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