We have identified a complete , flux-limited , ( S _ { 160 } > 120 mJy ) , sample of 160 \mu m-selected sources from Spitzer observations of the 1-deg ^ { 2 } ISO Deep Field region in the Lockman Hole .
Ground-based UV , optical and near-infrared ( NIR ) photometry and optical spectroscopy have been used to determine colors , redshifts and masses for the complete sample of 40 galaxies .
Spitzer-IRAC+MIPS photometry , supplemented by ISOPHOT data at 90 \mu m and 170 \mu m , has been used to calculate accurate total infrared luminosities , L _ { IR } ( 8 - 1000 \micron ) , and to determine the IR luminosity function ( LF ) of luminous infrared galaxies ( LIRGs ) .
The maximum observed redshift is z \sim 0.80 and the maximum total infrared luminosity is log ( L _ { IR } / L _ { \sun } ) = 12.74 .
Over the luminosity range log ( L _ { IR } / L _ { \sun } ) = 10 - 12 , the LF for LIRGs in the Lockman Hole Deep Field is similar to that found previously for local sources at similar infrared luminosities .
The mean host galaxy mass , log ( M / M _ { \sun } ) = 10.7 , and dominance of HII-region spectral types , is also similar to what has been found for local LIRGs , suggesting that intense starbursts likely power the bulk of the infrared luminosity for sources in this range of L _ { IR } .
However for the most luminous sources , log ( L _ { IR } / L _ { \sun } ) > 12.0 , we find evidence for strong evolution in the LF \propto ( 1 + z ) ^ { 6 \pm 1 } , assuming pure number density evolution .
These ultraluminous infrared galaxies ( ULIRGs ) have a larger mean host mass , log ( M / M _ { \sun } ) = 11.0 , and exhibit disturbed morphologies consistent with strong-interactions/mergers , and they are also more likely to be characterized by starburst-AGN composite or AGN spectral types .