2006ApJ...650...12K

We use deep multiband optical and near-infrared data for four general fields, GOODS-South, HDF-North/South, and IRAC UDF in GOODS-North to investigate the evolution of the observed rest-frame U-V color of field galaxies as a function of the stellar mass evaluated by fitting the galaxy spectral models to the observed broadband SEDs. In these four fields, the U-V color distributions of the galaxies at each mass and redshift interval are very similar. We found that at 0.3<z<2.7, more massive galaxies always tend to have a redder U-V color. High- and low-mass galaxies exhibit quite different color evolutions. As seen in our previous study in HDF-N, the color distribution of low-mass (M_*≲3x10⁹ M_☉) galaxies becomes significantly bluer with an increase in the redshift. This evolution of the average color can be explained by a constant star formation rate model with z_form∼4. On the other hand, the average color of high-mass galaxies (M_*≳3x10¹⁰ M_☉) evolves more strongly at high redshifts. Such mass-dependent color distribution and its evolution indicate that galaxies with a larger stellar mass appear to have shorter star formation timescales, and on average they form the larger fraction of their stars in the earlier epoch.