Probing the Interstellar Medium Conditions in High Redshift Starburst Galaxies

Farinfrared and submillimeter emission lines trace the massive gas reservoirs which fuel the increased star formation seen at high redshift. While CII emission at 158 microns is the dominant cooling line in galaxies and directly traces the conditions in the interstellar medium, only a handful of studies have managed to detect CII at high redshift. We propose to double the number of published high redshift CII detections by observing 4 ultraluminous infrared galaxies at z1.22.5 with the SPIRE FTS. Our sample is unique in that it already has exquisite measurements of midIR spectral features and CO emission ensuring that we are observing gasrich, starburstdominated systems. Combining the CII measurements with line luminosities from CO and midIR spectroscopy we will complete a full diagnosis of the interstellar medium in these intensely star forming systems constraining the gas density, and the strength and source of the UV radiation field. This program is an excellent way to push the limits and showcase the capabilities of the SPIRE/FTS. We request a modest allocation of 21.7 hours (5.5 hours per source) to complete this detailed study of the astrophysical conditions in high redshift ultraluminous infrared galaxies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]