Stellar mass functions of galaxies, disks and spheroids at z~0.1

TL;DR

This study analyzes the stellar mass functions of galaxies and their components at z~0.1, revealing the distribution, contributions, and mass ratios of spheroids and disks in a large SDSS sample.

Contribution

It provides detailed measurements of galaxy, spheroid, and disk stellar mass functions and their relative contributions at low redshift, with new insights into the mass-dependent dominance of galaxy components.

Findings

Galaxy SMF well fitted by a Schechter function with specific parameters.

Identified a crossover stellar mass where spheroid and disk contributions are equal.

Disk dominance at low masses decreases with increasing stellar mass, favoring spheroids at higher masses.

Abstract

We present the stellar mass functions (SMF) and mass densities of galaxies, and their spheroid and disk components in the local (z~0.1) universe over the range 8.9 <= log(M/M_solar) <= 12 from spheroid+disk decompositions and corresponding stellar masses of a sample of over 600,000 galaxies in the SDSS-DR7 spectroscopic sample. The galaxy SMF is well represented by a single Schechter function (M* = 11.116+/-0.011, alpha = -1.145+/-0.008), though with a hint of a steeper faint end slope. The corresponding stellar mass densities are (2.670+/-0.110), (1.687+/-0.063) and (0.910+/-0.029)x10^8 M_solar Mpc^-3 for galaxies, spheroids and disks respectively. We identify a crossover stellar mass of log(M/M_solar) = 10.3+/-0.030 at which the spheroid and disk SMFs are equal. Relative contributions of four distinct spheroid/disk dominated sub-populations to the overall galaxy SMF are also presented. The mean disk-to-spheroid stellar mass ratio shows a five fold disk dominance at the low mass end, decreasing monotonically with a corresponding increase in the spheroidal fraction till the two are equal at a galaxy stellar mass, log(M/M_solar)=10.479+/-0.013, the dominance of spheroids then grows with increasing stellar mass. The relative numbers of composite disk and spheroid dominated galaxies show peaks in their distributions, perhaps indicative of a preferred galaxy mass. Our characterization of the low redshift galaxy population provides stringent constraints for numerical simulations to reproduce.