Galaxy properties in different environments up to z ~ 3 in the GOODS NICMOS Survey

TL;DR

This study investigates how galaxy colour, stellar mass, and local environment relate up to redshift z~3, revealing early formation of massive red galaxies and potential reversal of the colour-density relation at high redshift.

Contribution

It provides the first detailed analysis of galaxy properties and their environmental dependence up to z~3 using deep near-infrared imaging from the GOODS NICMOS Survey.

Findings

Massive red galaxies are present at z~3, aligning with the red sequence.

No strong correlation between galaxy colour and local density at high redshift.

Possible reversal of the colour-density relation at z~3, with higher blue fractions in overdense regions.

Abstract

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.