http://arxiv.org/abs/1312.5317
(Abridged) We probe the merging channel of massive galaxies over the z=0.3-1.3 redshift window by studying close pairs in a sample of 226 galaxies with stellar mass >1E11Msun, from the deep (m<26.5AB, 3 sigma) SHARDS survey. SHARDS provides medium band photometry equivalent to low-resolution optical spectra (R~50), allowing us to obtain extremely accurate photometric redshifts (|Dz|/(1+z)~0.8%, median) and to improve the constraints on the age distribution of the stellar populations. A strong correlation is found between the age difference of central and satellite galaxy and stellar mass ratio, from negligible age differences in major mergers to age differences ~4 Gyr for 1:100 minor mergers. This correlation is inherited from the general mass-age trend, suggesting that no significant bias is found between the satellites of massive centrals and galaxies with similar stellar mass in other environments. The dominant contributor to the growth of massive galaxies corresponds to mass ratios Omega=Msat/Mcen>0.3, followed by a decrease in the fractional mass growth rate linearly proportional to log Omega, at least down to Omega~0.01, suggesting a decreasing role of mergers involving low-mass satellites, especially if dynamical friction timescales are taken into account. A simple model results in an upper limit for the average mass growth rate of massive galaxies of DM/M/Dt~ 0.12+-0.06 per Gyr, over the z<1 range, with a ~60% fractional contribution from (major) mergers with Omega>0.3. The net mass growth from mergers in massive galaxies between z=1 and z=0 is M(z=0)/M(z=1)=1.9 (-0.5) (+0.7). These results suggest that the majority of the stellar mass contributed by satellites does not introduce significantly younger populations, in agreement with the small radial age gradients observed in present-day early-type galaxies.
Fri, 20 Dec 13
41/56
You must be logged in to post a comment.