Galaxy environment in the 3D-HST fields. Witnessing the onset of satellite quenching at z ~ 1-2

TL;DR

This study provides a catalog of galaxy environments in the 3D-HST fields, analyzing satellite quenching timescales and mechanisms from redshift 1 to 3, revealing long quenching times driven by gas exhaustion.

Contribution

It introduces a new environmental catalog for galaxies at high redshift and models satellite quenching timescales and phases using mock samples and observational data.

Findings

Satellite quenching timescale is 2-5 Gyr, longer at lower stellar mass and redshift.

Quenching involves a delay phase with star formation similar to centrals, followed by rapid decline.

Satellites retain large gas reservoirs, enabling prolonged star formation before quenching.

Abstract

We make publicly available a catalog of calibrated environmental measures for galaxies in the five 3D-HST/CANDELS deep fields. Leveraging the spectroscopic and grism redshifts from the 3D-HST survey, multi wavelength photometry from CANDELS, and wider field public data for edge corrections, we derive densities in fixed apertures to characterize the environment of galaxies brighter than $JH_{140} < 24$ mag in the redshift range $0.5<z<3.0$. By linking observed galaxies to a mock sample, selected to reproduce the 3D-HST sample selection and redshift accuracy, each 3D-HST galaxy is assigned a probability density function of the host halo mass, and a probability that is a central or a satellite galaxy. The same procedure is applied to a $z=0$ sample selected from SDSS. We compute the fraction of passive central and satellite galaxies as a function of stellar and halo mass, and redshift, and then derive the fraction of galaxies that were quenched by environment specific processes. Using the mock sample, we estimate that the timescale for satellite quenching is $t_{\rm quench} \sim 2-5$ Gyr; longer at lower stellar mass or lower redshift, but remarkably independent of halo mass. This indicates that, in the range of environments commonly found within the 3D-HST sample, satellites are quenched by exhaustion of their gas reservoir in absence of cosmological accretion. We find that the quenching times can be separated into a delay phase during which satellite galaxies behave similarly to centrals at fixed stellar mass, and a phase where the star formation rate drops rapidly ($\sim 0.4-0.6$ Gyr), as shown previously at $z=0$. We conclude that this scenario requires satellite galaxies to retain a large reservoir of multi-phase gas upon accretion, even at high redshift, and that this gas sustains star formation for the long quenching times observed.