350 μm Observations of Ultraluminous Infrared Galaxies at Intermediate Redshifts

We present 350micron observations of 36 ultraluminous infrared galaxies(ULIRGs) at intermediate redshifts (0.089 <= z <= 0.926) using theSubmillimeter High Angular Resolution Camera II (SHARC-II) on the CaltechSubmillimeter Observatory (CSO). In total, 28 sources are detected at S/N >= 3,providing the first flux measurements longward of 100micron for a statisticallysignificant sample of ULIRGs in the redshift range of 0.1 < z < 1.0. Combiningour 350micron flux measurements with the existing IRAS 60 and 100micron data,we fit a single-temperature model to the spectral energy distribution (SED),and thereby estimate dust temperatures and far-IR luminosities. Assuming anemissivity index of beta = 1.5, we find a median dust temperature and far-IRluminosity of Td = 42.8+-7.1K and log(Lfir/Lsolar) = 12.2+-0.5, respectively.The far-IR/radio correlation observed in local star-forming galaxies is foundto hold for ULIRGs in the redshift range 0.1 < z < 0.5, suggesting that thedust in these sources is predominantly heated by starbursts. We compare thefar-IR luminosities and dust temperatures derived for dusty galaxy samples atlow and high redshifts with our sample of ULIRGs at intermediate redshift. Ageneral Lfir-Td relation is observed, albeit with significant scatter, due todiffering selection effects and variations in dust mass and grain properties.The relatively high dust temperatures observed for our sample compared to thatof high-z submillimeter-selected starbursts with similar far-IR luminositiessuggest that the dominant star formation in ULIRGs at moderate redshifts takesplace on smaller spatial scales than at higher redshifts.Comment: (24 pages in preprint format, 1 table, 7 figures, accepted for publication in ApJ