The Correlated Formation Histories of Massive Galaxies and Their Dark Matter Halos

TL;DR

This study reveals a correlation between galaxy star formation activity, stellar mass, and large-scale environment, suggesting that halo assembly history influences galaxy evolution over cosmic time.

Contribution

It provides new observational evidence linking galaxy properties to their dark matter halo assembly history across redshifts.

Findings

Star-forming centrals at z=1 have less stellar mass than passive ones at the same halo mass.

Star-forming centrals at z~1 reside in more clustered, denser large-scale environments.

The observed trends imply halo assembly history impacts galaxy star formation and evolution.

Abstract

Using observations in the COSMOS field, we report an intriguing correlation between the star formation activity of massive (~10^{11.4}\msol) central galaxies, their stellar masses, and the large-scale (~10 Mpc) environments of their group-mass (~10^{13.6}\msol) dark matter halos. Probing the redshift range z=[0.2,1.0], our measurements come from two independent sources: an X-ray detected group catalog and constraints on the stellar-to-halo mass relation derived from a combination of clustering and weak lensing statistics. At z=1, we find that the stellar mass in star-forming centrals is a factor of two less than in passive centrals at the same halo mass. This implies that the presence or lack of star formation in group-scale centrals cannot be a stochastic process. By z=0, the offset reverses, probably as a result of the different growth rates of these objects. A similar but weaker trend is observed when dividing the sample by morphology rather than star formation. Remarkably, we find that star-forming centrals at z~1 live in groups that are significantly more clustered on 10 Mpc scales than similar mass groups hosting passive centrals. We discuss this signal in the context of halo assembly and recent simulations, suggesting that star-forming centrals prefer halos with higher angular momentum and/or formation histories with more recent growth; such halos are known to evolve in denser large-scale environments. If confirmed, this would be evidence of an early established link between the assembly history of halos on large scales and the future properties of the galaxies that form inside them.