The IRAS 1 Jy survey of ultraluminous infrared galaxies. I. The sample and luminosity function

A complete flux-limited sample of 118 ultraluminous infrared galaxies (ULIGs) has been identified from the IRAS Faint Source Catalog (FSC). The selection criteria were a 60 mu m flux density greater than 1 Jy in a region of the sky delta > -40 degrees, \b\ > 30 degrees. All sources were subsequently reprocessed using coadded IRAS maps in order to obtain the best available flux estimates in all four IRAS wavelength bands. The maximum observed infrared luminosity is L-ir = 10(12.90) L-., and the maximum redshift is z = 0.268. The luminosity function for ULIGs over the decade luminosity range L-ir = 10(12)-10(13) L-. can be approximated by a power law Phi(L) proportional to L-2.35[Mpc(-3) mag(-1)]. In the local universe (z less than or similar to 0.1), the 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)(alpha) we find alpha = 7.6 +/- 3.2. Examination of the two-point correlation function shows a barely significant level of clustering, xi(r)= 1.6 +/- 1.2, on size scales r similar to 22 h(-1) MPc.