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Paper: Close Pairs of Galaxies at z≤ 1.5: Mid-Infrared Properties in the Spitzer First Look Survey
Volume: 381, The Second Annual Spitzer Science Center Conference: Infrared Diagnostics of Galaxy Evolution
Page: 363
Authors: Bridge, C.R.; Appleton, P.N.; Conselice, C.J.; Armus, L.; Choi, P.; Fadda, D.T.; Laine, S.; Marleau, F.R.; Helou, G.; Yan, L.
Abstract: By combining the 0.12 square degree Hubble Space Telescope (HST) and Spitzer MIPS 24 μm imaging in the First Look Survey (FLS), we investigate the field-corrected pair fraction and the Mid-Infrared properties of close pairs of galaxies at 0.2 ≤ z≤ 1.5. We identify 134 close galaxy pairs and find that 87 are also detected at 24 μm above the survey’s 100 μJy flux limit. The fraction of 24 μm detected close pairs increases significantly with redshift to 24%±11% at z∼1, in stark contrast to 5%±6% at z∼0.5. Galaxies undetected at 24 μm show a constant pair fraction with redshift of ∼ 2%±6%. Using the 24 μm flux to derive the Far-IR luminosity we find that paired galaxies are responsible for ∼ 25%+5%−4% of the IR luminosity density resulting from star formation at z ∼ 1. We argue that 24 μm detected galaxies are more likely to be in a close pair at all redshifts with a higher fraction in pairs at z ∼ 1, and those in a LIRG/ULIRG phase are significant contributers to the IR and star formation density of the Universe between 0.8 ≤ z ≤ 1.3.
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