GASS: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release

📝 Abstract

The Parkes Galactic All-Sky Survey (GASS) is a survey of Galactic atomic hydrogen (HI) emission in the Southern sky covering declinations $\delta \leq 1^{\circ}$ using the Parkes Radio Telescope. The survey covers $2\pi$ steradians with an effective angular resolution of ~16’, at a velocity resolution of 1.0 km/s, and with an rms brightness temperature noise of 57 mK. GASS is the most sensitive, highest angular resolution survey of Galactic HI emission ever made in the Southern sky. In this paper we outline the survey goals, describe the observations and data analysis, and present the first-stage data release. The data product is a single cube at full resolution, not corrected for stray radiation. Spectra from the survey and other data products are publicly available online.

💡 Analysis

The Parkes Galactic All-Sky Survey (GASS) is a survey of Galactic atomic hydrogen (HI) emission in the Southern sky covering declinations $\delta \leq 1^{\circ}$ using the Parkes Radio Telescope. The survey covers $2\pi$ steradians with an effective angular resolution of ~16’, at a velocity resolution of 1.0 km/s, and with an rms brightness temperature noise of 57 mK. GASS is the most sensitive, highest angular resolution survey of Galactic HI emission ever made in the Southern sky. In this paper we outline the survey goals, describe the observations and data analysis, and present the first-stage data release. The data product is a single cube at full resolution, not corrected for stray radiation. Spectra from the survey and other data products are publicly available online.

📄 Content

arXiv:0901.1159v1 [astro-ph.GA] 9 Jan 2009 To Appear in ApJS GASS: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release N. M. McClure-Griffiths,1 D. J. Pisano,2,3 M. R. Calabretta,1 H. Alyson Ford,1,4 Felix J. Lockman,2 L. Staveley-Smith,5 P. M. W. Kalberla,6 J. Bailin,7 L. Dedes,6 S. Janowiecki,2,8 B. K. Gibson,9 T. Murphy,10,11 H. Nakanishi,12 K. Newton-McGee1,10 ABSTRACT The Parkes Galactic All-Sky Survey (GASS) is a survey of Galactic atomic hydrogen (H i) emission in the Southern sky covering declinations δ ≤1◦using the Parkes Radio Telescope. The survey covers 2π steradians with an effective angular resolution of ∼16′, at a velocity resolution of 1.0 km s−1, and with an rms brightness temperature noise of 57 mK. GASS is the most sensitive, highest angular resolution survey of Galactic H i emission ever made in the Southern sky. In this paper we outline the survey goals, describe the observations and data analysis, and present the first-stage data release. The data product is a single cube at full resolution, not corrected for stray radiation. Spectra from the survey and other data products are publicly available online. 1Australia Telescope National Facility, CSIRO, Marsfield NSW 2122, Australia; naomi.mcclure-griffiths@csiro.au, mark.calabretta@csiro.au 2National Radio Astronomy Observatory, Green Bank, WV 24944; dpisano@nrao.edu, jlockman@nrao.edu 3present address: Department of Physics, West Virginia University, Morgantown, WV 26506 4Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn VIC 3122, Aus- tralia; alyson@astro.swin.edu.au 5School of Physics, University of Western Australia, Crawley WA 6009, Australia; lister.staveley-smith@uwa.edu 6Argelander-Institut f¨ur Astronomie, Universit¨at Bonn, 53121 Bonn, Germany; pkalberla@astro.uni-bonn.de, ldedes@astro.uni-bonn.de 7Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; bail- inj@mcmaster.ca 8Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106; present address: Department of Astronomy, Indiana University Bloomington, IN 47405; sjanowie@indiana.edu 9Centre for Astrophysics, University of Central Lancashire, Preston, PR1 2HE, UK; bkgibson@uclan.ac.uk 10School of Physics, The University of Sydney, NSW 2006, Australia; tara@physics.usyd.edu.au 11School of Information Technologies, The University of Sydney, NSW 2006, Australia 12Faculty of Science, Kagoshima University, Kagoshima 890-0068, Japan; hnakanis@sci.kagoshima-u.ac.jp – 2 – Subject headings: surveys — ISM: general — radio lines: ISM — galaxies: interactions — Galaxy: structure — Magellanic Clouds 1. Introduction Atomic hydrogen (H i) is a ubiquitous component of disk galaxies. Most readily traced by the λ = 21 cm spectral line, H i from the Milky Way is observed in all directions of the sky. It is possible to trace Galactic H i emission to the far side of the Milky Way, probing Galac- tic and interstellar processes in regions of the Galaxy that are inaccessible at many other wave- lengths. As the dominant component of the interstellar medium (ISM) by number, H i allows us to trace a wide variety of Galactic processes including the impact of massive stars on the ISM (e.g., Heiles 1984; McClure-Griffiths et al. 2002); the interaction of the Galactic disk and halo (e.g., McClure-Griffiths et al. 2006; Lockman et al. 2008); the ISM life-cycle; and the formation of cold clouds (e.g., Gibson et al. 2000; Kavars et al. 2005). Since the discovery of the λ = 21 cm spectral line in 1951 by Ewen & Purcell (1951), it has been used repeatedly, and with continuous refine- ments, to explore the rotation curve and map the global structure of the Galaxy (e.g., Kerr 1962; Henderson et al. 1982; Levine et al. 2006; McClure-Griffiths & Dickey 2007). Not long after the discovery of the H i spectral line, H i emission was found at velocities in excess of |VLSR| ≳100 km s−1 that could not be explained by Galactic rotation (Muller et al. 1963; Smith 1963). These high velocity clouds (HVCs) are now known to cover a significant fraction of the sky (Wakker & van Woerden 1997). HVCs are observed at both positive and negative LSR velocities with magnitudes up to |VLSR| ≲500 km s−1. There have been extensive searches for high velocity gas (see Wakker & van Woerden 1997 for a review, or recent surveys by Putman et al. 2002 and Lockman et al. 2002b). It now seems certain that HVCs represent a variety of phenomena. Some HVCs may be related to a Galactic fountain (e.g., Bregman 1980); some are tidal debris, such as those connected to the Magellanic Stream (e.g., Putman et al. 2003) or other satellites (e.g., Lockman 2003); some may be infalling intergalactic gas (e.g., Complex C; Wakker et al. 1999; Tripp et al. 2003; Lockman et al. 2008)l; and some may be associated with gas condensing from a massive, hot halo (Maller & Bullock 2004; Sommer-Larsen 2006). Studies of the structure and distribution of high

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