GAMA/G10-COSMOS/3D-HST: Evolution of the galaxy stellar mass function over 12.5Gyrs

TL;DR

This study analyzes galaxy stellar-mass function evolution over 12.5 billion years using combined datasets, revealing remarkable stability in shape parameters and a simple high-mass buildup over cosmic time.

Contribution

It demonstrates that the galaxy stellar-mass function's shape parameters have remained stable over cosmic time, challenging previous notions of significant evolution.

Findings

Shape parameters are stable over time.

High-mass component growth explains stellar-mass function evolution.

Stellar mass density increases via constant high-mass source growth.

Abstract

Using a combined and consistently analysed GAMA, G10-COSMOS, and 3D-HST dataset we explore the evolution of the galaxy stellar-mass function over lookback times $t_{\rm L} \in \left[0.2,12.5\right] {\rm h^{-1}_{70} Gyr}$. We use a series of volume limited samples to fit Schechter functions in bins of $\sim\!$constant lookback time and explore the evolution of the best-fit parameters in both single and two-component cases. In all cases, we employ a fitting procedure that is robust to the effects of Eddington bias and sample variance. Surprisingly, when fitting a two-component Schechter function, we find essentially no evidence of temporal evolution in $M_\star$, the two $\alpha$ slope parameters, or the normalisation of the low-mass component. Instead, our fits suggest that the various shape parameters have been exceptionally stable over cosmic time, as has the normalisation of the low-mass component, and that the evolution of the stellar-mass function is well described by a simple build up of the high-mass component over time. When fitting a single component Schechter function, there is an observed evolution in both $M_\star$ and $\alpha$, however this is interpreted as being an artefact. Finally, we find that the evolution of the stellar-mass function, and the observed stellar mass density, can be well described by a simple model of constant growth in the high-mass source density over the last $11 {\rm h^{-1}_{70} Gyr}$.