On the Reversal of SFR-Density Relation at z=1: Insights from Simulations

Abstract

Recent large surveys have found a reversal of the star formation rate (SFR)-density relation at z=1 from that at z=0 (e.g. Elbaz et al.; Cooper et al.), while the sign of the slope of the color-density relation remains unchanged (e.g. Cucciati et al.; Quadri et al.). We use state-of-the-art adaptive mesh refinement cosmological hydrodynamic simulations of a 21x24x20 (Mpc/h)${}^3$ region centered on a cluster to examine the SFR-density and color-density relations of galaxies at z=0 and z=1. The local environmental density is defined by the dark matter mass in spheres of radius 1 Mpc/h, and we probe two decades of environmental densities. Our simulations produce a large increase of SFR with density at z=1, as in the observations of Elbaz et al. We also find a significant evolution to z=0, where the SFR-density relation is much flatter. The color-density relation in our simulations is consistent from z=1 to z=0, in agreement with observations. We find that the increase in the median SFR with local density at z=1 is due to a growing population of star-forming galaxies in higher-density environments. At z=0 and z=1 both the SFR and cold gas mass are tightly correlated with the galaxy halo mass, and therefore the correlation between median halo mass and local density is an important cause of the SFR-density relation at both redshifts. We also show that the local density on 1 Mpc/h scales affects galaxy SFRs as much as halo mass at z=0. Finally, we find indications that the role of the 1 Mpc/h scale environment reverses from z=0 to z=1: at z=0 high-density environments depress galaxy SFRs, while at z=1 high-density environments tend to increase SFRs.

Accepted to ApJ, 14 pages, 9 figures

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• The DEEP2 Galaxy Redshift Survey: The Relationship Between Galaxy Properties and Environment at z ~ 1
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• The X-Ray Luminosity--Mass Relation for Local Clusters of Galaxies
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• The VIMOS Ultra Deep Survey: The reversal of the star-formation rate $-$ density relation at $2<z<5$
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• ZFIRE: Similar Stellar Growth in H$\alpha$-emitting Cluster and Field Galaxies at z~2
• Probing the Dependence of the Intergalactic Medium on Large Scale Environment Using the Low Redshift Lyman Alpha Forest
• Massive molecular gas reservoir around the central AGN in the CARLA J1103+3449 cluster at z=1.44
• Blueberry and Green Pea galaxies live in low density environments