Gregory H. Rudnick, Kim-Vy Tran, Casey Papovich, Ivelina Momcheva, Christopher Willmer
We study the red sequence in a cluster of galaxies at z=1.62 and follow its evolution over the intervening 9.5 Gyr to the present day. Using deep YJKs imaging with the HAWK-I instrument on the VLT we identify a tight red sequence and construct its rest-frame i-band luminosity function (LF). There is a marked deficit of faint red galaxies in the cluster that causes a turnover in the LF. We compare the red sequence LF to that for clusters at z<0.8 correcting the luminosities for passive evolution. The shape of the cluster red sequence LF does not evolve between z=1.62 and z=0.7 but at z<0.7 the faint population builds up significantly. On the other hand, the inferred total light on the red sequence grows by a factor of ~3 and the bright end of the LF becomes more populated over the period from z=1.62 to 0.7. We construct a simple model for red sequence evolution that grows the red sequence in total luminosity and matches the constant LF shape at z>0.7. In this model the cluster accretes quenched blue galaxies from the field and subsequently allows them to merge. An average of three mergers between z=1.62 and z=0.7 match the observed luminosity functions at the two redshifts. The inferred merger rate is consistent with other studies of this cluster. Our result supports the picture that galaxy merging during the major growth phase of massive clusters is an important process in shaping the red sequence population at all luminosities.
View original:
http://arxiv.org/abs/1203.3541
No comments:
Post a Comment