Cosmic Evolution of Star Formation Enhancement in Close Major-merger Galaxy Pairs Since z = 1
Berta, S.; Magnelli, B.; Lutz, D.; Aussel, H.; Elbaz, D.; Le Floc'h, E.; Pozzi, F.; Riguccini, L.; Béthermin, M.; Wang, L.; Franceschini, A.; Bock, J.; Cooray, A.; Oliver, S. J.; Vaccari, M.; Conley, A.; Scoville, N.; Lu, N.; Schulz, B.; Shupe, D. L.; Xu, C. K.; Zemcov, M.; Vieira, J. D.; Bridge, C.; Marsden, G.
United States, France, Germany, Italy, Canada, United Kingdom, South Africa
Abstract
The infrared (IR) emission of "M * galaxies" (1010.4 <= M star <= 1011.0 M ⊙) 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 spectral energy distribution 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 of which 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 intergalactic medium (IGM) in the dark matter halos hosting these pairs.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.