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NAM2011 Presentation Details

Record 145 of 382

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12CO lines and LVG Model: NGC6946

Author: Selcuk Topal

Oxford Physics

Co-Authors: E.Bayet (Oxford Astrophysics), M.Bureau (Oxford Astrophysics)

Session: GAL: Physics of galaxies at high and low redshift (includes Milky Way)

Presentation type: Poster


The understanding of molecular gas properties is essential to better constrain star formation processes in external galaxies. To determine the gas kinetic temperature (Tk), volume density (n(H2 )) and column density (N(CO)) of the molecular gas using non-local thermodynamic equilibrium models, it is necessary to obtain observations of multiple lines of 12CO. We present such a survey in the nearby galaxy NGC 6946, that includes a very high number of supernovae and has a star formation rate 10-15 times higher than our own Galaxy. We focus on two specific positions in spiral arms that covers three prominent star formation regions. We use the Leiden Atomic and Molecular Database for the collision rates and coefficients, the RADEX code for large velocity gradient (LVG) model calculations, and we apply χ2 tests to choose the best models. We present our LVG model results for the two positions using at least four 12CO transitions, and also the radial distribution of molecular gas up to 5.6 kpc from the center using multiple pointings along a radial cut. Both positions include very warm and dense gas.

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