ABSTRACT:
The Far-IR spectral regime contains a number of bright atomic ine-structure lines from carbon, nitrogen, and oxygen that often sum to more than 1% of the total luminosity in star-forming galaxies. These lines are sensitive, extinction-free probes of the physical conditions of neutral and moderately ionized gas in galaxies, and of the nature of star formation in these systems. Recent advances in far-IR and sub/millimeter spectroscopic sensitivities are only now allowing these lines to be detected in high redshift sources. I will report on an observational program that uses a PI instrument, ZEUS, at the Caltech Submillimeter Observatory, along with the PACS spectrometer on Herschel, to obtain a first survey of the [CII] 158 um line and other far-IR tracers in a sample of 14 IR-luminous galaxies at z=1-2. Our most important findingis that the star-forming galaxies in our sample with L_FIR=10^{12.5-13} L_sun appear to be forming stars in an extended, low intensity mode, in direct contrast to the intense bursts characterizing local galaxies with the same luminosities.
I will also describe our group's progress in building SuperSpec, an on-chip broadband sub/millimeter-wave spectrometer. SuperSpec utilizes a filterbank of moderate resolution (R ~ 500) channelizers, coupled to lumped element Kinetic Inductance Detectors (KIDs), all integrated onto a single silicon chip. The compact nature of this design, combined with the simplicity of the frequency domain KID readout, will facilitate future large format multi-object spectroscopy. A version of this spectrometer operating in the 1.3mm band and deployed on the proposed 25m CCAT sub/millimeter telescope would be able to rapidly survey the [CII] 158 um line emission from IR-bright galaxies at z=5-9.