Cosmic Evolution of Star-Formation Enhancement in Close Major-Merger
  Galaxy Pairs Since z = 1
  The infrared (IR) emission of M_* galaxies (10^{10.4} < M_{star} < 10^{11.0}
M_\sun) in galaxy pairs, derived using data obtained in Herschel (PEP/HerMES)
and Spitzer (S-COSMOS) surveys, is compared to that of single disk galaxies in
well matched control samples to study the cosmic evolution of the
star-formation enhancement induced by galaxy-galaxy interaction. Both the mean
IR SED and mean IR luminosity of star-forming galaxies (SFGs) in SFG+SFG (S+S)
pairs in the redshift bin of 0.6 < z < 1 are consistent with no star-formation
enhancement. SFGs in S+S pairs in a lower redshift bin of 0.2 < z < 0.6 show
marginal evidence for a weak star-formation enhancement. Together with the
significant and strong sSFR enhancement shown by SFGs in a local sample of S+S
pairs (obtained using previously published Spitzer observations), our results
reveal a trend for the star-formation enhancement in S+S pairs to decrease with
increasing redshift. Between z=0 and z=1, this decline of interaction-induced
star-formation enhancement occurs in parallel with the dramatic increase (by a
factor of ~10) of the sSFR of single SFGs, both can be explained by the higher
gas fraction in higher z disks. SFGs in mixed pairs (S+E pairs) do not show any
significant star-formation enhancement at any redshift. The difference between
SFGs in S+S pairs and in S+E pairs suggests a modulation of the sSFR by the
inter-galactic medium IGM in the dark matter halos (DMH) hosting these pairs.
