Wide-Field Imaging Spectroscopy in the Submillimeter: SPIFI on AST/RO

Cornell University, Ithaca NY

Investigators

Abstract

This proposal is to map the Milky Way Galactic Center and nearby galaxies in their bright CO, CI, and NII emission lines using the SPIFI (South Pole Fabry-Perot Interferometer) on the AST/RO telescope at the South Pole Station. SPIFI was deployed for the first time on AST/RO during the 2003-04 summer season and is now observing (through winter of 2004) the [NII] and high-J CO lines using the current 5 x 5 pixel array of thermister-sensed (TES) bolometers. Meanwhile, the Cornell group is developing a 16 x 32 pixel array of TES bolometers, which will be installed on SPIFI during the austral summer of 2004-05. Thus, during the 2005 and 2006 winters, SPIFI will be able to image Galactic and extragalactic sources in these spectral lines using the larger format array. The project's objectives are the following: (1) To map the Large Magellanic Cloud in the [CI] 370 microns, CO(7-6), and [NII] lines. The low metalicity environment in this dwarf galaxy may mimic that of protogalaxies, so that investigating the interaction between star formation and the interstellar medium (ISM) in these galaxies is key to understanding the star formation process in the early Universe. (2) Characterize the physical conditions of the ISM in nearby galaxies with the first fully sampled maps in the [CI], CO(7-6), and [NII] 205microns lines. These data are unique -- large-scale spatial and velocity information in transitions that are energetically important -- and will be key to understanding the relationships between density waves, bar potentials, and galaxy-wide star formation. (3) Image the inner 1.5 x 5.0 degrees regions of the Milky Way Galaxy (108,000 spectra/map) in the [CI] 370 microns, CO(7-6) 372 microns, and [NII] 205 microns lines, and smaller regions in the high J CO lines, thereby characterizing the excitation of the molecular, photodissociated, and ionized ISM in the "Central Molecular Zone" (CMZ) and tracing the gas dynamics. Comparing to SPIFI, the "state-of-the-art" heterodyne systems would take ~300 times longer (~1 day of SPIFI observations translates to ~1 year of heterodyne observations) to reach the same sensitivity over the same size maps. The results will be promptly published in scientific journals, and the large maps will be released within a year of data verification. Students (both undergraduate, and graduate), and post-docs are vitally important to the research presented in the proposal. Along the way, they design and develop many pieces of SPIFI's equipment, and learn how to use scientific and engineering software packages, including IDL, Mechanical Desktop, Adobe Photoshop, and Zeemax. Three Cornell graduate students and two post-docs have already worked on SPIFI.