WUNA Lunch Talk:

Kevin Xu

IPAC, Caltech

Close Major-Merger Pairs Since z=1: Evolution of Merger Rate & sSFR Enhancement

September 18

12:10PM, Room 230, NRAO, Edgemont Road


I will present results on the cosmic evolution of galaxy pairs based on studies of two large samples: a local sample (KPAIR, 170 pairs), and a sample of pairs with 0.2 < z < 1 selected in the the COSMOS field (CPAIR, more than 300 pairs). We found a moderately strong cosmic evolution for the pair fraction, with the evolution index of 2.2+-0.2. Major mergers involving star-forming galaxies (i.e., wet and mixed mergers) can account for the formation of both massive ellipticals and red quiescent galaxies (RQGs), and have significant impact on the stellar mass assembly of the most massive galaxies. Results from a new IR study, using data taken from Herschel and Spitzer surveys, showed a significant trend for the enhancement of the specific star formation rate (sSFR) in these pairs to decrease with increasing redshift, probably due to higher gas fractions in higher redshift galaxy disks which in turn may weaken merger induced starbursts.