Publications of the Astronomical Society of Australia

Research Article

The Mopra Southern Galactic Plane CO Survey

Michael G. Burtona1 c1, C. Braidinga1, C. Gluecka2, P. Goldsmitha3, J. Hawkesa4, D. J. Hollenbacha5, C. Kulesaa6, C. L. Martina7, J. L. Pinedaa3, G. Rowella4, R. Simona2, A. A. Starka8, J. Stutzkia2, N. J. H. Tothilla1a9, J. S. Urquharta10, C. Walkera6, A. J. Walsha11 and M. Wolfirea12

a1 School of Physics, University of New South Wales, Sydney, NSW 2052, Australia

a2 KOSMA, I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

a3 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA

a4 School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005, Australia

a5 Carl Sagan Center, SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043-5203, USA

a6 Steward Observatory, The University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA

a7 Department of Physics and Astronomy, Oberlin College, 110 N. Professor St., Oberlin, OH 44074, USA

a8 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

a9 School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia

a10 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

a11 International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA, Australia

a12 Astronomy Department, University of Maryland, College Park, MD 20742, USA

Abstract

We present the first results from a new carbon monoxide (CO) survey of the southern Galactic plane being conducted with the Mopra radio telescope in Australia. The 12CO, 13CO, and C18O J = 1–0 lines are being mapped over the portion of the fourth quadrant of the Galaxy, at 35 arcsec spatial and 0.1 km s−1 spectral resolution. The survey is being undertaken with two principal science objectives: (i) to determine where and how molecular clouds are forming in the Galaxy and (ii) to probe the connection between molecular clouds and the ‘missing’ gas inferred from gamma-ray observations. We describe the motivation for the survey, the instrumentation and observing techniques being applied, and the data reduction and analysis methodology. In this paper, we present the data from the first degree surveyed, . We compare the data to the previous CO survey of this region and present metrics quantifying the performance being achieved; the rms sensitivity per 0.1 km s−1 velocity channel is ~1.5 K for and ~0.7 K for the other lines. We also present some results from the region surveyed, including line fluxes, column densities, molecular masses, line ratios, and optical depths. We also examine how these quantities vary as a function of distance from the Sun when averaged over the 1 square degree survey area. Approximately 2 × 106M of molecular gas is found along the G323 sightline, with an average H2 number density of cm−3 within the Solar circle. The CO data cubes will be made publicly available as they are published.

(Received May 15 2013)

(Accepted July 03 2013)

(Online publication August 14 2013)

Keywords:

  • Galaxy: kinematics and dynamics – Galaxy: structure – ISM: clouds – ISM: molecules – radio lines: ISM – surveys

Correspondence

c1 Email: m.burton@unsw.edu.au

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