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arXiv · 1211.5770

The Far-Infrared, UV and Molecular Gas Relation in Galaxies up to z=2.5

R. Nordon·D. Lutz·A. Saintonge·S. Berta·S. Wuyts·N. M. Forster Schreiber·R. Genzel·B. Magnelli·A. Poglitsch·P. Popesso·D. Rosario·E. Sturm·L. J. Tacconi
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Abstract

We use the infrared excess (IRX) FIR/UV luminosity ratio to study the relation between the effective UV attenuation (A_IRX) and the UV spectral slope (beta) in a sample of 450 1 9.3. Thus, we are able to study galaxies on and even below the main SFR-stellar mass relation (main sequence). We find that main sequence galaxies form a tight sequence in the IRX--beta plane, which has a flatter slope than commonly used relations. This slope favors a SMC-like UV extinction curve, though the interpretation is model dependent. The scatter in the IRX-beta plane, correlates with the position of the galaxies in the SFR-M plane. Using a smaller sample of galaxies with CO gas masses, we study the relation between the UV attenuation and the molecular gas content. We find a very tight relation between the scatter in the IRX-beta plane and the specific attenuation (S_A), a quantity that represents the attenuation contributed by the molecular gas mass per young star. S_A is sensitive to both the geometrical arrangement of stars and dust, and to the compactness of the star forming regions. We use this empirical relation to derive a method for estimating molecular gas masses using only widely available integrated rest-frame UV and FIR photometry. The method produces gas masses with an accuracy between 0.12-0.16 dex in samples of normal galaxies between z~0 and z~1.5. Major mergers and sub-millimeter galaxies follow a different S_A relation.

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R. Nordon, D. Lutz, A. Saintonge, S. Berta, S. Wuyts, N. M. Forster Schreiber, R. Genzel, B. Magnelli, A. Poglitsch, P. Popesso, D. Rosario, E. Sturm, L. J. Tacconi. 2012-11-25. The Far-Infrared, UV and Molecular Gas Relation in Galaxies up to z=2.5. https://doi.org/10.1088/0004-637x%2F762%2F2%2F125

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