2015A&A...581A..56G

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 ∼6x10⁹M_☉. 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 <100kpc. 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 ∼0.3Gyr.