Alison L. Coil

AEGIS: Enhancement of Dust-enshrouded Star Formation in Close Galaxy Pairs and Merging Galaxies up to z ~ 1*

Using data from the DEEP2 Galaxy Redshift Survey and HST/ACS imaging in the Extended Groth Strip, we select nearly 100 interacting galaxy systems, including kinematic close pairs and morphologically identified merging galaxies. Spitzer MIPS 24 μm fluxes of these systems reflect the current dusty star formation activity, and at a fixed stellar mass (M*) the median infrared luminosity (LIR) among merging galaxies and close pairs of blue galaxies is twice (1.9 ± 0.4) that of control pairs drawn from isolated blue galaxies. Enhancement declines with galaxy separation, being strongest in close pairs and mergers and weaker in wide pairs compared to the control sample. At ~ 0.9, 7.1% ± 4.3% of massive interacting galaxies (M* > 2 × 1010 M☉) are found to be ULIRGs, compared to 2.6% ± 0.7% in the control sample. The large spread of LIR/M* among interacting galaxies suggests that this enhancement may depend on the merger stage as well as other as yet unidentified factors (e.g., galaxy structure, mass ratio, orbital characteristics, presence of AGN or bar). The contribution of interacting systems to the total IR luminosity density is moderate (36%).