realistic SPH Simulation Data Author: Michelle Furlong Institute for Computational Cosmology, Durham University Co-Authors: R. G. Bower(Institue for Computational Cosmology), T. Theuns(Institute for Computational Cosmolgy), Y. Rosas-Guevara(Institue for Computational Cosmology), J. Schaye(Leiden University), R. A. Crain(Leiden University), C.M.Booth(Kavli Institute for Cosmological Physics), C. Dalla Vecchia (Max Planck Institut fur Extraterrestrische Physik) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: Understanding the combination of ingredients required in galaxy formation, to produce the observed galaxy population, remains one of the challenges of Cosmology. Although the background cosmology is well understood, the properties of galaxies depend sensitively on the star formation model, stellar feedback, the effects of metallicity and the formation of black holes and their associated feedback. Using sub-grid physics for these processes introduces further parameters to simulations, which then need to be constrained by observations. A key aspect of the Eagle project is to reproduce the observed stellar mass function, through tuning the sub-grid parameters, focusing on the Type II SN feedback and AGN feedback. The completed data will consist of a 100Mpc^3 N-body SPH simulation with gas particle resolution of ~10^6 solar masses, providing sufficient resolution to study Milky Way size galaxies, with 10^5 particles. This size of simulation at such a high resolution puts Eagle as one of the largest SPH simulations to be carried out, with an added challenge of reproducing observable data. While the full volume is still in the preparatory stages, results for smaller volumes and zoomed simulations, constraining parameters are currently available. These tests also outline how the parameter selection can be carried out. Halo Statistics and Substructure at High Redshift Author: William Watson Co-Authors: I. T. Iliev (University of Sussex) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: Using a suite of large N-Body Dark Matter Simulations (with 28bn - 216bn particles) the halo mass function is probed at high redshifts (z > 6) and compared to existing analytic functions from the literature. Two spherical overdensity (SO) halo finders and one Friends-Of-Friends (FOF) halo finder were used in the analysis. In addition, a presentation of the substructure of the most massive halos from the simulations is given, found using the AMIGA Halo Finder (AHF) and SUBFIND. Non-Gaussianity in Large Scale Structure and Minkowski Functionals Author: Geraint Pratten Co-Authors: D. Munshi (Cardiff University) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: Minkowski Functionals (MFs) are topological statistics that have become one of many standard tools used in investigating statistical properties of cosmological random fields.To lowest order, the MFs depend on three generalised skewness parameters that can be shown to probe the bispectrum with differing weights. Recent studies have advocated the use of a power spectrum associated with the bispectrum, called the skew-spectrum, that has more power to distinguish between various contributions to the bispectrum than the conventional formalism adopted when using the Minkowski Functionals. In this talk we will review the motivations for studying non-Gaussianity and emphasise the importance of the momentum dependence of higher order correlators in investigating inflationary models before introducing the skew-spectra, applied to galaxy surveys, as a tool for investigating primordial and gravitationally induced non-Gaussianity. Numerical simulations with GPUs Author: Martin Zintl Co-Authors: A.M. Burkert (University Observatory Munich) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: Many astrophysical problems are limited by the computational power of the machines running those simulations. Therefore, additional hardware to assist the CPU of a computer have been used in the past (Grape boards, FPGAs), to speed up simulations. Graphics processing units (GPUs) provide a novel way to gain massive performance speedups in certain situations due to their highly parallel nature.
We will talk about the opportunities, but also the challenges of running simulations on a GPU. Since the raw floating point performance of a GPU exceeds the performance of a CPU by far, there is the potential for significant speedups. Early tests show that our SPH simulation code on one consumer GPU is approximately 60 times faster than the standard cosmological code "Gadget-3" running on a Core i7 Quadcore processor.
We will also present a few results of simulations run with this code: The collision of two cold gas clouds with high mach numbers in an isothermal three-dimensional simulation, and the problems of standard SPH regarding the growth rate of the Kelvin-Helmholtz-instability in two dimensions, with and without various SPH modifications. Particle-by-Particle M2M Galaxy Simulations Author: Jason Hunt Co-Authors: Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: The next European Space Agency (ESA)’s cornerstone mission, Gaia, is expected to be launched in 2013. We are developing a made-to-measure (M2M) Galaxy model to reconstruct the mass distribution and stellar kinematics of each component of the Milky Way, such as the thin and thick discs, bar/bulge and halo, from the data from Gaia and related surveys. M2M was originally suggested by Syer & Tremaine (1996), which adapts an existing model to better fit ‘observables’ by altering the particle weights of an N-body model. As the Gaia data will be in the form of individual stars, we have newly developed a particle-to-particle M2M (ppM2M), where the target observables are compared with the model observables at the position of target particles, i.e. stars. We demonstrate that ppM2M is capable of reproducing the target N-body models, including Hernquist (1990) models and disc galaxies simulated with N-body code.
The Influence of Gas Physics on SZ Pressure Profiles Author: Simon Pike Co-Authors: Scot Kay - University of Manchester Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: The Sunyaev-Zel'dovich or SZ effect is caused by CMB photons being scattered off free electrons via Compton scattering, creating a predictable distortion in the CMB. The intracluster medium or ICM is a heated plasma in approximately hydrostatic equilibrium at the centre of clusters that forms the major contribution to the SZ effect. The SZ effect can be used to investigate the scaling relation between the Y parameter, which is a volume integral over the pressure of the gas, and cluster mass. It is therefore important to investigate how gas physics within the cluster might affect the pressure profile, and therefore its Y parameter. In my poster I will show preliminary results of a new set of 30 hydrodynamical simulations, spanning a mass range of 1e14 to 1e15 M_sun/h. These simulations will be used to see how the gas physics, including cooling, star formation and feedback will effect the pressure profiles and the SZ Y parameter.
The predicted UV colours of galaxies at z>3 Author: Violeta Gonzalez-Perez Co-Authors: C. Lacey (Durham), C. Baugh (Durham), S. Wilkins (Oxford), C. Frenk (Durham), T. Theuns (Durham) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: The rest frame ultra-violet (UV) colours of galaxies are a powerful tool to select galaxies at z>3, in fact, the new Hubble Space Telescope has recently revealed several candidates at z=10. The UV continuum slope is widely used to estimate the dust content of galaxies and it can give us information about the end of the reionisation epoch. In this talk I will present a theoretical study of the UV colours of galaxies at z>3. Using GALFORM, a semi-analytical model of galaxy evolution, I will present results on how UV colour change with changing quantities from the physical distribution of dust with respect to stars to the dust extinction curve adopted, and how these affect the knowledge that we can extract from analysing the UV continuum slope. The role of the AGN in the evolution of Eagle galaxy groups. Author: Yetli Rosas-Guevara Co-Authors: R.G. Bower( ICC Durham University), C. Booth(University of Chicago ), J. Schaye (Leiden Observatory Leiden University ), Adrian Jenkins(ICC Durham University), R.Crain (Leiden Observatory Leiden University ), T.Theuns (ICC Durham University and University of Antwerp ), C.S. Frenk(ICC Durham University) , M. Furlong (ICC Durham University) Session: COS3: Simulations of the formation of galaxies and larger structures Displayed during: Poster Session A Summary: Previous studies have shown that the AGN plays a key role in the shaping of the high end of stellar mass function and in the evolution systems such as groups and clusters. Motivated by this,, we study the evolution of the galaxy groups focusing on the variations in AGNs physics implemented in Evolution and Assembly of Galaxies and their Environments (EAGLE) project. In order to efficiently study the formation of galaxies in high mass haloes, we perform a set of hydrodynamical resimulations of galaxy groups of 10^13-14 h^-1 Msun at a resolution of 10^6 h^-1 Msun per gas particle. We explore some parameters of the AGN prescription. We focus mainly on follow the evolution of the Central Brightest Galaxy (CBG) and its star formation history as well as the Black Hole (BH) Mass -Bulge Mass relation. We explore the impact of several parameters such as the threshold amount of energy released by the BH to its surrounding gas and halo mass at which we inject BH seeds.
Discrimination between cosmological constant, quintessence, and modified gravity Author: Houri Ziaeepour Max Planck Institute fur Extratresstrische Physik (MPE) Co-Authors: Session: COS4: Modelling Dark Energy and Modified Gravity Displayed during: Poster Session B Summary: In what concerns dark energy, the ultimate goal of space and ground based surveys is discriminating between various candidate models and a cosmological constant. Here we report results of a work on finding the best set of parameters and measurables for this purpose. In particular we show that independent measurements of cosmological parameters of homogeneous component - the background cosmology - and anisotropies are necessary, notably for distinguishing between interacting
quintessence models and modified gravity. This put in evidence for the advantage of surveys able to observe Large Scale Structures as well as a large number of supernovae. The role of CMB measurements for improving discrimination will be mentioned too. We also propose quantities that determine the discrimination power of a survey independent of observed proxy. (based on arXive:1112.6025, submitted)
String Quintessence and the Formulation of Advanced Quantum Gravity Author: Andrew Worsley Co-Authors: Session: COS4: Modelling Dark Energy and Modified Gravity Displayed during: Poster Session B Summary: Since the publication of the general theory of relativity (GTR), gravity has been described by classical field equations. However, mathematically GTR results in the formation of infinite density singularities in black holes, it challenges simultaneity and causality, and it is generally incompatible with quantum mechanics. A separate problem is the presence of “dark energy”, the energy inherent in space-time. GTR helps explain this energy by the addition of a separate cosmological constant. However, what is required are formulae which treat the energy in space-time as an integral part of quantum gravity. This space-time energy is treated as integral in the quintessence model, and may be resolvable by the use of a minimum energy scale. In this paper we use the standard minimal energy scale, Planck’s constant, and in turn define a new quintessence. Using this string quintessence, we obtain advanced quantum gravity (AQG), which technically agrees exactly with GTR, in the range where GTR has been widely tested. Additionally, the principle of relativity is also maintained, and advanced in order to restore simultaneity and causality. Moreover, using string quintessence, AQG resolves the difficulties related to singularities, and in turn explains the apparent presence of dark energy. The separate presence of “dark energy” can also be explained. Overall, in this paper gravitation is taken to the next level, black holes and in turn dark matter are explained and “dark energy” the presence of space-time energy, becomes integral to the equations of advanced quantum gravity (AQG). Testing modified gravity in the Solar System using LISA-pathfinder Author: Pasquale Galianni School of Physics & Astronomy, the University of St Andrews Co-Authors: A.Martin Feix (Department of Physics, Technion - Israel Institute of Technology); B.Hongsheng Zhao;B.Keith Horne (SUPA, School of Physics and Astronomy, the University of St Andrews)
Session: COS4: Modelling Dark Energy and Modified Gravity Displayed during: Poster Session B Summary: There are many points in the Solar System where the total gravitational pull exerted by the Sun the planets and the galaxy cancels out exactly. These points, which do not coincide with the Lagrangian points, are embedded into low acceleration regions where paradigms a` la MOND predict significant deviations from Newtonian mechanics.
Two of these bubbles are close enough to Earth to be visited by spacecrafts, providing a unique occasion to test the laws of gravity into extremely low gravitational acceleration regimes.
I will discuss the possibility of testing MOND and QMOND using the instruments on-board the LISA-pathfinder spacecraft, which has been scheduled for launch in 2013.
An SPMHD Mean Field Dynamo Author: Federico Stasyszyn Universitäts-Sternwarte München (USM) Co-Authors: D. Elstner (AIP); Session: CP1: Current Developments in Numerical astrophysics Displayed during: Poster Session A Summary: Following the developments in SPMHD we implemented the turbulent transport terms in the induction equation for the evolution of the magnetic field in , with the aim to perform realistic modelling of dynamo action in global galaxy simulations.
Besides the spatial dependent turbulent diffusion $\eta$ also the $\alpha$-tensor is included.
For a disk setup we could verify our numerical results with a known analytical model of Meinel 1990.
Further comparisons with grid based numerical simulations for disks with a galactic rotation law and an anisotropic $\alpha$-effect are shown.
This allow us to perform global galaxy simulations with a subgrid model for dynamo action, which can be linked to upcoming and present day radio observations Simulations of Cosmological Magnetic Fields using GCMHD+ Author: David Barnes Co-Authors: Session: CP1: Current Developments in Numerical astrophysics Displayed during: Poster Session A Summary: Observations show that a range of galaxy clusters are permeated by cosmological magnetic fields of micro gauss strength. The origin of these fields is uncertain and several processes have been suggested to generate them. Numerical simulations are required to show how the strength and profile of a cosmological magnetic field from a generation mechanism changes in a range of systems. We simulate the formation of ten different galaxy clusters with a range of final virial masses using GCMHD+, where the gas particles are embedded with a homogeneous primordial magnetic field. The merging of protoclusters and infall of material lead to an amplification of the magnetic field in the cluster and the emergence of a radial profile for the magnetic field. We show how the magnetic field and the amplification of the field changes with the mass of the system. The effect of the resolution of the simulation on the strength and profile of the cosmological field is also shown for one system. Updated GCD+: A new Galactic Chemo-Dynamical evolution code Author: Awat Rahimi Co-Authors: D.Kawata (UCL-MSSL) Session: CP1: Current Developments in Numerical astrophysics Displayed during: Poster Session A Summary: We have made several important enhancements to our original Chemo-Dynamical galaxy evolution code: GCD+. GCD+ is a N-body/SPH code which takes into account self-gravity, hydrodynamics, radiative cooling, star formation, SNe feedback and chemical enrichment. The new code incorporates new schemes for gravitational N-body dynamics and SPH. We implement a novel star formation and feedback recipe. We describe these new schemes and outline their effects on numerical simulations of galaxy evolution. The new schemes lead to a significant improvement in the ability of TreeSPH codes, such as GCD+, to capture strong shocks and model Kelvin-Helmholtz instabilities. A Multi-Wavelength View of the ISM in Nearby Galaxies Author: Ioannis Bagetakos Co-Authors: E.Brinks (University of Hertfordshire) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We are developing an objective, automated method to compare multi-wavelength images based on 2–D pixel-by-pixel cross-correlations. We introduced a measure for the degree of correlation, Ccoef, which takes values from 1 (perfect correlation) to −1 (perfect anti-correlation). This we subsequently applied to NGC 2403, in a pilot project. We produce spatially resolved cross-correlation maps, on scales of 250 pc to 1000 pc and radial profiles of the cross-correlation coefficients. We find that 1.) all dust tracers, 8μm–70μm, are well correlated (Ccoef > 0.7) at all scales; 2.) all the star formation tracers are well correlated at scales larger than 500 pc (Ccoef > 0.6); 3.) at 250 pc scale, FUV correlates poorly (Ccoef ~ 0.3) with any the dust tracer, a direct consequence of the absorption of FUV photons by dust; and 4.) neutral atomic hydrogen is tightly correlated with the 8μm emission (Ccoef ~ 0.6), illustrating the fact that HI is mixed with PAH’s. Concurrant star formation and black hole growth in the most massive galaxies Author: Jason Rawlings Co-Authors: N.Seymour (CSIRO Astronomy & Space Science)
M.J.Page (MSSL-UCL)
M.Symeonidis (MSSL-UCL) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: High redshift radio galaxies (HzRGs) are extremely powerful, rare, radio-loud AGN whose hosts are known to be among the most massive galaxies in the Universe. While it is expected that the AGN has a strong contribution to the bolometric output, about a third of HzRGs have sub-mm detections which implies considerable star formation in the host galaxy. While observations at these wavelengths inform us of the cold dust associated with the galactic star forming regions, they reveal little about the AGN buried deep within. At mid-infrared (MIR) wavelengths however, both components can play an important role in terms of the energy output of such objects. In order to disentangle the contributions from AGN activity and star formation, we obtained MIR spectra of a sample of HzRGs (1 < z< 3.2) using the Infrared Spectrograph on-board the Spitzer Space Telescope. About a third of the MIR spectra in our sample show polycyclic aromatic hydrocarbon features indicative of considerable star formation and most show relatively weak silicate absorption, implying a more clumpy and extended dust structure surrounds the central engine. With the aid of a library of AGN and starburst models, we examine the properties of HzRGs such as star formation rates, AGN unobscured luminosities and extinction. Our aim is to gain a better understanding of the connection between star formation and the radio-loud phase of powerful obscured AGN. Deep Radio Continuum Imaging Of The Dwarf Irregular Galaxy IC 10: Tracing Star Formation And Magneti Author: Volker Heesen Co-Authors: U. Rau (NRAO); M. Rupen (NRAO); E. Brinks (U Hertfordshire); D. Hunter (Lowell) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We exploit the vastly increased sensitivity of the Expanded Very Large Array (EVLA) to study the radio continuum and polarisation properties of the post-starburst, dwarf irregular galaxy IC10 at 6 cm, at a linear resolution of ~50 pc. We find close agreement between radio continuum and Halpha emission, from the brightest HII regions to the weaker emission in the disk. A quantitative analysis shows a strictly linear correlation, where the thermal component contributes 50% to the total radio emission, the remainder being due to a non-thermal component with a surprisingly steep radio spectral index of between -0.7 and -1.0 suggesting substantial radiation losses of the cosmic-ray electrons. We confirm and clearly resolve polarised emission at the 10-20% level associated with a non-thermal superbubble, where the ordered magnetic field is possibly enhanced due to the compression of the expanding bubble. A fraction of the cosmic-ray electrons has likely escaped because the measured radio emission is a factor of 3 lower than what is suggested by the Halpha-inferred SFR. Dust heating in nearby galaxies from the Herschel Reference Survey Author: Lingjie Kong Co-Authors: George J. Bendo (University of Manchester), Herschel Reference Survey, Herschel Virgo Cluster Survey Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Recent research with Herschel Space Observatory data has shown that dust emission at >250 microns appears to be heated by the total stellar population rather than just star forming regions. This has implications for using dust to measure star formation and for modelling dust emission. However, these results have been based on observations of a relatively small number of galaxies. We expand this analysis using data for a subset of galaxies observed by the Herschel Reference Survey. We will compare variations in the surface brightness ratios to tracer of total stellar emission and star formation to identify the dust heating sources, and then we will compare our results with prior observational results for other galaxies and prior modelling results. Flux density variations of radio sources in M82 Author: Melanie Gendre Co-Authors: D. Fenech (UCL); R. Beswick (JBCA); T. Muxlow (JBCA) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: M82 is one of the closest (d = 3.2 Mpc) starburst galaxies known, producing a large population of massive, rapidly evolving stars, and an equally large number of supernovae. In the past 30 years, M82 has been subject to frequent radio monitoring at centimetre wavelengths with the VLA and MERLIN.
With detection of over 50 discrete objects, including over 30 SNRs, these regular observation programmes have the advantage of tracking the evolution of supernova remnants as their shells expand, which provide a way to investigate properties of the Inter-Stellar Medium. Regular observation programmes also allow for the monitoring of flux variability in sources such as 41.95+57.5, which has shown a continued decrease in flux density since its first observation in 1965.
We present the results of the 2009-2010 monitoring sessions of the starburst galaxy M82, obtained with MERLIN)at 5-GHz and e-MERLIN at 6-GHz. Combining the 5-GHz MERLIN epochs to form a map with 11.8 uJy/beam noise level, 52 discrete sources, mostly supernova remnants and HII regions, are identified. These include 3 objects which were not detected in the 2002 5-GHz MERLIN monitoring session: supernova 2008iz, the transient source 43.78+59.3, and a new supernova remnant shell.
Flux density variations, both in the long (1981 to 2010), medium (2002 to 2010) and short (2009 to 2010) term, are investigated. We find that flux densities of SNR in M82 stay relatively constant in most of the sample (~90-95%). In addition, aside from SN2008iz and the well-known variable source 41.95+57.5, 4 sources display long term variations over the period 1981-2010, three of which have measured sizes among the most compact in M82. These variations could be explained by changes in the mediums in which the shocks travel. Galaxy-wide outflows in z~1.5-3.5 infrared-luminous galaxies Author: Christoper Harrison Co-Authors: Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Leading models of galaxy evolution predict an active period, peaking around z~2, of supermassive black hole (BH) and stellar growth. These processes are thought to be self-regulating through powerful active galactic nuclei (AGN) driven outflows; however, direct observational evidence of this at high redshift remains very limited. I present integral field spectroscopy observations, covering the [OIII] emission line, of eight submillimetre-luminous galaxies (SMGs) that host radio-quiet AGN activity. These SMGs display extremely broad (FWHM~1000-2000 km/s) [OIII] emission across 4-15 kpc, a signature of vigorous outflows over galaxy-wide scales. These outflows are dumping considerable amounts of energy into their host galaxies which is likely to disrupt star formation. For example, we identify a spectacular, two-sided, high velocity (v~830 km/s) AGN-driven outflow in a galaxy that is also undergoing a merger and intense star formation activity. We speculate that we are observing galaxies in a transition phase from obscured star formation and AGN activity to an unobscured quasar, potentially a key evolutionary stage in the formation of local massive galaxies. H-ATLAS/GAMA: The star formation history of H-ATLAS galaxies and its correlation to the environmen Author: Ali Dariush Co-Authors: S. Eales (Cardiff University); S. Dib (Imperial College London) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: The aim of this work is to see how star-formation-histories (SFH) correlate with the environmental density and/or dust properties of low-redshift galaxies detected by H-ATLAS. We use multi-band photometric data (e.g. UV, optical, and NIR) in order to measure the SFH of galaxies from their spectral energy distributions (SEDs). To do so, we will consider all galaxies with submillimetre detections and measure their SFHs against a control sample. We analyse differences between the SFHs as well as dust mass/temperature of low-mass and high-mass systems and investigate the effect of environment (density) on such properties. H-ATLAS: The FIR Properties of BAL Quasars Author: Jose Manuel Cao Orjales Co-Authors: J. A. Stevens (University of Hertfordshire); M. J. Jarvis (University of Hertfordshire, University of the Western Cape); D. J. B. Smith (University of Hertfordshire); M.J. Hardcastle (University of Hertfordshire); R. Auld (Cardiff University); M. Baes (Universiteit Gent); A. Cava (Universidad Complutense de Madrid); D. L. Clements (Imperial College London); K. Coppin (McGill University); A. Dariush (Imperial College London); L. Dunne (University of Nottingham); S. Dye (University of Nottingham); S. Eales (Cardiff University); C. Hoyos (University of Nottingham); E. Ibar (UKATC); R. J. Ivison (UKATC and University of Edinburgh); R. Hopwood (Imperial College London); S. J. Maddox (University of Nottingham); M. J. Page (MSSL, University College London); E. Valiante (Universiteit Gent) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We have used data from the Herschel-ATLAS at 250, 350 and 500 microns to determine the far-infrared (FIR) properties of Broad Absorption Line Quasars (BAL QSOs). Our sample contains 49 high-ionization BAL QSOs (HiBALs) and 1 low-ionization BAL QSO (LoBAL) which are compared against a matched sample of 329 non-BAL QSOs. We calculate star-formation rates (SFR) for our individually detected HiBAL QSOs and solitary LoBAL QSO as well as average SFRs for the BAL and non-BAL QSO samples based on stacking the Herschel data. We find no difference between the HiBAL and non-BAL QSO samples in the FIR, even when separated based on differing BAL QSO classifications. Despite tentative claims in the literature, we are unable to show a decisive dependence of CIV equivalent width on FIR emission, suggesting that the strength of any outflow in these objects is not linked to their FIR output. These results suggest strongly that BAL QSOs (more specifically HiBALs) can be accommodated within a simple AGN unified scheme in which our line-of-sight to the nucleus intersects outflowing material. Our results do not support evolutionary models. Herschel Author: Chris Fuller Co-Authors: Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Using the superb resolution and sensitivity of Herschel we have measured
the FIR (100, 160, 250, 350, 500u) fluxes of an optically selected sample
of Coma cluster galaxies. Using these data we fit spectral energy
distributions to derive dust temperature and masses. We cover both the
cluster core which is dominated by early type galaxies and also the
extended outer regions of the cluster. We make comparisons of the FIR
properties of these galaxies with those of a similar sample detected and
measured in the Virgo cluster. Probing the star formation and AGN connection using NMF analysis of IRS spectra Author: Peter Hurley Co-Authors: Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Understanding the star formation and AGN connection in infrared galaxies still poses an interesting problem for astronomers. The infrared spectra obtained from the Spitzer IRS spectrograph, has provided a unique probe, but difficulties remain in utilising the spectra due to the limited modelling tools available for the mid-infrared.
Blind source separation techniques such as principal component analysis (PCA), provide an alternative tool to modelling. PCA has already successfully decomposed the IRS spectra of local ULIRGs into 5 unique components. However, due to the nature of PCA, the components do not have an obvious physical interpretation.
Non negative matrix factorisation (NMF) is similar to PCA, but constrains both weights and derived templates to be non-negative. This more closely resembles the physics of emission in the mid-infrared and as a result the derived components are more physically intuitive.
We have applied the NMF technique to the IRS spectra of galaxies from the CASSIS database (Lebouteiller et al. 2011). Our derived NMF components/templates can be used to quantify the contributions from different physical environments and are therefore an ideal classification tool for constraining properties such as the star formation and AGN contribution for galaxies with IRS data. Radio to infrared spectra of late-type galaxies with Planck and WMAP data Author: Michael Peel Jodrell Bank Centre for Astrophysics, University of Manchest Co-Authors: M. W. Peel [1], C. Dickinson [1], R. D. Davies [1], D. L. Clements [2], R. J. Beswick [1]
[1] Jodrell Bank Centre for Astrophysics, University of Manchester
[2] Astrophysics group, Imperial College London Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Using the Planck ERCSC, WMAP and other archival measurements, we construct continuum spectra of the nearby late-type galaxies Messier 82, NGC 253 and NGC 4945. We find that their spectra are consistent with steep spectrum synchrotron emission, a substantial amount of free-free emission, and cold thermal dust. The higher levels of free-free emission than previously found bring the star formation rate calculated from it into better agreement with that from non-thermal emission. We place limits on the amount of anomalous microwave emission from the galaxies, finding that it is lower than expectations from our own Galaxy.
(MNRAS Letters, 416, 99, arXiv:1105.6336) Spectral Aging In The Lobes of FR-II Radio Galaxies Author: J Harwood Co-Authors: Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: It has become increasingly apparent in recent times that radio-loud active galaxies play an important role in the evolution of galactic populations. Understanding their dynamics and energetics is therefore vital if we are to build a true picture of galaxies came to be the way they are today. Determining the spectral shape of a population can often give key insights in to the underlying physics of a radio source, specifically, the ability to derive information about age of emission and the rate and which energy is being transferred to the local environment. In principle, since higher-energy electrons lose energy faster by synchrotron radiation, we expect to see steeper, more strongly curved spectra in older regions of plasma. Models describing this curvature (‘spectral ageing’), fitted to narrow-band observations of a radio source at several frequencies have been a standard tool in this field for many years. The poor sampling in frequency space has traditionally meant that determining which of these models (if any) are correct has been hard to achieve; however, the capability of the upgraded EVLA to observe at widely spaced frequencies and broad-bandwidths allows this problem to be overcome. Here I present the latest results in using these capabilities to provide high resolution spectral maps to answer the long standing question of possible spectral ageing in the lobes of FRII radio galaxies. Spectroscopic Followup of Radio-loud AGN Sources in the South Pole Telescope Survey Author: Kate Husband Co-Authors: S. Chapman (Institute of Astronomy, UK), J. Vieira (California Institute of Technology, USA) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: A study of radio loud AGN sources in ~1500 square degrees of the South
Pole Telescope point-source survey has revealed three classes of
sources: radio-loud quasars whose radio to sub-mm SED is a flat power
law, radio-loud quasars whose spectrum turns over due to
self-absorption and sources with an upturning spectrum in the
far-infrared (FIR). The upturning spectrum has an excess 'upturn' flux
of 5-84 mJy at 1.4mm thought to be due to thermal emission from
dust. If the upturn is thermal emission from dust the implied
far-infrared luminosities are huge and the sources are ultraluminous
infrared galaxies (ULIRG: L>10^12). Despite this none of the upturning
sources are detected by Plank or IRAS. Follow-up spectroscopy of a
sub-sample of upturns with VLT-ISAAC indicates that these
ATCA-identified radio sources are typically broad line radio-QSOs at
z=1.0-2.3. Possible scenarios are discussed to explain these
observations. Spying on the neighbour - Mapping the ISM and star formation in Andromeda Author: George Ford Co-Authors: Walter Gear (Cardiff University); Steve Eales (Cardiff University); Matt Smith (Cardiff University) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Here we explore how the star formation rate relates to density of gas in M31, and hence test the Schmidt law on smaller scales than was previously possible. We use two methods of calculating the star formation.
FUV + 24µm emission probes the embedded and unobscured star formation separately. We use a modified version of the prescription found in Leroy et al (2008) combining Galex and MIPs data, corrected for the old stellar population. Total infrared luminosity probes dust heating only and is calculated using recently acquired data from the Herschel Space Observatory.
We compare the two methods, and discuss the limitations of both. We further look at possible means to calibrate one or both maps to reach an agreement.
Gas mass is traced by summing the total HI and H2 (from CO). We calculate gas-to-dust ratios at every pixel (dust mass found from Herschel data) and find a variation with radius. This is used to create a second gas map, using dust as the tracer.
The Schmidt law is tested in several elliptical annuli. It appears the dust tracer gives the most consistent results throughout the galaxy, but gives an index much lower than values previously found.
Star Formation and AGN Activity in Interacting Galaxies: A Near-UV Perspective Author: Caroline Scott Co-Authors: Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Galaxy interactions produce intense star formation episodes, driving the build-up of stellar mass and black holes and alter the morphological mix of the universe. While they are routinely included in galaxy formation models, the evolution of star formation and AGN activity is only now being investigated from a purely observational perspective. SDSS and GALEX data is employed to analyse our close pairs catalogue. UV and optical colours are used to approximate recent star formation in close pair systems as a function of separation, galaxy properties (eg. morphology and luminosity) and local environment, and NUV-derived luminosities provide specific star formation rates. Our large homogeneous dataset allows us to study the interplay between star formation and AGN activity. Using SDSS spectra, we probe the AGN fraction and its evolution as mergers advance. The results provide constraints on our current theoretical infrastructure and provide a picture of how merging affects galaxy evolution from an observational perspective using state-of-the-art spectro-photometric data from current large-scale observational surveys. Submillimetre and X-ray observations of star-forming AGN in the epoch of galaxy formation. Author: Mat Page Co-Authors: Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: The present day black hole / bulge mass correlation tells us that star formation and the growth of black holes by accretion must be intimately linked. In the years prior to Herschel, ground based submillimetre observations combined with X-ray surveys identified a subset of luminous QSOs, those with significant X-ray absorption as embedded in powerful star-forming submillimetre galaxies. I will present evidence that the X-ray absorbers in these objects are highly-ionised winds, and discuss the evolutionary-sequence suggested by these observations. I will move on to describe the results obtained from the Herschel Multi-tiered Extragalactic Survey (HerMES) observations of the Chandra Deep Fields, which pairs the deepest
submillimetre images ever obtained with the deepest X-ray surveys. The Herschel data provide the first sensitive glimpse into the far-infrared and star formation properties of a large part of the AGN population at cosmological distances. With Herschel SPIRE we identify star formation in a much greater fraction of AGN than in pre-Herschel observations. The association of X-ray absorption with star-forming QSO host galaxies is found to extend well below the break in the luminosity function of AGN. We discuss the implications of these findings with respect to the co-evolution of galaxies and the black holes that reside in their centres. Sweeping up the Dust in the Low Redshift Universe by Stacking in the Herschel ATLAS Author: Nathan Bourne Co-Authors: S.J.Maddox (Canterbury, NZ); L.Dunne (Canterbury, NZ); and the H-ATLAS and GAMA teams. Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: The Herschel-ATLAS survey provides the largest ever map of the sub-millimetre
sky. We have used over 100 square degrees of this revolutionary data set,
with multi-wavelength photometry and redshifts from GAMA, to conduct
an unbiased census of the dust mass in optically selected galaxies up
to z=0.35, using stacking techniques to recover emission from sources
well below the noise and confusion limits of H-ATLAS. I will summarise the
results and discuss the relationship between the typical dust and stellar
content of galaxies, and how this depends on optical colour, stellar mass
and redshift. The AGN-Starburst Connection in 1 < z < 4 Quasars Author: Ashley K Hyde Co-Authors: D.L.Clements (Imperial College London), H.Patel (Imperial College London), HerMES Collaboration Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We model optical-to-IR SEDs of 38 SWIRE quasars which have optical spectroscopic redshifts. Our key results are: 1) 35/38 are experiencing starbursts. 2) 26 are detected by the Herschel SPIRE instrument. 25/26 are fit by M82/Arp220 starburst SEDs in the FIR, and integrating these templates reveals their host galaxies are HLIRGs (log(L,8-1000um/L,sun)=13-14) which are experiencing very high star formation rates of >10,000Msun/yr where they harbour non X-ray detected quasars, but <5,000Msun/yr if their AGN is X-ray bright (log(Lx/W)>37), with SFRs potentially overestimated depending on IMF. Thus in the latter group the AGN may be suppressing star formation in the host galaxy, consistent with a quenching paradigm. 3) We estimate black hole masses from the CIV or MgII broad line and we find a range of 8.06 < log(M/M,sun)<9.81. We see a clear trend of decreasing Eddington Ratio with increasing black hole mass but no apparent dependence of starburst events on either, which within a quenching scenario implies successive starbursts throughout the evolution of these quasars. The Distribution of Star Formation in a Representative Sample of 69 Barred Galaxies. Author: Richard Taylor Co-Authors: W.X. Maciejewski (Liverpool John Moores University) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We study the distribution of H-alpha emission in barred spiral galaxies from the H-alpha Galaxy Survey, a survey that is representative of a wide range of galaxy luminosities. Of the 69 galaxies in our sample, about half exhibit emission from the main body of the bar, whilst only 13% show emission from the leading edge of the bar. Emission from the nucleus is present in 75% of galaxies, with extended nuclei preferred by strongly barred galaxies, while in weak bars, extended and compact nuclei are both equally common. Nuclear rings are extremely rare in H-alpha emission (6% of the sample). Our findings challenge the generic picture of gas flow in barred galaxies and of the evolution of barred galaxies. The host galaxies and black-hole:galaxy mass ratios of luminous quasars at z~4 Author: Thomas Targett Co-Authors: J.S. Dunlop (IfA, Edinburgh)
R.J. McLure (IfA, Edinburgh) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We present and analyse the deepest, high-quality Ks-band images ever obtained of luminous quasars at z~4, in an attempt to determine the basic properties of their host galaxies less than 1 Gyr after the first recorded appearance of black holes with Mbh > 10^9 Msol. Via carefully-controlled separation of host-galaxy and nuclear light, we estimate the luminosities and stellar masses of the host galaxies, and set constraints on their half-light radii. The quasar host galaxies have K-band luminosities similar to radio galaxies at comparable redshifts, suggesting that these quasar hosts are also among the most massive galaxies in existence at this epoch. However, the quasar hosts are a factor ~5 smaller than the host galaxies of luminous low-redshift quasars. We estimate the stellar masses of the z~4 host galaxies to lie in the range 2-10x10^11 Msol, and use the CIV emission line to estimate the masses of their black holes. The results imply a black-hole:host-galaxy mass ratio Mbh:Mgal~0.01-0.05. This is an order of magnitude higher than typically seen in the low-redshift Universe, and is consistent with existing evidence for a systematic growth in this mass ratio with increasing redshift, at least for objects selected as powerful AGN. The influence of star formation and nuclear activity on the molecular gas in nearby active galaxies Author: Stefanie Muehle Argelander-Institut fuer Astronomie Co-Authors: C. Henkel (Max-Planck-Institut fuer Radioastronomie)
M. Rodriguez (Instituto de Astrofisica de Andalucia)
T. de Maio (University of Colorado)
S. Aalto (Onsala Space Observatory)
E.R. Seaquist (University of Toronto) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Star formation processes and nuclear activity play a crucial role in the evolution of galaxies, locally as well as at high redshifts. The question whether or not the initial mass function (IMF) is universal is subject to intense debate. A number of recent observations have been interpreted as evidence for a non-standard IMF in a variety of environments. Hydrodynamical simulations suggest that the kinetic temperature of the collapsing molecular gas is a key factor for the shape of the resulting IMF. In active environments like the cores of starburst galaxies or near AGN, the dense molecular gas may be much warmer than the dense cores in the Milky Way disk, but unfortunately, the kinetic temperature of the molecular gas in external galaxies is rarely well constrained. We demonstrate the diagnostic power of a selected set of paraformaldehyde lines, in particular in the ALMA era, as tracers of the kinetic temperature as well as of the gas density in external galaxies using our non-LTE radiative transfer model. The first results of our survey of nearby starburst galaxies and AGN using this new tool support the notion of a significant warm molecular gas phase in at least some of these environments. The LITTLE THINGS Survey Author: Elias Brinks Co-Authors: and the LITTLE THINGS Team Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: We present the LITTLE THINGS project, a multi-wavelength dataset consisting of 41 relatively normal, nearby (<10 Mpc) gas-rich dwarf irregular galaxies. LITTLE stands for Local Irregulars That Trace Luminosity Extremes, and is the low-mass, low-metallicity extension of THINGS, The HI Nearby Galaxy Survey. Our data include GALEX UV images, ground-based UBV and Halpha images, some ground-based JHK images, Spitzer archival mid-IR images, and HI-line maps. The HI maps, obtained with the VLA, go deep (12/6/2 hrs in B/C/D arrays) and are characterised by high spectral resolution (<2.6 km/s) and high angular resolution (typically 6", which is 110 pc at the average distance of our sample). Our datasets trace the stellar populations, gas content and structure, dynamics, and star formation indicators in the galaxies, and are being used to answer questions about star formation in dwarf galaxies. All data have now been made publicly available. We give here an overview of the data and the project's aims.
The search for cool baryons at z~5 Author: Luke Davies Co-Authors: M.N.Bremer (University of Bristol); E.R.Stanway (University of Warwick); M.Birkinshaw (University of Bristol); M.N.Lehnert (Observatoire de Paris, Meudon); A.Omont (Institut dAstrophysique de Paris); E. J.Mannering (University of Bristol) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: Lyman Break Galaxies (LBGs) form a substantial fraction of the known high-z (z~5) galaxy population. While these systems have been extensively studied at rest-frame UV/optical wavelengths (probing the bulk of their stellar mass), little work has been undertaken to explore their cool dust and interstellar gas content. In order to fully understand star-formation activity at high-z and the subsequent evolution of early star-forming galaxies, we must observe their complete baryonic budget. Until recently studies of the dust and molecular gas content of the highest-z galaxies has been limited to massive/rare systems which maybe atypical of the general star-forming population at z~5. To this end we have carried out a pilot study, targeting molecular gas and dust emission from regions which are over-dense in LBGs at z~5. We place constrains on the UV-dark baryonic content of high-z galaxies, indicating that these systems are likely to be small, independent galaxies and not super-starburst regions embedded in a much larger obscured system (for reasonable assumptions of T_dust and `X-factor'). Though this study we have pushed the limits of current instrumentation but discuss how the detection cool material at high-z will become routine with the fully operational ALMA. The star formation history of the Galactic Bulge Author: Albert Zijlstra Co-Authors: K. Gesicki (University of Torun, Poland), B. Rees (University of Machester, UK) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: The star formation history of the Galactic Bulge is an important constraint on its origin - either as a separate entity of the Galaxy or as a pseudo-bulge. We derive the star formation history using HST and VLT observations of compact planetary nebulae. Stellar ages are derived from the mass distribution of the central stars. There is evidence for a range of ages, estimated at 10-8 Gyr, with a significant peak for the youngest ages. We derive an approximate star formation rate of 4 solar masses per yr over these 2 Gyr (for a Bulge mass of 10^10 solar masses), with a peak of 8 solar masses per yr during the last 0.5 Gyr. A possible explanation is that the Bulge formed 8 Gyr ago, from an event which scattered stars and gas into the central regions. The structures of the planetary nebulae indicate that the star formation in the Bulge took place under a strong and well-ordered magnetic field. The X-ray/infrared connection in star-forming galaxies Author: Myrto Symeonidis Co-Authors: the HerMES consortium Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: I will present results from our recent study of the X-ray/infrared correlation, carried out as part of the Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed-time key programme, with data from the field of GOODS-North. Combining X-ray data from the 2Ms Chandra survey and infrared data from Herschel's sub-millimeter bolometer array, SPIRE, we are able to investigate the X-ray/infrared correlation in the high star formation rate (SFR), starburst-mode regime for galaxies at cosmologically significant redshifts. Once obvious AGN are excluded, the X-ray/infrared properties of our sample of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) at X-Ray properties of star-forming BzK galaxies Author: Cyprian Rangel Co-Authors: K. Nandra (Max Planck Institut fur Extraterrestrische Physik); E. S. Laird (Imperial College London); S. J. Warren (Imperial College London) Session: GAL1: 12 billion years of star formation and nuclear activity in galaxies - the submillimetre view Displayed during: Poster Session A Summary: X-Ray background models predict a large population of heavily obscured (Compton thick) AGN at z>1 that to date remains undiscovered. These heavily obscured AGN are too faint to be directly detected in even the deepest x-ray surveys, hence we search for this population using multi-wavelength techniques. We present x-ray stacking of a sample of BzK galaxies binned according to the ratio of their Infrared and dereddened UV star formation rates (SFRs) in Chandra Deep Field South (CDFS) 4Ms and Chandra Deep Field North (CDFN) 2Ms. Galaxies with IR SFR greater than their dereddened UV SFR (IR Excess) are deemed to be strong Compton thick AGN candidates, based upon previous stacking analyses using CDFS 1Ms data, while the remaining BzK galaxies (IR Non-Excess) are thought to be purely star forming. A greater proportion of the BzKs have now been directly x-ray detected in the CDFS 4Ms data, ranging from heavily obscured AGN to faint and unobscured AGN. From stacking we conclude the IR Excess galaxies are a mixture of obscured and unobscured AGN and star forming galaxies. The IR Non-Excess galaxies have an almost identical x-ray emission profile but are less x-ray bright. Automated Measurement of Interacting Galaxies in the Sloan Digital Sky Survey Author: Alex Lockey Co-Authors: Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: We investigated an approach to quantifying the morphological effects of galactic mergers. A main sample of visually- and spectroscopically-identified merging galaxies was selected from SDSS DR4, and a control sample of galaxies corresponding to the main sample was selected by matching morphological classification, mass, luminosity and environmental density. The merging and control sample galaxies were modelled using single-Sèrsic model fits to SDSS r-band images, and the model error used to calculate a disruption value. The disruption value is found to be substantially dependent on morphological type, but to also vary between merging galaxies and control galaxies. The disruption value is shown to vary with the projected separation of interacting galaxies. Building the galactic halo through the evolution and dissolution of star clusters. Author: Poul Alexander Co-Authors: Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: An unknown portion of galactic halo stars originate in globular clusters. The evolution of such clusters therefore represents an ideal means through which we can explore their contribution to the formation and evolution of the halo, and allows us to link the halo's cosmological origins to it’s current stellar kinematics and population. We have developed a computationally fast yet physically motivated code to efficiently explore the long term evolution of star clusters. We find that this code is able to reproduce N-body simulations to ~10% accuracy, over a wide range of initial conditions. Using this code, we are able to rapidly explore an extremely large parameter space expressing the distribution and nature of star cluster formation, and hence place constraints on the nature and origin of the stars that comprise the galactic halo. Diagnostics of Dusty vs Non-Dusty Early-Type Galaxies Author: Nicola Agius University of Central Lancashire Co-Authors: A.E.Sansom (UCLan) Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: Early-type galaxies are known for being generally smooth, passive, red objects with no spiral arms. With the aid of recent results from Herschel-ATLAS and GAMA, a sample of 508 morphologically selected ETGs detected in the sub-mm has been created. By comparing and contrasting this sample with an optically selected sample of ETGs undetected in the sub-mm, we explore their relative properties. We examine the environmental densities of these two samples and find no significant difference in their environments. The dusty ETG data are fit with a modified Planck function, giving us specific dust masses which increase with decreasing stellar mass. Statistical testing shows that other host galaxy properties are also shown to have different distributions for the two samples. On the optical+NIR color gradients in the external regions of early-type galaxies Author: Francesco La Barbera Co-Authors: I. Ferreras (UCL-MSSL); R.R. de Carvalho (INPE-DAS); A. Pasquali (ARI-ZAH); E. Merlin (INAF-OAP) Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: We stack the optical+NIR colour profiles, out to a large
galactocentric distance of eight Re's, for a sample of ~1000 nearby
(z~0.05), massive (M*~10^10-10^11Msun), early-type galaxies (ETGs),
with grizYJHK photometry available from SDSS and UKIDSS-LAS. ETGs are
split according to the environment where they reside, into field and
group galaxies. Combining g-r through g-K colours allows us to
constrain stellar population properties (i.e. age and metallicity)
from the central regions to the outskirts of ETGs. I will present how
age and metallicity profiles depend on stellar mass, environment, and
galactocentric distance, providing new constraints to the formation
and evolution scenario of massive galaxies.
Quantifying the stellar assembly in early-type galaxies using spatially-resolved spectro-photometry Author: Sugata Kaviraj Imperial College London and the University of Oxford Co-Authors: R. W. O'Connell (Virginia); B. C. Whitmore (Space Telescope Science Institute); J. Silk (IAP and Johns Hopkins); M. Cappellari (Oxford); R. M. Crockett (Oxford) Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: Traditionally considered to be old and passively-evolving, I show how recent rest-frame UV studies have demonstrated (and quantified) widespread recent star formation in early-type galaxies (ETGs). Together with the past literature these studies show that, while the bulk of the stellar mass in ETGs is old, ~20% forms after z~1, via minor mergers between ETGs and gas-rich dwarfs. While our traditional understanding of galaxy evolution is largely based on integrated spectro-photometry, I demonstrate how spatially-resolved studies, using high-resolution UV/optical imaging and integral-field spectroscopy (IFS), is a uniquely powerful tool to quantify the formation of individual ETGs. Combining new HST/WFC3 UV-optical imaging and IFS from the SAURON project, I present a case study of the ETG NGC 4150, showing (empirically) that this galaxy experienced a minor merger with mass ratio ~1:20 around ~0.9 Gyr ago, which formed 3% of its stellar mass and a young kinematically-decoupled core. A UV/optical analysis of its globular cluster system then shows that the bulk of the stars in this galaxy formed ~6-8 Gyrs in the past. I introduce a new HST/WFC3 programme (PI: Kaviraj), that will extend this spatially-resolved analysis to a representative sample of ETGs and serve as a prototype for work using the extremely large telescopes, that will routinely provide high-resolution imaging at the end of this decade. Structure and Dynamics of Hot Stellar Systems Author: Mark Norris University of North Carolina at Chapel Hill Co-Authors: Sheila J Kannappan (UNC - Chapel Hill) Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: I will present results from two studies:
(1) Determining the dynamical mass of galaxies like S0s, where cold gas emission is weak or absent, and where neither stellar dispersion or stellar rotational support dominates has traditionally been extremely difficult. In order to produce a more reliable mass estimator for S0s we have therefore examined the relations between central stellar velocity dispersion, and the maximum rotation velocity of both stars and cold gas for more than 60 S0 galaxies drawn from the RESOLVE survey (http://resolve.astro.unc.edu/). In doing so we are determining a dynamical mass estimator for S0s which improves on standard practice.
(2) The second project is an HST archival survey designed to investigate the nature and origins of massive globular clusters, ultra compact dwarfs, and compact elliptical galaxies. We are finding many of these previously understudied objects in a range of environments from the field to galaxies clusters. We find that some massive GCs/UCDs are created in periods of intense in-situ star formation, while others are created during later accretion events. We will discuss how the objects discovered to date put constraints on the two-phase build up of galaxy halos. Testing Theoretical Element Response Functions with an Empirical Stellar Spectral Library. Author: Dr. Anne E. Sansom University of Central Lancashire Co-Authors: Session: GAL2: Diving into the outer halos of elliptical galaxies: clues to galaxy formation and evolution Displayed during: Poster Session A&B Summary: Element abundance ratios hold important clues to understanding
the evolution of stellar populations, through the varying timescales
of different nucleosynthetic contributors(including SNII, SNIa,
stellar winds and mass loss). Newly measured and compiled [Mg/Fe]
ratios in the MILES stellar library are used to confront models
of different star spectra. Such models have been used in recent
years to provide estimates of differential changes in spectral
line strengths of stellar populations, due to enhancements in [alpha/Fe].
This talk presents tests of the most widely used sets of theoretical
element response functions. Using magnesium as a proxy for all alpha
elements the reliability of these theoretical response functions are tested against empirical observations. This study probes the reliability of current
methods of measuring element abundance ratios in stellar populations.
Kinematic analysis of the M31 halo globular clusters Author: Jovan Veljanoski Institute for Astronomy, University of Edinburgh Co-Authors: A.M.N. Ferguson (Institute for Astronomy, University of Edinburgh );
D.A.Mackey (Research School of Astronomy & Astrophysics, Australian National Observatory, Mt. Stromlo Observatory);
M.J.Irwin (Institute of Astronomy, University of Cambridge );
A.P.Huxor (Astronomisches Rechen-Institut, Zentrum fur Astronomie der Universit¨at Heidelberg); Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: The halo of M31 hosts nearly 90 globular clusters. Using low resolution spectra, we present kinematic and chemical analysis for a significant sample of these objects. Many of the M31 outer halo globular clusters lie along stellar streams, suggesting that they have been accreted along with their host dwarf galaxies. We discuss evidence for this via velocity and metallicity correlations of globular clusters which lie along particular debris features. On the star formation history of IKN dSph Author: Tudorica Alexandru Argelander Institute for Astronomy Co-Authors: Iskren Georgiev (Argelander Institute for Astronomy); Ana Chies Santos (Nottingham University) Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: I will present an optical-NIR photometric investigation of the
age and metallicity of globular clusters in the ultra-faint
IKN dwarf spheroidal galaxy in the M81 group. Age and
metallicity distributions of GCs in a galaxy can provide valuable
information about the physical conditions of major starburst
episodes during which these GCs were formed. With the highly sensitive to
age and metallicity VIKs color indices we find a large spread in age
(1-15Gyr) and metallicity (-1.6 Scaling relation of dwarf galaxies in the core of Coma cluster Author: Habib Khosroshahi Co-Authors: E. Kourkchi (IPM); Habib Khosroshahi (IPM); D Carter (ARI); B. Mobasher (UCR) Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: Rich environment of Coma galaxy cluster offers a unique environment to study many galaxy properties including dwarf galaxy scaling relations, such as the Fundamental Plane (FP) and Photometric Plane. We present a study of scaling relations for a large sample of dwarf galaxies in the core of Coma cluster down to -15 mag, for the first time, taking advantage of high resolution DEIMOS spectrograph on Keck II for measuring the internal velocity dispersion of galaxies and high resolution imaging of HST/ACS, which allows an accurate surface brightness modeling.
We find that the faint end galaxies in the sample show significantly higher velocity dispersion, for their optical luminosity, than expected from their more luminous counterparts thus resulting in a higher M/L. We also find that, the scatter about the FP depends on the faint-end luminosity cutoff, such that the scatter increases for fainter galaxies. The residual from the FP correlates with the galaxy colour, with bluer galaxies showing larger residuals from FP. We find that less massive dwarf ellipticals are bluer than their brighter counterparts, possibly indicating ongoing star formation activity. Although tidal encounters and harassment can play a part in removing stars and dark matter from the galaxy, we believe that the dominant effect will be the stellar wind associated with the star formation, which will remove material from the galaxy resulting in larger M/L ratios. We attribute the deviation of a number of faint blue dwarfs from the FP of brighter ellipticals to this effect. We explore the scatter around the Photometric Plane of the sample galaxies and show that, compared to the FP, the scatter about the photometric plane is smaller at the faint end. Structure of the Intermediate and High Velocity Clouds towards the LMC and SMC Author: Jonathan Smoker European Southern Observatory, Chile Co-Authors: A.J. Fox STSci
F.P. Keenan Queen's University Belfast Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: We present interstellar absorption-line spectroscopy of early-type stars in CaK and NaD towards the Large and Small Magellanic Clouds to investigate the large- and small-scale structure in foreground Intermediate and High Velocity Clouds (IHVCs). The data include FLAMES-GIRAFFE observations of 403 stars in four open clusters plus FEROS spectra of 52 in the LMC and 8 in the SMC.
From the FLAMES data we find that, within a 0.5 degree field-of-view, the CaII K equivalent width in the IHVC components varies by factors exceeding 10. A number of lines-of-sight toward NGC 1761 and NGC 2004 in the LMC show velocity structure in the IHVC gas, indicating multiple clouds are present along each
sightline, possible fragmentation of the clouds, or a two-phase medium. There are detections of molecular gas in LMC absorption towards a handful of sightlines, although no molecular detections are made in either IHVC or Galactic gas.
From the FEROS data we find CaII K IHVC absorption in around 60 per cent of sightlines. No NaI D is found at non-Magellanic HVC velocities aside from a tentative detection towards the star LHA 120-S 93. The lower limits on the CaII/NaI ratio in IHVCs are large, with a maximum value exceeding +1.5 dex,
illustrating the Routly-Spitzer effect. In four sightlines with previous
OI measurements,we find CaII/OI ratios in the LMC gas ranging from 0.23 to 1.3 dex below the solar value, indicating either dust or ionisation effects. Both CaII and HI data are available for three sightlines, with HVCs showing (a) similar CaII/HI ratios to the general IHVC population,and (b) identical CaII and HI velocities (within the errors), implying that at least in these
sightlines the two elements form part of the same structure.
The carbon star phase in the Sagittarius Dwarf Spheroidal Author: Iain McDonald Co-Authors: J.R.White (University of Manchester)
A.A.Zijlstra (University of Manchester)
J.Th.van Loon (Keele University)
G.C.Sloan (Cornell University)
E.Lagadec (ESO) Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: Carbon stars are an important source in the enrichment of heavy elements in galaxies. They help control the balance of carbon and oxygen in the interstellar medium and subsequent generations of stars, as well as changing the observed properties (colours, spectrum) of their host galaxies. Whether a star becomes carbon rich depends on its mass and metallicity, thus a galaxy's C/O ratio changes with time.
We have recently carried out a spectral survey of over 1000 stars in the Sgr dSph, whose population is close to the limit of carbon star production. I will discuss the carbon star population and its impact on the galaxy, and present the Sgr dSph in context with other local dwarf galaxies. The mass function of dwarf galaxies: Going beyond the Local Group with gravitational lensing Author: John McKean Co-Authors: S. Vegetti (MIT); D. J. Lagattuta (Uni. Melbourne); M. W. Auger (Uni. Cambridge); C. D. Fassnacht (Uni. California, Davis); L. V. E. Koopmans (Uni. Groningen) Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: Gravitational lensing provides an opportunity to measure the mass-fraction and the mass-function of low-mass substructure in massive galaxies well beyond the Local Group. I will review the gravitational lensing method of detecting substructures, which is independent of whether the substructure is luminous or not, from lensed quasar flux-ratio and astrometric anomalies. I will present new results from the ongoing SHARP project, which aims to image lensed quasar systems to search for luminous and dark substructures by searching for surface brightness anomalies in extended lensed images. The first major result from this survey is the detection of a low mass (2 x 10^8 M_sol) dark dwarf galaxy that is a companion of a massive early-type galaxy at redshift 0.881. I will also present the first constraints on the substructure mass-function for massive elliptical galaxies beyond the Local Group by combining this result with a previous detection. The nature of stars in the nucleus of M32 Author: Olivia Jones JBCA, University of Manchester Co-Authors: C. Kemper (ASIAA, Taiwan)
M. Rich (UCLA) Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: We investigate the infrared properties of cool, evolved stars in the local group dwarf elliptical galaxy M32 (NGC 221), using IRAC observations from the Spitzer Space Telescope. Our images resolve the dust-producing asymptotic giant branch population of M32 at 8 microns. These objects are highly enshrouded and have no apparent counterparts in the 1 micron WFPC2 HST images. Using IRAC colour information we can determine the nature of these dusty sources and through the comparisons of the 8 micron luminosity function with globular clusters the number of oxygen rich and carbon rich sources can be estimated giving clues to the global dust injection rate and the life cycle of matter on a galaxy wide scale. Here, we describe the program and present some first results. The Structure of the Sagittarius Stellar Stream as Traced by Blue Horizontal Branch Stars Author: Christine Ruhland Co-Authors: E. F. Bell (University of Michigan); H.-W. Rix (Max Planck Institute for Astronomy); X.-X. Xue (Max Planck Institute for Astronomy) Session: GAL3: The nature of satellite and dwarf galaxies Displayed during: Poster Session B Summary: We use a sample of blue horizontal branch (BHB) stars from the Sloan Digital Sky Survey Data Release 7 to explore the structure of the tidal tails from the Sagittarius Dwarf Galaxy. We use a method yielding BHB star candidates with up to ~70% purity from photometry alone. The resulting sample has a distance precision of roughly 5% and can probe distances in excess of 100 kpc. Using this sample, we identify a possible extension to the trailing arm at distances of 60-80 kpc from the Sun with an estimated significance of at least 3.8σ. Current models predict that a distant "returning" segment of the debris stream should exist, but place it substantially closer to the Sun where no debris is observed in our data. Exploiting the distance precision of our tracers, we estimate the mean line-of-sight thickness of the leading arm to be ~3 kpc, and show that the two "bifurcated" branches of the debris stream differ by only 1-2 kpc in distance. With a spectroscopic very pure BHB star subsample, we estimate the velocity dispersion in the leading arm, 37 km s-1, which is in reasonable agreement with models of Sgr disruption. A conservation law formulation of nonlinear elasticity in relativity for NS crust shattering Author: Stephanie J. Erickson Co-Authors: C. Gundlach (University of Southampton); I. Hawke (University of Southampton) Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Tidal shattering of neutron star crusts is expected to play a role in the dynamics of binary neutron star mergers, giving rise phenomena such as energetic gamma-ray bursts. For this reason, we have developed a general relativistic conservation-law formalism for nonlinear elasticity; this allows us to use high-resolution shock-capturing methods to resolve strong shocks. We hope to use this formalism to simulate the evolution of discontinuities in the crust of a neutron star caused by shattering and refreezing of the crust, thus illuminating the role this process may play in the evolution of a binary neutron star system. A New Method to Reduce Eccentricity in Numerical-Relativity Simulations of Black-hole-Binary Inspira Author: Michael Puerrer School of Physics & Astronomy, Cardiff University Co-Authors: S.Husa (Departament de Fisica, Universitat de les Illes Balears, Palma, Spain)
M.Hannam (School of Physics & Astronomy, Cardiff University, UK) Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: We present a new iteration method for producing low-eccentricity of black-hole-binary simulations. Given reasonably low eccentricity starting momenta for puncture initial data we evolve these data numerically for 3-4 orbits and construct improved initial parameters by comparing numerical relativity with post-Newtonian quantities. We can reach eccentricities below ~0.001 in one or two iteration steps. We also comment on the difference between the eccentricities calculated from the orbital motion and the GW signal. Black hole binaries galactic and intergalactic globular clusters Author: Jonathan Michael Blake Downing ARI, Zentrum für Astronomie der Universität Heidelberg Co-Authors: Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Mergers of black hole binaries are one of the most promising sources for the next generation of ground-based gravitational wave detectors. Black hole binaries are a rare outcome of stellar evolution but can be produced efficiently by dynamical interactions in globular clusters. I will present a summary of a large set of Monte Carlo globular cluster simulations that show that black hole binary detection rates will be dominated by binaries produced in star clusters. I will also present first results for the black hole binary population in intergalactic globular clusters, such as those recently found in Coma, that have not been taken into account in previous black hole binary population synthesis studies. Genuine field theory needed to support Gravitational Waves Author: Max K Wallis Co-Authors: T.W.Marshall Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Our theme is that gravitational waves necessitate the gravitational field having material status, like the electromagnetic field of Faraday-Maxwell, which motivated the gravity mass/energy term in Einstein’s field equation. To properly formulate gravitational theory as a field theory, we need a real (not pseudo-) tensor for gravitational energy-momentum, as recognised by Hilbert and accomplished by Weinberg. Implicit in Einstein's derivation of quadrupole radiation was that the gravitational field is carried by the Minkowski space of ‘special’ relativity. Babak & Grishchuk etc. have developed this field interpretation of gravity to explicitly include the Minkowski metric in the field equations. Field theorists commonly demand covariance, gauge invariance and the Principle of Equivalence - we argue for maintaining the first, abandoning the second, and accepting only the weakest form of the third (Eötvös Principle). Gravitational waves being real rather than a metric fluctuation followed from the orbit decay of the Hulse-Taylor double pulsar, at the rate predicted by Einstein’s quadrupole formula. Yet few challenge the view of gravity as only geometry and the catch-phrase “Space tells matter how to move” coupled to “matter tells space how to curve” persists. The material nature of gravitational energy and gravitational waves shows instead that “fields tell matter how to move”. Optical rigidity concepts at the Glasgow 10m prototype interferometer Author: John Macarthur Co-Authors: J. Macarthur (University of Glasgow), B.W. Barr (University of Glasgow), M.P. Edgar (University of Glasgow), S. Hild (University of Glasgow), S. Huttner (University of Glasgow), B. Sorazu (University of Glasgow) and K. A. Strain (University of Glasgow) Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Ground based gravitational wave detectors are currently undergoing a major upgrade expected to improve sensitivity in their detection band by a factor of 10. As a result quantum noise, made of shot noise and radiation pressure noise, will become the dominant noise source across most of the frequency band. The obvious improvement consists of increasing laser power to reduce shot noise at high frequency, which in turn inescapably gives rise to a larger radiation pressure effect at low frequency. However, using innovative interferometer topologies, this effect can be used to our advantage by creating coupling of the cavity mirrors via the pendulum restoring force to the radiation pressure force, also known as the Optical Spring effect. This and other optical rigidity schemes can significantly surpass the Standard quantum limit and are going to become vital for future gravitational wave detectors. We will give an overview on the experimental testing of optical rigidity concepts at the Glasgow 10m prototype interferometer. Optimal use of astrophysical priors for electromagnetic follow-ups of gravitational wave candidates Author: Will Vousden Co-Authors: I. Mandel (University of Birmingham) Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Current methods for locating EM counterparts to GW events generated by neutron star binary mergers rely on several optimistic assumptions regarding their distribution and genesis. However, due to the rarity of detectable GW events that will yield observable counterparts, it is important that the preciseness of sky location priors is commensurate with our confidence in their correctness.
I will present an analysis of the effects on EM follow-up success rates of the choice of astrophysical priors, tested against simulated distributions of candidate events under a range of corresponding astrophysical models. It is expected that successful follow-ups will deliver rich insight into the underlying astrophysics of compact binary mergers. Searching for Gravitational waves associated with Gamma-ray bursts Author: Thomas Adams Co-Authors: Thomas Adams for the LIGO collaboration and VIRGO collaboration Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Gravitational waves (GWs) are oscillations in the gravitational field which propagate at the speed of light and are emitted by accelerated masses. Gamma-ray bursts (GRBs) are intense flashes of gamma rays which can be grouped into two classes by their duration and spectral hardness. The progenitors for short-hard GRBs (duration < 2s) are thought to be neutron star binaries or neutron star black hole binaries, while long-soft GRBs (duration > 2s) are associated with core-collapse supernovae. These objects are compact, asymmetric, relativistic and emit large amounts of energy in a short period of time which makes them likely sources for GWs. Using data from the LIGO, VIRGO and GEO detectors an unmodelled "burst" search for GWs associated with GRBs observed by the SWIFT, FERMI and IPN satellites was performed. We give the status of this search and look at prospective searches for the advanced detector era. Status of the ground based interferometric gravitational wave detector GEO 600 Author: Borja Sorazu Co-Authors: GEO team. Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: GEO 600 is the German-British contribution to the first world network of ground based, large scale, interferometric gravitational wave detectors in operation during the last decade. In 2009 this detector initiated an upgrade program, called GEO-HF, which targeted an improvement of around one order of magnitude in its measurement sensitivity at the high frequencies where the limiting factor is photon shot-noise.
We present a review of the current status of this upgrade, focusing on the main techniques being implemented; homodyne readout and output mode cleaner (OMC) installation, transition to tuned signal recycling, laser power increase and injection of squeeze vacuum states. We also report on our efforts on detector commissioning and characterisation.
The status of galactic neutron star searches using gravitational waves Author: Matthew Pitkin Co-Authors: The LIGO Scientific Collaboration; The Virgo Collaboration Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Rotating neutron stars are expected to be weak emitters of quasi-monochromatic gravitational waves. Data from the initial generation of interferometric gravitational wave detectors, LIGO and Virgo, have been used to search for such sources. We present a status report on these, including searches for specific targets, such as known pulsars and supernova remnants, and blind all-sky searches for unknown sources. We will also examine the prospects for future searches using the Advanced LIGO and Virgo detectors. Transient gravitational waves at r-mode frequencies associated with pulsar glitches Author: Ignacio Santiago-Prieto Co-Authors: Ik Siong Heng (University of Glasgow); D.I. Jones (University of Southampton); James Clark (University of Massachusetts, Amherst) Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Pulsar glitches can cause oscillations in the fluid interior of the pulsar which lead to gravitational wave emissions at the r-modes frequencies of the neutron star. The emitted gravitational waves can have long damping time scales, ranging from minutes to days. We estimate the strength of the emitted gravitational waves from potential sources and demonstrate their detectability for future detectors through simulated data, using parameters derived from radio and X-ray observations. What we (don't) know about gravitational waveforms from black-hole binaries Author: Frank Ohme Co-Authors: Session: GW1: Dawn of Gravitational Astronomy Displayed during: Poster Session A Summary: Accurately predicting the complete gravitational-wave signal of coalescing
black-hole binaries is of fundamental importance in the efforts to detect and
correctly interpret these signatures in the data of current and future
detectors. The best waveform models today combine information from both
analytical and numerical calculations into complete inspiral-merger-ringdown
waveforms, and I will review the current status of such models. I will
particularly focus on the question of how reliable these models are and which
statistical and systematic bias we have to expect when using these template
waveforms to estimate the source parameters of the signal. A black hole transient, and other X-ray binaries in Cen A Author: Mark Burke Co-Authors: Somak Raychaudhury (University of Birminham), Ralph Kraft (Harvard-Smithsonian Center for Astrophysics), + Cen A VLP collaboration Session: HE1: Extragalactic Transients Displayed during: Poster Session A Summary: We model the X-ray spectra of point sources in the nearby early-type galaxy NGC 5128 (Cen A), focussing on the discovery of a bright X-ray transient, CXOU J132527.6-430023. The source was first detected over the course of six 100 ks Chandra observations in 2007, reaching an unabsorbed outburst luminosity of 1-2*10^38 erg/s in the 0.5-7.0 keV band before returning to quiescence. Such luminosities are possible for both stellar-mass black hole and neutron star X-ray binary transients. The brightness of the source after a >100 fold increase in flux, coupled with the results from spectral fitting appear to lend weight to the view that this is a black hole transient observed in the thermally dominant state. We discuss this result in the context of our work modelling all of the bright X-ray binaries in Cen A that were observed in deep Chandra pointings. The proximity of the galaxy combined with the depth of the data will lead to this being the largest spectral investigation of X-ray binaries outside of the Local Group, while correlation with the large globular cluster population will provide new insights into binary formation and evolution. A Stacked Analysis of Cluster-centre AGN with Fermi-LAT Data Author: Kate Dutson Co-Authors: R. J. White (University of Leicester)
A. C. Edge (University of Durham)
J. A. Hinton (University of Leicester) Session: HE1: Extragalactic Transients Displayed during: Poster Session A Summary: Radio-synchrotron and hard X-ray emission establish clusters of galaxies as hosts to significant populations of non-thermal particles, and it is believed that feedback from the central active galactic nucleus (AGN) plays a crucial, cluster-scale role in accelerating these particles, and counteracting the observed cooling flow; driving weak shocks through the intracluster medium and inflating bubbles of relativistic plasma tens of kiloparsecs in extent. Observational evidence for variable high-energy (HE) γ-ray emission associated with the central engine of a number of clusters supports this view.
Motivated by Fermi-LAT detections of active galaxies such as NGC 1275 and M87 (the dominant members of the Perseus and Virgo clusters, respectively), we present a radio-selected sample of 63 such Brightest Cluster Galaxies (BCGs) within cooling-core clusters, treating each as a candidate source of ~GeV γ rays. The standard Fermi-LAT analysis procedure is augmented by a source-specific normalisation of the diffuse γ-ray background, and following a maximum likelihood fitting of the data, the distribution of Test Statistic values across the sample is studied. The counts and model maps for candidate sources below an appropriate critical statistical significance are stacked: imitating a deeper observation of the BCG class than is currently achievable in HE γ rays.
CLASP (Create Lightcurves with Alignment, Subtraction and Photometry) Author: Joe Lyman Liverpool John Moores University Co-Authors: D.F.Bersier (Liverpool John Moores University)
P.A.James (Liverpool John Moores University)
Session: HE1: Extragalactic Transients Displayed during: Poster Session A Summary: CLASP (Create Lightcurves with Alignment, Subtraction and Photometry) comprises two pipelines developed to automate data reduction and lightcurve creation from SNe imaging through template subtraction.
Images are cleaned, then accurate alignment is achieved between a science image containing the SNe and a template image. Subtraction of the template light from the science image, after seeing and flux matching, is performed utilising a version of the ISIS routine of Alard (2000). The subtracted image permits accurate photometry of faint SNe, whose significant host galaxy light would compromise photometry otherwise. Photometry is performed on the subtracted image and calibrated using the science and template images, allowing lightcurves to be created with minimal user interaction required.
The pipelines have been extensively tested on Liverpool Telescope data for instruments with FOVs ranging from 5 arcminutes to 1 degree, performing well in the vast majority of cases; other telescope data are also accepted. With huge amounts of observational follow-up being performed for surveys such as PTF, as well as the intense monitoring of individual SNe that is feasible presently, the quick and automated nature of these pipelines make them equally invaluable to both large data sets and individual objects.
A catalogue of multi-colour, pseudo-bolometric lightcurves of Liverpool Telescope observations of PTF CCSNe is being created using these pipelines. These lightcurves allow analytical extraction of the physical parameters (ejected mass, mass of nickel-56 and kinetic energy) of the explosions for a sample of CCSNe of unprecedented size. This will allow investigation into trends of these parameters across CCSNe subtype and host properties, thereby probing the progenitor systems of CCSNe in combination with further constraints from environment measures.
Long-term X-ray variability of Swift J1644+57 Author: Roberto Soria Co-Authors: C.J. Saxton (MSSL), K. Wu (MSSL), N.P.M. Kuin (MSSL) Session: HE1: Extragalactic Transients Displayed during: Poster Session A Summary: Exactly 1 year ago, the nuclear black hole in a galaxy at redshift 0.35 went into outburst, blazing a jet along our line of sight; this increased activity was interpreted as the result of a tidal disruption event. We studied the decline of the X-ray flux over the following months, and noticed a series of dips recurring on characteristic timescales (eg 4.5E5 s) and their harmonics. We show that the dips have a softer X-ray spectrum but no additional absorption; this rules out obscuration from orbiting clouds. We propose that the dips are caused by temporary, partial loss of alignment with the (wobbling) jet axis, so that sometimes we only see emission from a slower, less collimated part of the outflow. The existence of a pattern of characteristic timescales in the dipping behaviour may be due to a combination of jet precession and nutation. FR dichotomy, accretion modes and environmental factors in the local Universe Author: Melanie Gendre Co-Authors: P. N. Best (IfA Edinburgh); J. V. Wall (UBC) Session: HE2: The Gamma-ray/radio connection Displayed during: Poster Session A Summary: Active galactic nuclei (AGN) comprise the majority of currently observed radio galaxies, and the Fanaroff-Riley (FR) categorisation provides a classification of extended AGN. The FRI objects have the highest surface brightness along the jets near the core, while FRII sources show the highest surface brightness at the lobe extremities, as well as more collimated jets.
This FR dichotomy is based purely on the appearance of the radio objects, and the mechanisms differentiating the two populations are still unknown. Two main streams of models exist to explain these differences in morphology. Extrinsic models are purely based on the source environment, where inter-galactic medium density is the differentiating factor: jets of sources in higher/lower density mediums experience a higher/lower degree of resistance, yielding sources with FRI/FRII structures respectively. Intrinsic models, on the other hand, suggest that the dichotomy arises from differences in the properties of the central black hole. In these scenarios, low-excitation galaxies (LEG) have jets produced by low accretion-flow rate which are generally weak and mostly display FRI-type structure, whereas high-excitation galaxies (HEG) have higher accretion flow rates giving rise to stronger, mainly FRII-type jets. If the FR dichotomy was fully dependent on the jet properties, FRI/II sources would be systematically associated with LEG/HEG respectively. However, in several cases, small subsets of FRIs were found in HEG samples, as well as some FRIIs being associated with LEGs.
The presented work is based on the CoNFIG catalogue, a sample of radio sources at 1.4-GHz, including FRI/FRII/Compact morphology classifications, optical identifications and redshift estimates. High/low excitation classification and environmental richness factor of a subsample of local (z<0.3) CoNFIG extended galaxies were compiled to investigate the possible FR morphology-accretion mode-environment relations. The sub-sample contains 208 sources, including 75 FRIs and 108 FRIIs, 76% of which have available spectra, mostly from SDSS.
We found that there is a broad overlap of properties, although FRIs generally reside in denser environments that FRIIs. More interestingly, a source found in a rich environment has a very high probability of being both LEG and FRI, fitting with scenarios in which cooling occurs from the X-ray halo. In addition, FRIs broadly show the same RLF shape in all 4 classes (poor/rich HEG/LEG), while FRIIs show more evidence for a switch between HEGs at high luminosities to LEGs at low luminosities. Radio observations of unidentified Fermi LAT sources Author: Ewan Barr Co-Authors: L. Guillemot, D. Champion, M. Kramer and R. Eatough (MPIfR) Session: HE2: The Gamma-ray/radio connection Displayed during: Poster Session A Summary: In the 4 years since its launch, the Large Area Telescope (LAT) aboard
Fermi has revolutionised gamma-ray astronomy. However, due to a low
number of incident gamma-ray photons, it is not possible to identify
many of the sources discovered by the LAT. This is especially true for
binary pulsars, where orbital motion may obfuscate periodicities. Our
solution is to perform sensitive pulsar searches at radio wavelengths
at the position of the gamma-ray source, a technique which has, to
date, found 36 new millisecond pulsars (MSP).
Here we present an overview of the current efforts to further
understand the population of radio selected LAT pulsars, with
particular focus on a 1.4 GHz targeted search in LAT error boxes
performed with the 100-m Effelsberg telescope. This search, the
largest of its type, covered 289 unidentified sources with > 200
hours of telescope time.
In addition to the discovery of the "Black Widow" MSP, PSR J1745+1017,
this survey has provided strong luminosity and spectral index limits
on several newly detected radio and gamma-ray pulsars.
Furthermore, with the large number of sources covered in this work we
have performed a statistical analysis of the population distribution of
radio selected LAT pulsars. Radio variability of Fermi gamma-ray loud AGNs and S_gamma - S_radio correlations Author: Emmanouil Angelakis Max-Planck-Institut für Radioastronomie Co-Authors: L. Fuhrmann(1), V. Pavlidou(1), I. Nestoras(1), R. Schmidt(1), J. A. Zensus(1), T. P. Krichbaum(1), H. Ungerechts(2), A. Sievers(2), D. Riquelme(2), L. Foschini(3)
1: Max-Planck-Institut für Radioastronomie, Bonn, DE
2: Instituto de Radio Astronomía Milimétrica, Granada, Spain
3: INAF - Osservatorio Astronomico di Brera, Merate, Italy Session: HE2: The Gamma-ray/radio connection Displayed during: Poster Session A Summary: It has always been thought that two types of Active Galactic Nuclei, namely Blazars and Radio Galaxies, are strong gamma-ray emitters. The recent discovery of gamma-ray emission from Narrow Line Seyfert 1 galaxies by Fermi/LAT, revolutionises , among others, the belief that jet emission is exclusively associated with old elliptical galaxies. The F-GAMMA program with its unprecedented radio frequency coverage, fast observing cadence, and long time baselines, allows us the detailed study of the variability characteristics and properties of their radio jet emission. Here we present the most recent results of the F-GAMMA monitoring and compare their variability characteristics with the rest of the targeted Fermi blazars.
Among the most debated topics, on the other hand, in AGN research is the correlation between the radio and the gamma-ray emission. Several claims have been made with respect to possible connections between radio to gamma-ray fluxes and luminosities, relations which are know to be subject to severe biases influences. Here, a statistically robust method for the evaluation of the significance of such a correlation between F-GAMMA radio and Fermi/LAT gamma-ray 1FGL flux is presented and it is argued that, in certain cases, such correlations hold; indicating that a possible intrinsic connection in the production of radio and gamma-ray photons, may be at play.
Recent Galactic Results from the VERITAS Collaboration Author: Gareth Hughes Co-Authors: VERITAS Collaboration Session: HE2: The Gamma-ray/radio connection Displayed during: Poster Session A Summary: The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground-based gamma-ray observatory, located in southern Arizona, sensitive to energies from 100GeV up to 30TeV. VERITAS has been fully operational since 2007 and the current sensitivity enables the detection of a 1% Crab Nebula flux at 5 sigma in under 30 hours. The scientific observations include a strong galactic program. Objects observed comprise of pulsars, PWNe, HMXB and sources with unknown counterparts in other wavelengths. This talk will review the status of the current galactic science results.
LOFT - Large Observatory for X-ray Timing Author: Dr Silvia Zane Co-Authors: Jan-Willem den Herder, Marco Feroci, Enrico Bozzo,
Luigi Stella, Michiel van der Klis on behalf of the LOFT Team
Silvia Zane, Roberto Mignani, Dave Walton, Tom Kennedy, on behalf of the MSSL-LAD team
Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: LOFT is one of the four M3 missions that have been selected by ESA for an
Assessment Phase with launch in 2020-2022. LOFT is specifically designed
to study the very rapid X-ray flux and spectral variability that directly
probe the motion of matter down to distances very close to black holes and
neutron stars. A 10 m2-class instrument in combination with good spectral
resolution (<260 eV around 6 keV) is required to exploit the relevant
diagnostics and holds the potential to revolutionise the study of
collapsed objects in our galaxy and of the brightest supermassive black
holes in active galactic nuclei. High-time-resolution X-ray observations of compact objects are unique in providing direct access to strong-field gravity, black hole masses and spins, and the equation of state of ultra-dense matter.
LOFT will carry two main instruments: a Large Area Detector (LAD, to be
built at MSSL with the collaboration of Leicester for the collimator) and
a Wide Field Monitor (WFM). The ground-breaking characteristic of the LAD
(that will work in the energy range 2-50keV) is a mass per unit surface in
the range of ~10 kg/m2, enabling an effective area of ~10 m2 (@10 keV) at
a reasonable weight and improving by a factor of ~20 over all
predecessors. This will allow timing measurements of unprecedented
sensitivity, allowing for instance the capability to measure the mass and
radius of neutron stars with ~5% accuracy, or to reveal blobs orbiting
close to the marginally stable orbit in active galactic nuclei. The LOFT
scientific payload is completed by the coded-mask WFM, for monitoring a
large fraction of the sky potentially accessible to LAD, to provide the
history and context for the sources observed by LAD and trigger its
observations on their most interesting and extreme states.
In this poster, we will illustrate the scientific goals and the unique
potential of the mission and the major role played by MSSL and UK
scientists in the LOFT team.
Magnetars are super hot and super cool Author: Wynn C.G. Ho Co-Authors: K.Glampedakis (Universidad de Murcia); N.Andersson (University of Southampton) Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: We examine to what extent the inferred surface temperature of magnetars in quiescence can constrain the presence of a superfluid in the neutron star core and the role of magnetic field decay in the core. By performing detailed simulations of neutron star cooling, we show that extremely strong heating from field decay in the core cannot produce the high observed surface temperatures nor delay the onset of neutron superfluidity in the core. We find that it is not possible to conclude that magnetar cores are in a non-superfluid state purely from high surface temperatures, and we find that neutron superfluidity in the core occurs less than a few hundred years after neutron star formation for core fields < 10^16 G. Thus all known neutron stars, including magnetars, without a core containing exotic particles, should have a core of superfluid neutrons and superconducting protons. Optical Monitoring of the Black Hole X-Ray Binaries, XTE J1118+480 and GX 339-4 Author: Fraser Lewis Co-Authors: D.M. Russell (Amsterdam, IAC) Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: We present results from the long-term optical monitoring of these two black hole X-Ray Binaries using the Faulkes Telescopes North and South. These two 2-metre facilities (in Hawai'i and Australia) have allowed us to undertake regular monitoring of these sources in V, R and i' bands. The flexibility of our monitoring campaign allows us to alter the cadence of our observations in response to outbursts or state transitions within these systems.
We show that the long-term (~ 5 years) variability of XTE J1118+480 can be accounted for by just the variability of its (orbital) ellipsoidal modulation. We also show that the system is bluer when brighter comensurate with emission from an accretion disc.
We discuss results from short-term variability studies of GX 339-4 in outburst and during its fades towards quiescence and show that the rms variability in the optical is state dependent as seen at X-ray wavelengths.
Short period variables in the Kepler field Author: Adam Brooks Co-Authors: Gavin Ramsay (Armagh Observatory); Thomas Barclay (NASA-Ames Research centre); Pasi Hakala (FINCA, Tuorla Observatory, Finland) Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: In the summer of 2011 we commenced a deep, high cadence, photometric survey of the Kepler field using the Isaac Newton Telescope (INT) on La Palma. We take a series of 20 sec exposures in the g band lasting one hour. Light curves are obtained for all sources in the field and those which are variable, identified. We are sensitive to objects in the range 13.5 The Proper Motion of the Central Compact Object RX J0822-4300 in the Supernova Remnant Puppis-A Author: Werner Becker Max-Planck-Institut für extraterr. Physik Co-Authors: T.Prinz (Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85741 Garching, Germany), P.Frank Winkler (Department of Physics, Middlebury College, Middlebury, VT 05753), R.D.
Petre (NASA Goddard Space Flight Center, Greenbelt, MD 20771) Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: Using the High Resolution Camera (HRC) aboard the Chandra X-ray satellite we have re-examined the proper motion of the central compact object RX J0822-4300 in the supernova remnant Puppis A. New data taken in summer 2010 along with three additional archival data sets, of which the oldest dates back to December 1999, provide a baseline of 3886 days (more than 10 1/2 years) to perform the measurement. Correlating the four positions of RX J0822-4300 as measured in each data set implies a projected proper motion of m_u ~69 mas/yr (preliminary). For a distance of 2 kpc this proper motion is equivalent to a recoil velocity of ~ 650 km/s. The position angle is found to be 242.5±7.0 degrees. Both the magnitude and direction of the proper motion are in agreement with the birth place of RX J0822-4300 being near to the optical expansion center of the supernova remnant. For a displacement of 371 ± 8 arcsec between its birth place and today's position we deduce an age of 5170 ± 650 yrs for RX J0822-4300 and hence for the supernova remnant Puppis A. Understanding X-ray Reflection in AGN Author: Dan Wilkins Institute of Astronomy, University of Cambridge Co-Authors: A.C. Fabian (Institute of Astronomy, University of Cambridge) Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: High quality X-ray observations of AGN reveal a number of spectral features resulting from the reflection of X-ray continuum emission from a source in a corona surrounding the central black hole off the accretion disc. These features include the prominent iron K emission line at 6.4keV, broadened by relativistic effects close to the black hole and can probe right down to the event horizon. Detailed analysis of the emission line profile reveals the illumination pattern of the accretion flow by the X-ray source (the emissivity profile), which depends on a number of factors including the location and geometry of the primary X-ray source.
Observed emissivity profiles are naturally explained by general relativistic effects on the rays and the accretion disc. Comparing observed emissivity profiles to systematic, high performance GPU-based ray tracing simulations relates the emissivity profile to the properties of the X-ray source. When combined with measurements of reverberation time lags, constraints can be placed on the location and geometry of the coronal X-ray sources in AGN from observed emissivity profiles. Such analysis has been completed for the narrow line Seyfert 1 galaxy 1H 0707-495 and other sources, revealing the location and extent of the primary X-ray source.
What is feeding the intermediate-mass BH candidate HLX1? Author: Roberto Soria Co-Authors: P.J. Hakala (FINCA), G.K.T Hau (ESO), J.C. Gladstone (Alberta), A.K.H. Kong (NTHU), G Dubus (Grenoble) Session: HE3: Multi-wavelength observations of compact objects Displayed during: Poster Session B Summary: HLX1 is the strongest candidate proposed to date for an intermediate-mass black hole. It showed 3 FRED-like X-ray outbursts in the last 3 years, almost exactly one year apart. The peak X-ray luminosity of all 3 outbursts is about 1E42 erg/s, decreasing to about 3E40 erg/s between outbursts. We observed the optical counterpart with the VLT, during the decline from the 2010 and 2011 outbursts, and compared it with the HST observations of Dr Sean Farrell & collaborators, obtained closer to outburst peak. We argue that the optical luminosity declines along with the X-ray luminosity. Hence, we suggest that at least the blue/UV optical emission is mostly due to the accretion disk rather than a massive cluster of young stars around the BH. We propose that the BH is fed by a long-period pulsating star, as an alternative to the eccentric orbit scenario. Interference Mitigation schemes for LOFAR dynamic spectra Author: Dr. Ashish Asgekar ASTRON, Netherlands Institute for Radio Astronomy Co-Authors: R.A. Fallows (ASTRON, the Netherlands Institute for Radio Astronomy, & Institute of Mathematics and Physics, Aberystwyth University, Penglais Campus, Aberystwyth, SY23 3BZ, Wales, UK);
S. ter Veen (Department of Astrophysics, University of Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands) Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results Displayed during: Poster Session B Summary: We present details of LOw Frequency ARray (LOFAR) dynamic spectrum data pipeline, focussing on the mitigation of Radio Frequency Interference (RFI) in the data sets. RFI can be categorised in two forms: persistent interference where entire frequency channels can be regarded as contaminated, and brief pulses where single spikes of RFI can exist at more random times and frequencies. The worst-affected frequency channels are identified using median filters. Most of the persistent interference can be identified in this way, allowing the median of each frequency channel to be interpolated in frequency across the 'bad’ channels. This creates an estimate of the telescope response across the pass-band, which is used to 'flatten’ the data. Two-dimensional (2-D) median filters are then employed to locate the remaining (more random) spikes of RFI. We also describe a method of "random substitution” to obtain 'clean' time-frequency data after RFI identification and mitigation. This may allow the calculation of bi-spectra and the development of novel ways to study interplanetary scintillation (IPS) and solar wind micro structure. Lightning at Saturn and Jupiter radiation belts emission seen by LOFAR Author: Julien Girard LESIA - Observatoire de Paris, France Co-Authors: Griessmeier J.-M. (LPC2E - Université d'Orléans, France); Hess S. (LATMOS/IPSL, France); Majid W. (JPL Caltech, USA); Tasse C. (GEPI - Observatoire de Paris, France); Zarka P. (LESIA - Observatoire de Paris, France) Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results Displayed during: Poster Session B Summary: The Planetary Working Group of the LOFAR Transient Key Project: "Planets & exoplanets" currently works with the LOFAR radiotelescope time-frequency data taken in phased array mode and interferometer mode. Commissionning observations were performed on Saturn lighting and on Jupiter emissions in meter-decameter range.
Along with the detection of Saturn lightning (Saturn Electrostatic Discharges - SED) in the LBA band (30-90 MHz) at high time resolution, the characterization of SED (burst duration, power spectrum, etc.) will deepen our understanding of these events as compared to their terrestrial counterparts (Farrell et al., 2007 and ref. therein).
In addition, Jupiter was observed in the HBA band (110-250 MHz) in interferometer mode. The exploitation of these interferometric data leads to the first high resolution images of Jupiter's synchrotron emission from its radiation belts that will reveal the spatial structure of this emission at low frequencies (see also de Pater, 2004).
An update on current work will be presented. LOFAR Imaging of Cygnus A Author: John McKean Co-Authors: the LOFAR collaboration Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results Displayed during: Poster Session B Summary: The nearby radio galaxy Cygnus A is the brightest source in the low frequency sky that will be observed with LOFAR. Therefore, Cygnus A provides an excellent commissioning target to test the LOFAR system and also to produce the first science results. I will present new imaging of Cygnus A with LOFAR between 30 and 240 MHz, with baselines of up to ~100 km. These data provide the highest angular resolution images of Cygnus A at low frequencies to date. I will present a preliminary spectral analysis of the source, including the properties of the lobes, hot-spots and their interaction with the intergalactic medium surrounding the galaxy. LOFAR, Weather and the implications for EISCAT_3D and the SKA. Author: Derek McKay-Bukowski Rutherford Appleton Laboratory Co-Authors: Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results Displayed during: Poster Session B Summary: The LOFAR (Low-Frequency Array) system makes use of mass-produced, relatively-cheap antennas deployed in a wide variety of different site environments. Apart from the challenges of varying local geology, layout and infrastructure, each presents its own unique weather conditions. With several years of experience (and some failures and damage), we are now in a position to assess the physical performance of the design and look at the implications of our findings on long-term LOFAR operations as well as other planned phased-array systems such as EISCAT_3D and the Square Kilometre Array (SKA). Solar Observations with LOFAR Author: Christian Vocks Leibniz-Institut für Astrophysik Potsdam Co-Authors: F. Breitling; G. Mann Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results Displayed during: Poster Session B Summary: During the first commissioning phase of the LOw Frequency ARray (LOFAR), the Key Science Project "Solar Physics and Space Weather with LOFAR" has developed a pipeline for solar imaging. Solar radio radiation in the LOFAR frequency range of 30 - 240 MHz emanates from the outer layers of the Sun's hot atmosphere, the corona. Strong scattering of radio waves due to coronal turbulence limits the angular resolution of any radio image to a few 10s of acrseconds. This corresponds to baselines between the core and the nearest remote stations of LOFAR. Solar imaging is largely based on the standard imaging pipeline, but the Sun as a bright, extended, and temporally variable source poses special challenges for the calibration of LOFAR data. Different calibration strategies, e.g. using only the shortest baselines or solution transfer from external calibration sources, will be discussed. Radio images of the Sun will be shown, both for LOFAR's low and high frequency band, that were taken during commissioning runs in the year 2011. This includes the first LOFAR observation of a solar radio burst. Observation plans for LOFAR's first operational phase will be presented. The First Detection of a Coronal Mass Ejection (CME) with LOFAR Author: M.M. Bisi Institute of Mathematics and Physics, Aberystwyth University Co-Authors: R.A. Fallows (Institute of Mathematics and Physics, Aberystwyth University/ASTRON, the Netherlands Institute for Radio Astronomy), and A. Asgekar (ASTRON, the Netherlands Institute for Radio Astronomy). Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results Displayed during: Poster Session B Summary: Interplanetary scintillation (IPS) is a powerful means of observing the Sun’s extended atmosphere – the solar wind – through remote sensing. IPS – the twinkling of radio waves from a distant, compact, astronomical natural radio source – results from density inhomogeneities traversing the interplanetary medium moving outward from the Sun. Using the newly-developed IPS experiment on the novel European-based radio telescope, the LOw Frequency ARray (LOFAR), we have our first detection of a coronal mass ejection (CME) passing through one of our preliminary observations of IPS during the ongoing commissioning phase of the LOFAR system. Here, we identify the CME in white-light imagery, and briefly discuss and compare its characteristics/properties with other sources of data where available. We also note how such work will be taken forward with on-going test observations of IPS using LOFAR, and look to the future to fully combine LOFAR observations of IPS with those taken using other systems worldwide, including the European Incoherent SCATter (EISCAT) radar and the Multi-Element Radio-Linked Interferometer Network (MERLIN) which are also located within Europe along with LOFAR. A 19-pixel L-band receiver array for FAST. Author: Bruno Maffei Jodrell Bank Centre for Astrophysics Co-Authors: Rendong Nan (NOAC), Jin Chengjin (NAOC), Graeme Carrad (CSIRO) and the FAST collaboration. Session: INS5: Radio to sub-millimeter technology developments for receiver arrays Displayed during: Poster Session B Summary: The FAST (Five hundred meter Aperture Spherical Telescope) project is being developed by China. This approved mega-science currently under construction will be the largest single dish telescope ever built. This facility, planned to be commissioned in 2016, will largely surpass the capabilities of the famous Arecibo telescope leading to a formidable tool for the study of pulsars, HI regions and more generally Cosmology. Several receivers will be installed at its focus on a common platform. A consortium of three institutes (JBCA-UK, NAOC-China and CSIRO- Australia) has been formed in order to develop the first set of receivers for this world leading facility. This 19-pixel L-Band receiver array (0.95 – 1.45 GHz), which will be ready for the telescope commissioning, will give the first light of this facility which is expected to be a new milestone for the pulsar search and pulsar timing study. We present the design of the telescope together with the expected performance of the L-Band receiver array. Generation of vortex beams in the W-band: design and testing of a dielectric q-plate. Author: Stefania Maccalli Co-Authors: G. Pisano (JBCA); R. Ng (JBCA) Session: INS5: Radio to sub-millimeter technology developments for receiver arrays Displayed during: Poster Session B Summary: It has been discovered recently that light can carry not only the usual Spin Angular Momentum (SAM), associated with circular polarization states of the field, but also Orbital Angular Momentum (OAM): light beams carrying quantized values lħ of OAM are called optical vortices. This kind of radiation has a wide range of applications: from quantum encryption and telecommunications to non-contact manipulation of matter and astrophysics.
The goal of our project is to develop instrumentation able to discern different OAM states in the laboratory, at millimetre wavelengths (W-band). This can be achieved by designing devices such as q-plates: artificial birefringent plates designed for production/detection of particular OAM states. Here we present the RF characterisation of one prototype of dielectric q-plate that has been designed to produce/detect POAM beams with charge l=+/-2. All the measurements were carried out using a Vector Network Analyser (VNA). The measured beam pattern resulted in very good agreement with the finite-element analysis predictions (HFSS) showing both the expected intensity annular shape and the phase change of 4pi across a close loop around the propagation axis. Instrumental systematic effects of quasi-optical components for astronomical instruments Author: Ho-Ting Fung JBCA, The University of Manchester Co-Authors: H.Fung(JBCA, The University of Manchester); F.Ozturk(JBCA, The University of Manchester); B.Maffei(JBCA, The University of Manchester); G.Pisano(JBCA, The University of Manchester) Session: INS5: Radio to sub-millimeter technology developments for receiver arrays Displayed during: Poster Session B Summary: Astrophysical experiments dedicated to millimetre-wave polarimetry, in particular COrE and QUBIC, are in need of well defined antenna beam shapes. Such beams not only have to be modelled with care, but they must also be characterised accurately. Some of the quasi-optical components within these instruments (such as interference filters and half wave plates) can modify the shape of the antenna beams. We present here, the measurements and simulations of such effects (co- and cross- polarisation radiation patterns) on a corrugated horn antenna beam, using a Vector Network Analyser at W–band (75 – 110 GHz). Investigation of Optimised Horns for use in Future Arrays, as an Alternative to Corrugated Horns Author: Darragh McCarthy National University of Ireland, Maynooth Co-Authors: N.Trappe(National University of Ireland, Maynooth); B.Maffei(University of Manchester) Session: INS5: Radio to sub-millimeter technology developments for receiver arrays Displayed during: Poster Session B Summary: At present, space and ground based sub-millimetre systems are based on a single pixel model, utilising a corrugated horn at the front end of the instrument to couple the incident radiation to the optics. While these systems function very well, the natural progression is to extend them to multiple pixels to allow more efficient observations to be made. This becomes critical for space based missions in which the instrument has a finite lifetime.
Such instruments would require arrays of horns, one for each pixel. Corrugated horns are time and cost intensive to produce, which makes them less ideal for arrays containing potentially hundreds of horns, particularly if the technology is to be introduced in a commercial sense (security and medical imaging, for example). The goal therefore, is to produce a feed horn with similar performance to that of a corrugated horn, but with a limited number of corrugations, or ideally none.
We investigate the performance of a Pickett-Potter horn when its design is optimised subject to a number of degrees of freedom, in order to achieve specified levels of performance similar to those of a corrugated horn, under specific headings such as cross polar power, gaussicity and mode content. We also investigate using smooth walled Gaussian profiled horns for this purpose.
Lens antenna system study for future CMB polarisation projects. Author: Fahri Ozturk The University of Manchester, JBCA Co-Authors: B. MAFFEI (1)
G. PISANO (1)
H.T. FUNG (1)
M.W. NG (1)
V. HAYNES (1)
(1) JBCA, School of Physics and Astronomy, The University of Manchester, UK
Session: INS5: Radio to sub-millimeter technology developments for receiver arrays Displayed during: Poster Session B Summary: The next generation of instruments dedicated to the Cosmic Microwave Background Radiation (CMBR) polarisation measurement will require large focal planes including several thousand of pixels. Future lens-based telescope configurations (such as LSPE, SPIDER) might be a strong alternative to the reflector based ones (Planck, WMAP). However, their readiness level is deemed low in term of RF performance knowledge and hence they are being studied in order to understand their systematic effects such as aberrations and cross-polarisation. The work presented here introduces RF simulations using different optical models such as Method of Moments (MOM) and Finite Element Method (FEM). These simulations are also compared to experimental data gathered on a representative lens system (lens and feed-horn) for which the co- and cross-polarisation beam pattern has been measured. The Manchester University Student Telescope (MUST) Author: Monika Obrocka Jodrell Bank Centre for Astrophysics Co-Authors: P. Wilkinson; B. Stappers; MUST Collaboration Session: INS5: Radio to sub-millimeter technology developments for receiver arrays Displayed during: Poster Session B Summary: The first phase of a low cost radio telescope known as the Manchester
University Student Telescope (MUST) is under construction. The design
requirement and science goals, such as pulsar searches and fast radio
transients, are presented in this poster. MUST is a phased array
system that will be able to survey the radio sky due to its
multi-beaming capabilities. The Phase 1 prototype will consist of one
tile of 20 m$^2$ and operate at a centre frequency of 590 MHz with 5 to
10 MHz bandwidth. A New Method to Determine Star Cluster Distances? Author: Anne Buckner Co-Authors: D.Froebrich (University of Kent) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Determining cluster distances is essential to analyse their properties and distribution throughout the Galaxy. In particular it is desirable to have a reliable, purely photometric method for large samples of newly discovered (candidate) clusters (e.g. from 2MASS, UKIDSS-GPS, VISTA-VVV). This would allow us to estimate distances independent of isochrone fits and cluster properties (age and reddening). Here we present our attempt to 'calibrate' such a method, based on a set of about 100 star clusters with known distances.
Our method relies on the photometric decontamination of cluster and field stars, based on the colour and position of a star relative to the cluster, to determine cluster membership probabilities. We then estimate the total number of foreground stars to the cluster (per unit area) based on the colours of low probability cluster members. These are then compared to predictions from the Besancon Galaxy Model by Robin et al. to estimate the cluster distance.
The poster will show our preliminary results on the accuracy of such distance calculations. We will discuss which parameters of the photometric decontamination are required to achieve the best calibration, and if the accuracy depends on e.g. the age of the cluster or its position in the Galaxy.
An analysis of the Herschel data of the star-forming regions Mon R1 and Mon R2 Author: Thomas Rayner Co-Authors: M. Griffin (Cardiff University)
D. Ward-Thompson (Cardiff University)
J. Kirk (Cardiff University)
The SPIRE SAG-3 Team Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Reflection nebulae are usually good indicators of sites of current or recent star formation, as they are formed when the output from a star or stars opens up the parent cloud. In many cases, the clouds will contain yet younger stars and protostars, which are even more valuable to star formation studies. These, however, cannot be observed in visible light, and so must be studied in the infrared part of the spectrum.
Using data from both the Herschel PACS and SPIRE instruments and SCUBA-2 on the JCMT, we study two star-forming regions; the reasonably quiet Mon R1 (part of the Mon OB1 association), and the much denser, brighter Mon R2. We identify the locations and properties of dense clumps in the clouds and characterise these clumps via a mass-size plot, which is used to determine what proportion of them are likely to become stars. We also study the structure of the regions, including that of the filaments in which star formation occurs, and the cores themselves. Direct Observation of the Transition to Coherence and Isothermal Filaments in a Dense Core Author: Jaime E Pineda JBCA, University of Manchester and ESO Co-Authors: A. Goodman (Harvard-Smithsonian CfA), H. Arce (Yale University), P. Caselli (University of Leeds), J. Foster (Boston University), P.C Myers (Harvard-Smithsonian CfA), E. Rosolowsky (University of British Columbia at Okanagan), S. Longmore (ESO), S. Corder (NRAO) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: We present NH3 observations of the B5 region in Perseus obtained with the GBT and EVLA. The GBT map covers a region large enough (11'×14') that it contains the entire dense core observed in previous dust continuum surveys. The dense gas traced by NH3(1,1) covers a much larger area than the dust continuum features found in bolometer observations. The velocity dispersion in the central region of the core is small, presenting subsonic non-thermal motions which are independent of scale. However, it is thanks to the coverage and high sensitivity of the observations that we present the detection, **for the first time**, of the transition between the coherent core and the dense but more turbulent gas surrounding it. This transition is sharp, increasing the velocity dispersion by a factor of 2 in less than 0.04 pc (the 31" beam size at the distance of Perseus, 250 pc).The change in velocity dispersion at the transition is ~3 km s−1 pc−1. The existence of the transition provides a natural definition of dense core: the region with nearly-constant subsonic non-thermal velocity dispersion.
The EVLA observations (27 pointing mosaic) are combined with the GBT map to achieve a 6" beam. This map (~6.8'x8') covers the region of subsonic non-thermal velocity dispersion observed with the GBT. These observations reveal, for the first time, the presence of striking filamentary structure (20" wide or 5,000 AU at the distance of Perseus) in this low-mass star forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. Also, the observed separation between the B5–IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The region observed displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence, and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions.
Finally, we'll discuss the implications of these results on the "core" identification/definition and the importance of the region of subsonic turbulence in the formation process of low-mass stars. Feedback Regulated Star Formation: From Star Clusters to Galaxies Author: Sami Dib Co-Authors: Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: I will summarise results from a model which describes star formation in protocluster clumps of different metallicities. In this model, gravitationally bound cores form uniformly in the clump following a prescribed core formation efficiency per unit time. After a contraction timescale which is equal to a few times their free-fall times, the cores collapse into stars and populate the IMF. Winds from the newly formed OB stars remove gas from the clump until core and star formation are quenched. The power of the radiation driven winds has a strong dependence on metallicity and increases with increasing metallicity. Thus, winds from stars in the high metallicity models lead to a rapid evacuation of the gas from the protocluster clump and to a reduced star formation efficiency, SFE_exp, as compared to their low metallicity counterparts. By combining SFE_exp with the timescales on which gas expulsion occurs, we derive the metallicity dependent star formation rate per unit time in this model as a function of the gas surface density Sigma_g. This is combined with the molecular gas fraction in order to derive the dependence of the surface density of star formation Sigma_SFR on Sigma_g in galactic disks. This feedback regulated model of star formation reproduces very well the observed star formation laws extending from low gas surface densities up to the starburst regime. Furthermore, the results show a dependence of Sigma_SFR on metallicity over the entire range of gas surface densities. Herschel HIFI water observations of low-mass protostellar envelopes in the WISH survey Author: Joseph Mottram Co-Authors: Lars Kristensen (Leiden Observatory), Ewine van Dishoeck (Leiden Observatory) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Herschel observations are revolutionising our understanding of water, a key probe of the temperature, density and kinematics of the warm gas in star formation regions. Recent results from the ``Water in Star-forming regions with Herschel'' (WISH) HIFI Guaranteed Time Key Programme have revealed that embedded YSOs have diverse, rich and complex water line profiles, often containing multiple components tracing different physical processes within a single beam. These different components can be placed in a tentative evolutionary scenario, such that the relative importance of different processes can be explored with time. A specific example is that inverse P-Cygni profiles are much more common in water in deeply embedded low-mass protostars than other chemical species previously studied. 1-D multi-transition radiative transfer modelling of WISH HIFI water observations towards these Class 0 protostars is used to quantify the infall velocities and envelope physical properties in a self-consistent manner. This example will be used to show that water is uniquely sensitive to the dynamics of material around YSOs. The WISH survey is thus providing a valuable legacy, which will shape our understanding of star formation for decades to come. How stars grow massive despite radiation pressure, triggering star-bursts; insights from gravitation Author: Miles F Osmaston Co-Authors: Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Although high-mass stars range up to >100Msun they are evidently shedding up to 90% of their mass at very high rates. This has been attributed to radiation pressure, the only mechanism apparently available. But thermonuclear light-up occurs at well below one solar mass, so why doesn't radiation pressure inhibit accretionary growth to that high mass in the first place? New work on the physics of the gravitation mechanism [1], outlined on this poster, has revealed an expectation that the Newtonian force of any gravitationally-retained assemblage is inescapably accompanied by a radial positive-body-repelling electric field, the Gravity-Electric (G-E field). So this may be responsible for much of the mass loss, primarily of highly ionized material, with radiation pressure playing a smaller rôle.
In that case, accretionary infall of very dust-opaque materials will not be opposed by the G-E field until stellar heat evaporates the dust and ionizes it, very close-in. The Newtonian force will prevail and the star will grow. So the ability to build a high-mass star now depends upon the source cloud's opacity. But the rapid evolution and mass loss of those stars will further increase that opacity - a positive feedback mechanism that could be the trigger for the starburst phenomenon.
[1] Osmaston MF. (2006) GCA 70(18S), A465:- — (2009a) EPSC Abstr. 4, EPSC2009-264:- — (2009b) Geophys.Res. Abstr. 11, EGU2009-12204:- — (2010) In JENAM 2010 (ed. A. Moitinho et al) Abstract Book (Version 2.0) 159-160. — PSS (submitted). Large Scale Infrared Dark Filaments Author: Clare Lenfestey Co-Authors: Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: The galactic plane contains long strings of IRDCs with very high aspect ratios, for example the ‘Nessie’ nebula (Jackson et al. 2010) is 80pc long with an aspect ratio of 150:1. The formation of such filaments is poorly understood; their size implies that it is unlikely that such filaments are formed by turbulence alone, but that cloud-cloud collisions or the interaction of shocks with molecular clouds play an important role. In order to investigate the possible processes behind the formation of such large-scale filaments and the role they play in star formation, a systematic search of the galactic plane has been undertaken. Using the Spitzer IRDC catalogue and minimum spanning trees, 102 candidate filamentary structures have been identified and further investigated using the Herschel HIGAL data to look at their thermal dust emission. This not only provides additional support that the structures detected are indeed coherent, spatially connected filaments, but also allows us to look in greater detail at the fragmentation of the filaments, allowing us to further understand the processes that initiate star formation. The morphologies of infrared dark filaments are varied, ranging from hub-filaments to bubble-like features, but the majority of the structures are long and narrow, similar to Nessie. One of the most intriguing characteristics of the filaments is that the do not appear to be randomly aligned with respect to the galactic plane; they are instead aligned so that they lie parallel to the disc. This could provide evidence that the passage of the spiral arms through the ISM compresses the gas, causing infrared dark filaments to condense and fragment, triggering star formation along the leading edge of the spiral arms. Lonely Cores Observed In Molecular Lines Author: Ciara Quinn Co-Authors: T. Bourke (Harvard-Smithsonian Centre for Astrophysics);
D. Ward-Thompson (Cardiff University) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Isolated star-forming cores are the ideal laboratory for the study of the low-mass star formation process. They have a relatively simple nature and are free from the confusing effects experienced in larger, more crowded molecular clouds and clusters, where multiple star formation events lead to a more complicated picture that is harder to interpret.
The Spitzer legacy program “From Molecular Clouds to Planet-Forming Disks” and its follow-up program “Lonely Cores” mapped more than 100 nearby, isolated cores across a range of evolutionary stages. To study the cores in detail, however, complementary high-resolution spectral-line mapping is needed.
Using the ATNF Mopra Telescope, a 22-m radio telescope, situated in NSW, Australia, we have mapped the 12CO(J=1-0), 13CO(J=1-0) and C18O(J=1-0) emission from ~40 southern cores from the Lonely Cores sample, primarily targeting low density starless cores that may or may not be gravitationally bound, to study possibly the youngest cores .
By conducting an LTE analysis, we have calculated excitation temperatures, optical depths, column densities and masses of the most isolated subset of these cores. By comparing our column density maps with mid-infrared extinction maps, we find that 13CO and C18O are excellent tracers of extinction conditions within these dense cores. Molecular cloud disruption and chemical enrichment of the ISM caused by massive star feedback Author: Katharina Fierlinger Co-Authors: A.M. Burkert (University Observatory Munich); R. Diehl (Max Planck Institute for Extraterrestrial Physics); C. Dobbs (University of Exeter); D.H. Hartmann (Clemson University); M. Krause (Max Planck Institute for Extraterrestrial Physics); E. Ntormousi (University Observatory Munich); R. Voss (Radboud University Nijmegen) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Massive stars shape the interstellar medium and enrich it with freshly-produced heavy elements by means of Wolf-Rayet winds and supernovae explosions. In this work we focus on the feedback efficiency in homogeneous GMCs, turbulent GMCs, as well as irregularly-structured GMCs taken from global disc simulations. Also the enrichment of the ISM with 26Al, a radioactive trace element that decays with an average lifetime of 1 Myr after being ejected from the stars, is studied. For our hydrodynamic simulations we use the RAMSES code and the Geneva grids of stellar evolution models. In all our simulations, a superbubble is formed after break-out from the MC, and then the massive-star outputs rather rapidly disrupt the molecular cloud. The feedback is most disruptive for a homogeneous molecular cloud, whereas the clouds with an irregular density structure have longer lifetimes, since more of the energy from the feedback is channelled into low density surroundings. We find that for structured clouds, the stellar feedback naturally reproduces cavities with asymmetric morphologies, similar to the Orion-Eridanus bubble. Finally we use our calculations to predict the distribution of 26Al, thus providing an important constraint on the timescales for the propagation of stellar winds and supernovae in the ISM. Numerical simulations of a shock interacting with multiple clouds Author: Robertas Aluzas Co-Authors: J.M.Pittard (University of Leeds)
T.W.Hartquist (University of Leeds)
S.A.E.G. Falle (University of Leeds) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: In self-propagating star formation feedback from massive stars induces
further star formation in the galaxy. However, flows and shocks
created by the massive stars can also destroy surrounding clouds.
In order for a shock front to provide positive feedback in star
formation the shock needs to evolve considerably,
perhaps as a result of destroying some "sacrificial" clouds on its way.
I will present the insights gained from numerical simulations where
a shock encounters systems of clouds. As the clouds evolve they affect
the flow and are mixed into it. Clouds further downstream then
evolve differently as they interact with the shock and mass-loaded flow.
I investigate the role of different cloud geometries and number densities
and use a sub-grid turbulence model. Radio continuum observations of low mass young stars driving outflows Author: Rachael E. Ainsworth Dublin Institute for Advanced Studies Co-Authors: A. M. M. Scaife (University of Southampton); T. P. Ray (Dublin Institute for Advanced Studies) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: We present 16 GHz deep radio continuum observations of a sample of classic low-mass young stars driving jets with the Arcminute Microkelvin Imager Large Array (AMI-LA). We compile and examine spectral energy distributions (SEDs) for each source using data from an extensive literature search and calculate both radio and sub-mm spectral indices in two different scenarios: (1) fixing the dust temperature according to evolutionary class; (2) allowing the dust temperature to vary. We use these derived spectral indices to place constraints on the physical mechanisms responsible for the radio emission and find that 80% of the objects in this sample have spectral indices consistent with free-free emission from a partially ionized outflow. We examine correlations between the radio luminosity and bolometric luminosity, envelope mass, and outflow momentum force and investigate the error contributions of different spectral parameters to constraining the radio luminosity of these objects.
Based on AMI Consortium: Ainsworth et al. 2012, in prep Spitzer characterisation of dust in an anomalous emission region: the Perseus Cloud - IRAC and MIPS Author: Christopher Tibbs Co-Authors: N.Flagey (JPL/Caltech); R.Paladini (IPAC/Caltech); M.Compiegne (IPAC/Caltech); S.Shenoy (NASA Ames Research Center); S.Carey (IPAC/Caltech); A.Noriega-Crespo (IPAC/Caltech); C.Dickinson (Jodrell Bank Centre for Astrophysics); Y.Ali-Haimoud (Caltech); S.Casassus (Universidad de Chile); K.Cleary (Caltech); R.Davies (Jodrell Bank Centre for Astrophysics); R.Davis (Jodrell Bank Centre for Astrophysics); C.Hirata (Caltech); R.Watson (Jodrell Bank Centre for Astrophysics) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Anomalous microwave emission is known to exist in the Perseus Molecular Cloud, as recently observed by the Planck satellite, and one of the most promising candidates to explain this excess emission is that of electric dipole radiation from rapidly rotating very small dust grains, commonly referred to as spinning dust. Photometric data observed with the Spitzer Space Telescope have been completely reprocessed and used in conjunction with the dust emission model DUSTEM to characterise the properties of the dust within the cloud. This analysis allowed us to constrain spatial variations in the strength of the interstellar radiation field, the abundances of the PAHs and VSGs relative to the BGs, the column density of hydrogen and the equilibrium dust temperature. These parameter maps were used to investigate the dust properties in regions both with, and without, anomalous emission, and we find that in regions of anomalous emission, the abundances of the PAHs, the strength of the interstellar radiation field and the equilibrium dust temperatures are enhanced, while the column density of hydrogen is decreased. This type of analysis opens a new perspective in the field of anomalous emission studies, and represents a powerful new tool for constraining spinning dust models. Stability of self-gravitating discs under irradiation Author: Ken Rice Institute for Astronomy, University of Edinburgh Co-Authors: P.J. Armitage (University of Colorado, Boulder)
G.R. Mamatsashvili (Observatorio Astronomico di Torino)
G. Lodato (Universita degli Studi di Milano)
C.J. Clarke (Institute of Astronomy, Cambridge) Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Self-gravity becomes competitive as an angular momentum transport process in accretion discs at large radii, where the temperature is low enough that external irradiation likely contributes to the thermal balance. Irradiation is known to weaken the strength of disc self-gravity, and can suppress it entirely if the disc is maintained above the threshold for linear instability. However, its impact on the susceptibility of the disc to fragmentation is less clear. We use two-dimensional numerical simulations to investigate the evolution of self-gravitating discs as a function of the local cooling time and strength of irradiation. Fragmentation requires short cooling times and is found to be a weak function of the level of irradiation. We find that the cooling time boundary increases by approximately a factor of two, as irradiation is increased from zero up to the level where instability is almost quenched. The numerical results imply that irradiation cannot generally avert fragmentation of self-gravitating discs at large radii; if other angular momentum transport sources are weak mass will build up until self-gravity sets in, and fragmentation will ensue. Template fitting of WMAP 7-year data: anomalous dust or flattening synchrotron emission? Author: Michael Peel Jodrell Bank Centre for Astrophysics, University of Manchest Co-Authors: M. W. Peel [1], C. Dickinson [1], R. D. Davies [1], A. J. Banday [2], T. R. Jaffe [2], J. L. Jonas [3]
[1] Jodrell Bank Centre for Astrophysics, University of Manchester
[2] Centre d’Etude Spatiale des Rayonnements, Toulouse
[3] Department of Physics and Electronics, Rhodes University Session: ISM1: Interstellar medium and star formation Displayed during: Poster Session A Summary: Anomalous microwave emission at 20-40GHz has been detected across our Galactic sky. It is highly correlated with thermal dust emission and hence it is thought to be due to spinning dust grains. Alternatively, this emission could be due to synchrotron radiation with a flattening (hard) spectral index. We cross-correlate synchrotron, free-free and thermal dust templates with the WMAP 7-year maps using synchrotron templates at both 408MHz and 2.3GHz to assess the amount of flat synchrotron emission that is present, and the impact that this has on the correlations with the other components. We find that there is only a small amount of flattening visible in the synchrotron spectral indices by 2.3GHz, of around \Delta \approx 0.05, and that the significant level of dust-correlated emission in the lowest WMAP bands is largely unaffected by the choice of synchrotron template, particularly at high latitudes (it decreases by only ~7 per cent when using 2.3 GHz rather than 408 MHz). This agrees with expectation if the bulk of the anomalous emission is generated by spinning dust grains.
(MNRAS, submitted; arXiv:1112.0432) |