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Title: The carbon inventory in a quiescent, filamentary molecular cloud in G328

We present spectral line images of [C I] 809 GHz, CO J = 1-0 115 GHz and H I 1.4 GHz line emission, and calculate the corresponding C, CO and H column densities, for a sinuous, quiescent giant molecular cloud about 5 kpc distant along the l = 328° sightline (hereafter G328) in our Galaxy. The [C I] data comes from the High Elevation Antarctic Terahertz telescope, a new facility on the summit of the Antarctic plateau where the precipitable water vapor falls to the lowest values found on the surface of the Earth. The CO and H I data sets come from the Mopra and Parkes/ATCA telescopes, respectively. We identify a filamentary molecular cloud, ∼75 × 5 pc long with mass ∼4 × 10{sup 4} M {sub ☉} and a narrow velocity emission range of just 4 km s{sup –1}. The morphology and kinematics of this filament are similar in CO, [C I], and H I, though in the latter appears as self-absorption. We calculate line fluxes and column densities for the three emitting species, which are broadly consistent with a photodissociation region model for a GMC exposed to the average interstellar radiation field. The [C/CO] abundance ratio averagedmore » through the filament is found to be approximately unity. The G328 filament is constrained to be cold (T {sub Dust} < 20 K) by the lack of far-IR emission, to show no clear signs of star formation, and to only be mildly turbulent from the narrow line width. We suggest that it may represent a GMC shortly after formation, or perhaps still in the process of formation.« less
Authors:
; ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia)
  2. Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
  3. Carl Sagan Center, SETI Institute, 189 Bernado Avenue, Mountain View, CA 94043-5203 (United States)
  4. Astronomy Department, University of Maryland, College Park, MD 20742 (United States)
  5. KOSMA, I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln (Germany)
  6. School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005 (Australia)
Publication Date:
OSTI Identifier:
22351441
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 782; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABUNDANCE; ANTARCTIC REGIONS; APPROXIMATIONS; CARBON MONOXIDE; DENSITY; DISSOCIATION; EMISSION; FILAMENTS; GALAXIES; GHZ RANGE; LINE WIDTHS; MASS; MOLECULES; PHOTOLYSIS; RECREATIONAL AREAS; STARS; SURFACES; TELESCOPES; WATER VAPOR