On the galaxy stellar mass function, the mass–metallicity relation and the implied baryonic mass function |
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Authors: | I. K. Baldry K. Glazebrook S. P. Driver |
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Affiliation: | Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD;Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail 31, P.O. Box 218, Hawthorne, VIC 3122, Australia;SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS |
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Abstract: | A comparison between published field galaxy stellar mass functions (GSMFs) shows that the cosmic stellar mass density is in the range 4–8 per cent of the baryon density (assuming Ωb= 0.045 ). There remain significant sources of uncertainty for the dust correction and underlying stellar mass-to-light ratio even assuming a reasonable universal stellar initial mass function. We determine the z < 0.05 GSMF using the New York University Value-Added Galaxy Catalog sample of 49 968 galaxies derived from the Sloan Digital Sky Survey and various estimates of stellar mass. The GSMF shows clear evidence for a low-mass upturn and is fitted with a double Schechter function that has α2≃−1.6 . At masses below ∼108.5 M⊙ , the GSMF may be significantly incomplete because of missing low-surface-brightness galaxies. One interpretation of the stellar mass–metallicity relation is that it is primarily caused by a lower fraction of available baryons converted to stars in low-mass galaxies. Using this principle, we determine a simple relationship between baryonic mass and stellar mass and present an 'implied baryonic mass function'. This function has a faint-end slope, α2≃−1.9 . Thus, we find evidence that the slope of the low-mass end of the galaxy mass function could plausibly be as steep as the halo mass function. We illustrate the relationship between halo baryonic mass function → galaxy baryonic mass function → GSMF. This demonstrates the requirement for peak galaxy formation efficiency at baryonic masses ∼1011 M⊙ corresponding to a minimum in feedback effects. The baryonic-infall efficiency may have levelled off at lower masses. |
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Keywords: | galaxies: evolution galaxies: fundamental parameters galaxies: haloes galaxies: luminosity function, mass function |
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