A New Census of the 0.2 < z < 3.0 Universe. I. The Stellar Mass Function

Abstract

There has been a long-standing factor-of-two tension between the observed star formation rate density and the observed stellar mass buildup after z ∼ 2. Recently we have proposed that sophisticated panchromatic SED models can resolve this tension, as these methods infer systematically higher masses and lower star formation rates than standard approaches. In a series of papers we now extend this analysis and present a complete, self-consistent census of galaxy formation over 0.2 < z < 3 inferred with the Prospector galaxy SED-fitting code. In this work, Paper I, we present the evolution of the galaxy stellar mass function using new mass measurements of ∼10 5 galaxies in the 3D-HST and COSMOS-2015 surveys. We employ a new methodology to infer the mass function from the observed stellar masses: instead of fitting independent mass functions in a series of fixed redshift intervals, we construct a continuity model that directly fits for the redshift evolution of the mass function. This approach ensures a smooth picture of galaxy assembly and makes use of the full, non-Gaussian uncertainty contours in our stellar mass inferences. The resulting mass function has higher number densities at a fixed stellar mass than almost any other measurement in the literature, largely owing to the older stellar ages inferred by Prospector. The stellar mass density is ∼50% higher than previous measurements, with the offset peaking at z ∼ 1. The next two papers in this series will present the new measurements of star-forming main sequence and the cosmic star formation rate density, respectively.

The star formation properties of the observed and simulated AGN Universe: BAT versus EAGLE

“…One scenario that could explain the 0.2-0.4 dex difference in the average stellar masses (and thereby tensions of 0.4 dex in the average sSFRs) found in our study has been postulated in a recent study carried out by Leja et al (2020). They compare stellar mass estimates using parametric SFHs to those estimated using nonparametric SFHS.…”

The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

“…Our derived SMF estimates for four redshift bins (0.15 < z ≤ 0.3, 0.3 < z ≤ 0.5, 0.5 < z ≤ 1.0, and 1.0 < z ≤ 1.5) are presented in Figure 12 alongside a selection of published SMFs from the literature that probe comparable redshifts (Pozzetti et al 2007;Muzzin et al 2013;Leauthaud et al 2016;Wright et al 2018;Leja et al 2020;McLeod & et al 2020, in prep.). We plot error bars for our binned SMF estimates that represent the uncertainty only from Poisson noise and the approximate cosmic variance based on the volume probed for each field.…”

A prediction about the age of thick discs as a function of the stellar mass of the host galaxy

“…. Leja et al (2020) compiled data from galaxies in the redshift range of 0.2 ≤ z ≤ 3.0 and constructed a continuity model to describe φ(M, z) at an arbitrary redshift within the studied range. Their model was built using all the masses and redshifts of the galaxies in their sample simultaneously, without using any sort of binning in either mass or redshift.…”

“…Their model was built using all the masses and redshifts of the galaxies in their sample simultaneously, without using any sort of binning in either mass or redshift. I computed the mass functions with a python code provided by Leja et al (2020) and used the mass functions and Eq. (2) to derive the stellar mass evolution of galaxies with M (z = 0) between 10 9 and 10 11.2 M .…”

“…These redshifts can be transformed into an age, τ, so they can be compared with the observed thick disc ages. For consistency with Leja et al (2020), I assume the WMAP9 cosmology (Hinshaw et al 2013). The resulting age of the youngest stars in thick discs as a function of the host stellar mass is shown in Fig.…”