The evolution of the stellar mass versus halo mass relationship

TL;DR

This paper analyzes the evolution of the stellar mass versus halo mass relationship using the Galform model, showing it evolves weakly under standard feedback assumptions and exploring how modifications affect this evolution.

Contribution

It demonstrates that standard semi-analytic models predict weak evolution of the SHM relation and explains the roles of feedback and gas reincorporation in this process.

Findings

Weak evolution of SHM relation from z=0 to z=4 under standard feedback.

Constant gas reincorporation efficiency leads to stable stellar-halo mass ratios.

Modifications to feedback or reincorporation can cause significant evolution of the SHM relation.

Abstract

We present an analysis of the predictions made by the Galform semi-analytic galaxy formation model for the evolution of the relationship between stellar mass and halo mass. We show that for the standard implementations of supernova feedback and gas reincorporation used in semi-analytic models, this relationship is predicted to evolve weakly over the redshift range 0<z<4. Modest evolution in the median stellar mass versus halo mass (SHM) relationship implicitly requires that, at fixed halo mass, the efficiency of stellar mass assembly must be almost constant with cosmic time. We show that in our model, this behaviour can be understood in simple terms as a result of a constant efficiency of gas reincorporation, and an efficiency of SNe feedback that is, on average, constant at fixed halo mass. We present a simple explanation of how feedback from active galactic nuclei (AGN) acts in our model to introduce a break in the SHM relation whose location is predicted to evolve only modestly. Finally, we show that if modifications are introduced into the model such that, for example, the gas reincorporation efficiency is no longer constant, the median SHM relation is predicted to evolve significantly over 0<z<4. Specifically, we consider modifications that allow the model to better reproduce either the evolution of the stellar mass function or the evolution of average star formation rates inferred from observations.