Journal Article

On the galaxy stellar mass function, the mass–metallicity relation and the implied baryonic mass function

I. K. Baldry, K. Glazebrook and S. P. Driver

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 388, issue 3, pages 945-959
Published in print August 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13348.x
On the galaxy stellar mass function, the mass–metallicity relation and the implied baryonic mass function

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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 ∼108.5M, 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 ∼1011M corresponding to a minimum in feedback effects. The baryonic-infall efficiency may have levelled off at lower masses.

Keywords: galaxies: evolution; galaxies: fundamental parameters; galaxies: haloes; galaxies: luminosity function, mass function

Journal Article.  10251 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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