Satellite content and quenching of star formation in galaxy groups at z~1.8

TL;DR

This study investigates satellite galaxies around massive star-forming galaxies at z~1.8, revealing their significant stellar mass, reduced star formation rates near the halo center, and environmental quenching effects within the hot inner halo.

Contribution

It provides the first statistical analysis of satellite properties at z~1.8, demonstrating environmental quenching and satellite halo characteristics using stacking and modeling techniques.

Findings

Satellites constitute 68% of the central galaxy's stellar mass.

Satellite SFR is 25-35% of the central's SFR.

Star formation in satellites sharply decreases within 100 kpc, likely due to environmental effects.

Abstract

We study the properties of satellites in the environment of massive star-forming galaxies at z~1.8 in the COSMOS field, using a sample of 215 galaxies on the main sequence of star formation with an average mass of 10^11 Msun. At z>1.5, these galaxies typically trace halos of mass >10^13 Msun. We use optical-near-infrared photometry to estimate stellar masses and star formation rates (SFR) of centrals and satellites down to ~6*10^9 Msun. We stack data around 215 central galaxies to statistically detect their satellite halos, finding an average of ~3 galaxies in excess of the background density. We fit the radial profiles of satellites with simple beta-models, and compare their integrated properties to model predictions. We find that the total stellar mass of satellites amounts to 68% of the central galaxy, while SED modeling and far-infrared photometry consistently show their total SFR to be 25-35% of the central's rate. We also see significant variation in the specific SFR of satellites within the halo with, in particular, a sharp decrease at <100 kpc. After considering different potential explanations, we conclude that this is likely an environmental signature of the hot inner halo. This effect can be explained in the first order by a simple free-fall scenario, suggesting that these low-mass environments can shut down star formation in satellites on relatively short timescales of ~0.3 Gyr.