| Description |
We propose to use PACS spectroscopy to observe the OI 63 um, OIII 88and 52 um, and OIV 26 um fine-stucture lines, and PACS/SPIRE photometryto measure the far-IR continuum from 12 IR-bright galaxies in the z = 1 to2 redshift range. These are galaxies from which we have detected emissionin the 158 um CII line using our grating spectrometer, ZEUS, on the CSO.We have found that the most luminous starburst-dominated systems in thisepoch are characterized by kpc-scale moderate intensity star formation,while the AGN-dominated systems host similarly extended, but much moreintense starbursts. The proposed oxygen survey addresses two key questionsstimulated by our CII results: (1) To what extent are luminousstar-forming galaxies at z = 1 to 2 simply scaled-up versions of localstarbursts? (2) Why are the starbursts in AGN-dominated systems so muchmore intense? The oxygen sequence combined with our CII detections willhave powerful diagnostic capabilities, yielding the strength and hardnessof the ambient UV radiation fields, and the density, pressure, and mass ofthe ionized and neutral atomic components. This data will allow us tocharacterize the size and age of the starburst, and the importance of thecentral engine. The ultimate goal is to understand what drives theapparently galaxy-wide starbursts in both star-formation-dominated andAGN-dominated systems, and help identify the connection between starburstsand AGN in the early Universe. This survey is important and unique. Wecover the redshift interval from 1 to 2 near the peak of the starformation per unit co-moving volume in the Universe, and it is within thisredshift interval that the ZEUS and PACS sensitivities are well matched toenable the detection of the CII line together with the oxygen sequencein a wide variety of systems. |
