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

¹ School of Physics, Korea Institute for Advanced Study, Hoegiro 85, Dongdaemun-gu, 130-722 Seoul, Republic of Korea
e-mail: rgobat@kias.re.kr
² Laboratoire AIM-Paris-Saclay, CEA/DSM-CNRS–Université Paris Diderot, Irfu/Service d’Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France
³ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁴ Department of Physics, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany
⁵ Department of Physics, University of Helsinki, Gustaf-Hällströminkatu 2a, 0014 Helsinki, Finland
⁶ Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, UK
⁷ INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁸ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA

Received: 8 April 2015
Accepted: 7 July 2015

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 ~10¹¹M_⊙. At z> 1.5, these galaxies typically trace halos of mass ≳10¹³M_⊙. We use optical-near-infrared photometry to estimate stellar masses and star formation rates (SFR) of centrals and satellites down to ~ 6 × 10⁹M_⊙. 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 β-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 spectral energy distribution 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.