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

We study the properties of satellites in the environment of massive star-forming galaxies at z similar to 1.8 in the COSMOS field, using a sample of 215 galaxies on the main sequence of star formation with an average mass of similar to 10(11) M-circle dot. At z > 1.5, these galaxies typically trace halos of mass greater than or similar to 10(13) M-circle dot. We use optical-near-infrared photometry to estimate stellar masses and star formation rates (SFR) of centrals and satellites down to similar to 6 x 10(9) M-circle dot. We stack data around 215 central galaxies to statistically detect their satellite halos, finding an average of similar to 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 similar 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 similar to 0.3 Gyr.