The relationship between star formation rates, local density and stellar
  mass up to z ~ 3 in the GOODS NICMOS Survey
  We investigate the relation between star formation rates and local galaxy
environment for a stellar mass selected galaxy sample in the redshift range 1.5
< z < 3. We use near-infra-red imaging from an extremely deep Hubble Space
Telescope survey, the GOODS-NICMOS Survey (GNS) to measure local galaxy
densities based on the nearest neighbour approach, while star-formation rates
are estimated from rest-frame UV-fluxes. Due to our imaging depth we can
examine galaxies down to a colour-independent stellar mass completeness limit
of log M\ast = 9.5 M\odot at z ~ 3. We find a strong dependence of star
formation activity on galaxy stellar mass over the whole redshift range, which
does not depend on local environment. The average star formation rates are
largely independent of local environment apart from in the highest relative
over-densities. Galaxies in over-densities of a factor of > 5 have on average
lower star formation rates by a factor of 2 - 3, but only up to redshifts of z
~ 2. We do not see any evidence for AGN activity influencing these relations.
We also investigate the influence of the very local environment on
star-formation activity by counting neighbours within 30 kpc radius. This shows
that galaxies with two or more close neighbours have on average significantly
lower star formation rates as well as lower specific star formation rates up to
z ~ 2.5. We suggest that this might be due to star formation quenching induced
by galaxy merging processes.
