A Massive Z = 0.088 Supercluster and Tests of Starburst Galaxy Evolution at the North Ecliptic Pole

Abstract

We present redshifts and luminosities for galaxies in a very deep IRAS field around the north ecliptic pole region (NEPR). The redshift data set consists of 76 sources drawn from co-added and point source filtered IRAS scans of the pole region with 60 microns flux densities bounded between 210 and 50 mJy. This is, therefore, the deepest flux-limited far-infrared sample yet assembled: it extends out to a median redshift of z = 0.080. The sample is strongly clustered in redshift space, with one very strong concentration at z = 0.088, and at least four weaker clusters. The observed portion of the z = 0.088 cluster has a surface density of galaxies more than three times as dense as the Great Wall. This is the deepest far-infrared selected sample yet to become available for tests of starburst galaxy evolution. We have compared the redshift distribution of a subsample to evolutionary models and find the data consistent with either mild (L ∝ [1 + z]<SUP>1-2</SUP>) luminosity evolution, mild (p ∝ [1 + z]<SUP>1-2</SUP>) comoving density evolution, or no evolution. It is difficult, however, to distinguish between true evolution and the effects of large-scale structure in a sample of this size.