The IRAS 1 Jy Survey of Ultraluminous Infrared Galaxies. I. The Sample and Luminosity Function

Abstract

A complete Ñux-limited sample of 118 ultraluminous infrared galaxies (ULIGs) has been identiÐed from the IRAS Faint Source Catalog (FSC). The selection criteria were a 60 km Ñux density greater than 1 Jy in a region of the sky d [ [40¡, o b o [ 30¡. All sources were subsequently reprocessed using co-added IRAS maps in order to obtain the best available Ñux estimates in all four IRAS wavelength bands. The maximum observed infrared luminosity is and the maximum redshift is L ir \ 1012.90 L _ , z \ 0.268. The luminosity function for ULIGs over the decade luminosity range can L ir \ 1012È1013 L _ be approximated by a power law '(L) P L ~2.35[Mpc~3 mag~1]. In the local universe the (z [ 0.1), space density of ULIGs appears to be comparable to or slightly larger than that of optically selected QSOs at comparable bolometric luminosities. A maximum likelihood test suggests strong evolution for our sample ; assuming density evolution proportional to (1 ] z)a we Ðnd a \ 7.6 ^ 3.2. Examination of the two-point correlation function shows a barely signiÐcant level of clustering, m(r) \ 1.6 ^ 1.2, on size scales r D 22 h~1 Mpc.