On the Origin and Evolution of the Galaxy Stellar Mass Function

Understand

Here we explore the evolution of galaxy ensembles at early times by writing the in situ stellar mass growth of galaxies purely as a stationary stochastic (e.g., quasi-steady state) process.

• By combining the mathematics of such processes with Newtonian gravity and a mean local star formation efficiency, we show that the stellar mass evolution of galaxy ensembles is directly related to the average acceleration of baryons onto dark matter halos at the onset of star formation, with explicit dependencies on initial local matter densities and halo mass.
• The density term specifically implies more rapid average rates of growth in higher density regions of the universe compared to low density regions, i.e., assembly bias.
• With this framework, using standard cosmological parameters, a mean star formation efficiency derived by other authors, and knowledge of the shape of the cosmological matter power spectrum at small scales, we analytically derive (1) the characteristic stellar masses of galaxies (M*), (2) the power-law low-mass slope (alpha) and normalization (phi*) of the stellar mass function, and (3) the evolution of the stellar mass function in time over 12.5 > z > 2.