THE GREAT OBSERVATORIES ALL-SKY LIRG SURVEY: COMPARISON OF ULTRAVIOLET AND FAR-INFRARED PROPERTIES

Abstract

The Great Observatories All-sky LIRG Survey (GOALS) consists of a complete\nsample of 202 Luminous Infrared Galaxies (LIRGs) selected from the IRAS Revised\nBright Galaxy Sample (RBGS). The galaxies span the full range of interaction\nstages, from isolated galaxies to interacting pairs to late stage mergers. We\npresent a comparison of the UV and infrared properties of 135 galaxies in GOALS\nobserved by GALEX and Spitzer. For interacting galaxies with separations\ngreater than the resolution of GALEX and Spitzer (2-6"), we assess the UV and\nIR properties of each galaxy individually. The contribution of the FUV to the\nmeasured SFR ranges from 0.2% to 17.9%, with a median of 2.8% and a mean of 4.0\n+/- 0.4%. The specific star formation rate of the GOALS sample is extremely\nhigh, with a median value (3.9*10^{-10} yr^{-1}) that is comparable to the\nhighest specific star formation rates seen in the Spitzer Infrared Nearby\nGalaxies Survey sample. We examine the position of each galaxy on the IR\nexcess-UV slope (IRX-beta) diagram as a function of galaxy properties,\nincluding IR luminosity and interaction stage. The LIRGs on average have\ngreater IR excesses than would be expected based on their UV colors if they\nobeyed the same relations as starbursts with L_IR < 10^{11}L_0 or normal\nlate-type galaxies. The ratio of L_IR to the value one would estimate from the\nIRXg-beta relation published for lower luminosity starburst galaxies ranges\nfrom 0.2 to 68, with a median value of 2.7. A minimum of 19% of the total IR\nluminosity in the RBGS is produced in LIRGs and ULIRGs with red UV colors (beta\n> 0). Among resolved interacting systems, 32% contain one galaxy which\ndominates the IR emission while the companion dominates the UV emission. Only\n21% of the resolved systems contain a single galaxy which dominates both\nwavelengths.\n