Hubble and Galaxy Zoo find that bars and baby galaxies don't mix
Harnessing the power of both the Hubble Space Telescope and the citizen science project Galaxy Zoo, scientists from the University of Portsmouth have found that bar-shaped features in spiral galaxies accelerate the galaxy aging process.
The astronomers found that the fraction of spiral galaxies with bar features has doubled in the last eight billion years – the latter half of the history of the universe. The scientists publish their results, the first from the Galaxy Zoo: Hubble project, in the journal Monthly Notices of the Royal Astronomical Society.
University of Portsmouth postgraduate researcher Tom Melvin led the new study as part of his thesis work. He and the rest of the Galaxy Zoo science team used classifications provided by citizen scientists to select spiral galaxies across the Universe for the study. Light from the furthest galaxies has taken eight billion years to reach us, so we see them as they appeared eight billion years ago or when the cosmos was a little over half its present age. This allows astronomers to study how the characteristics of galaxies change over this time.
Many galaxies with spiral shapes (like the one we live in, the Milky Way) also have central bar-shaped features. These structures are made up of stars and the spiral arms extend from the ends of the bar.
Mr Melvin’s group studied how the fraction of spiral galaxies with bars changed over time. They found that 8 billion years ago only 11% of spirals had bars, but by 2.5 billion years ago this proportion had doubled. In the present day universe two-thirds of galaxies have bars. And the more massive the galaxy, the more likely this is to be the case.
Mr Melvin comments: “This is a really interesting result which has been made possible by the contributions of citizen scientists, who yet again are helping cutting edge astronomical research when they spend time classifying galaxies at Galaxy Zoo.”
The new work also confirms that bars signify maturity for spiral galaxies and may play an important role in switching off the formation of new stars. For some of the most massive spiral galaxies, this happened relatively early in the life of the universe.
Dr Karen Masters, also from Portsmouth University, and Project Scientist for Galaxy Zoo said, “It looks as though bars really are bad for spiral galaxies. As a bar grows in a galaxy, it is less likely to have any new stars being born and the galaxy settles down to a sedate maturity.”
Mr Tom Melvin
Dr Karen Masters
Image and caption
An image is available from http://www.ras.org.uk/images/stories/press/ngc1300.jpg
Caption: A Hubble Space Telescope image of the barred spiral galaxy NGC 1300, located 61 million light years away in the constellation of Eridanus. Credit: HST / NASA / ESA
The new work appears in “Galaxy Zoo: An independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS”, Thomas Melvin (ICG Portsmouth), Karen Masters (ICG Portsmouth), Chris Lintott, Robert C. Nichol, Brooke Simmons, Steven P. Bamford, Kevin R. V. Casteels, Edmond Cheung, Edward M. Edmondson, Lucy Fortson, Kevin Schawinski, Ramin A. Skibba, Arfon M. Smith and Kyle W. Willett, Monthly Notices of the Royal Astronomical Society, in press.
Monthly Notices of the Royal Astronomical Society is published by Oxford University Press. The paper is available from http://mnras.oxfordjournals.org/content/early/2014/01/16/mnras.stt2397
A preprint is available from http://arxiv.org/abs/1401.3334
Notes for editors
The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.
Galaxy Zoo: Hubble was the third phase of the citizen science project Galaxy Zoo (www.galaxyzoo.org). Running from April 2010-August 2012 it collected classifications for more than 80,000 galaxies observed by the Hubble Space Telescope, and more than 85,000 volunteers participated in this phase. Overall Galaxy Zoo (which originally launched in July 2007) has collected classifications from hundreds of thousands of volunteers for more than 1 million galaxies. It continues to be popular with the public, currently hosting new images from the Hubble Space Telescope, the Sloan Digital Sky Survey and the UK Infrared Telescope Digital Sky Survey, and is now part of the Zooniverse; a collection of more than 20 similar projects across all areas of science.