Connecting stellar mass and star-formation rate to dark matter halo mass out to z ~ 2

TL;DR

This paper develops an extended halo model linking stellar mass and star-formation rate to dark matter halo mass up to redshift 2, revealing how star formation efficiency and galaxy evolution change over cosmic time.

Contribution

It introduces an empirical extended halo model that connects galaxy properties to halo mass and tracks their evolution using new SFR measurements and simulations.

Findings

Star formation activity decreases from z~2 to 0.

Halos of 10^{11} to 10^{12} solar masses are most efficient at star formation.

Peak SFR density shifts to lower mass halos over time.

Abstract

We have constructed an extended halo model (EHM) which relates the total stellar mass and star-formation rate (SFR) to halo mass (M_h). An empirical relation between the distribution functions of total stellar mass of galaxies and host halo mass, tuned to match the spatial density of galaxies over 0<z<2 and the clustering properties at z~0, is extended to include two different scenarios describing the variation of SFR on M_h. We also present new measurements of the redshift evolution of the average SFR for star-forming galaxies of different stellar mass up to z=2, using data from the Herschel Multi-tiered Extragalactic Survey (HerMES) for infrared-bright galaxies. Combining the EHM with the halo accretion histories from numerical simulations, we trace the stellar mass growth and star-formation history in halos spanning a range of masses. We find that: (1) The intensity of the star-forming activity in halos in the probed mass range has steadily decreased from z~2 to 0; (2) At a given epoch, halos in the mass range between a few times 10^{11} M_Sun and a few times 10^{12} M_Sun are the most efficient at hosting star formation; (3) The peak of SFR density shifts to lower mass halos over time; (4) Galaxies that are forming stars most actively at z~2 evolve into quiescent galaxies in today's group environments, strongly supporting previous claims that the most powerful starbursts at z~2 are progenitors of today's elliptical galaxies.