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