The Carbon Inventory in a Quiescent, Filamentary Molecular Cloud in G328
  We present spectral line images of [CI] 809 GHz, CO J=1-0 115 GHz and HI 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{\deg} sightline (hereafter G328) in our Galaxy. The [CI] data
comes from the High Elevation Antarctic Terahertz (HEAT) 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
HI datasets come from the Mopra and Parkes/ATCA telescopes, respectively. We
identify a filamentary molecular cloud, ~75 x 5 pc long with mass ~4 x 10E4
Msun and a narrow velocity emission range of just 4 km/s. The morphology and
kinematics of this filament are similar in CO, [CI] and HI, 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
PDR model for a GMC exposed to the average interstellar radiation field. The
[C/CO] abundance ratio averaged through the filament is found to be
approximately unity. The G328 filament is constrained to be cold (Tdust < 20K)
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 be in the process of
formation.
