Galaxy properties in different environments up to z ~ 3 in the GOODS
  NICMOS Survey
  We study the relationship between galaxy colour, stellar mass, and local
galaxy density in a deep near-infrared imaging survey up to a redshift of z~3
using the GOODS NICMOS Survey (GNS). The GNS is a deep near-infrared Hubble
Space Telescope survey imaging a total of 45 square arcminutes of the GOODS
fields, reaching a stellar mass completeness limit of log M* = 9.5 M_sun at
z=3. Using this data we measure galaxy local densities based on galaxy counts
within a fixed aperture, as well as the distance to the 3rd, 5th and 7th
nearest neighbour. We compare the average rest-frame (U-B) colour and fraction
of blue galaxies in different local densities and at different stellar masses.
We find a strong correlation between colour and stellar mass at all redshifts
up to z~3. Massive red galaxies are already in place at z~3 at the expected
location of the red-sequence in the colour-magnitude diagram, although they are
star forming. We do not find a strong correlation between colour and local
density, however, there may be evidence that the highest overdensities are
populated by a higher fraction of blue galaxies than average or underdense
areas. This could indicating that the colour-density relation at high redshift
is reversed with respect to lower redshifts (z<1), where higher densities are
found to have lower blue fractions. Our data suggests that the possible higher
blue fraction at extreme overdensities might be due to a lack of massive red
galaxies at the highest local densities.
