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  5.     <title>UTas ePrints - Fitting Together the H i Absorption and Emission in the Southern Galactic Plane Survey</title>
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  32. <meta content="In this paper we study 21 cm absorption spectra and the corresponding emission spectra toward bright continuum sources in the test region (326deg<l<333deg) of the Southern Galactic Plane Survey. This survey combines the high resolution of the Australia Telescope Compact Array with the full brightness temperature information of the Parkes single-dish telescope. In particular, we focus on the abundance and temperature of the cool atomic clouds in the inner Galaxy. The resulting mean opacity of the H i, <kappa>, is measured as a function of Galactic radius; it increases going in from the solar circle, to a peak in the molecular ring of about 4 times its local value. This suggests that the cool phase is more abundant there, and colder, than it is locally. The distribution of cool-phase temperatures is derived in three different ways. The naive, &quot;spin temperature&quot; technique overestimates the cloud temperatures, as expected. Using two alternative approaches, we get good agreement on a histogram of the cloud temperatures, Tcool, corrected for blending with warm-phase gas. The median temperature is about 65 K, but there is a long tail reaching down to temperatures below 20 K. Clouds with temperatures below 40 K are common though not as common as warmer clouds (40-100 K). Using these results, we discuss two related quantities, the peak brightness temperature seen in emission surveys and the incidence of clouds seen in H i self-absorption. Both phenomena match what would be expected based on our measurements of <kappa> and Tcool." name="eprints.abstract" />
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  220.     <h1 class="ep_tm_pagetitle">Fitting Together the H i Absorption and Emission in the Southern Galactic Plane Survey</h1>
  221.     <p style="margin-bottom: 1em" class="not_ep_block"><span class="person_name">Dickey, John M.</span> and <span class="person_name">McClure-Griffiths, N.M.</span> and <span class="person_name">Gaensler, B.M.</span> and <span class="person_name">Green, A.J.</span> (2003) <xhtml:em>Fitting Together the H i Absorption and Emission in the Southern Galactic Plane Survey.</xhtml:em> Astrophysical Journal, 585 (1). pp. 801-822.</p><p style="margin-bottom: 1em" class="not_ep_block"></p><table style="margin-bottom: 1em" class="not_ep_block"><tr><td valign="top" style="text-align:center"><a onmouseover="EPJS_ShowPreview( event, 'doc_preview_2632' );" href="http://eprints.utas.edu.au/2092/1/56608.web.pdf" onmouseout="EPJS_HidePreview( event, 'doc_preview_2632' );"><img alt="[img]" src="http://eprints.utas.edu.au/style/images/fileicons/application_pdf.png" class="ep_doc_icon" border="0" /></a><div class="ep_preview" id="doc_preview_2632"><table><tr><td><img alt="" src="http://eprints.utas.edu.au/2092/thumbnails/1/preview.png" class="ep_preview_image" border="0" /><div class="ep_preview_title">Preview</div></td></tr></table></div></td><td valign="top"><a href="http://eprints.utas.edu.au/2092/1/56608.web.pdf"><span class="ep_document_citation">PDF</span></a> - Requires a PDF viewer<br />911Kb</td></tr></table><p style="margin-bottom: 1em" class="not_ep_block">Official URL: <a href="http://dx.doi.org/10.1086/346081">http://dx.doi.org/10.1086/346081</a></p><div class="not_ep_block"><h2>Abstract</h2><p style="padding-bottom: 16px; text-align: left; margin: 1em auto 0em auto">In this paper we study 21 cm absorption spectra and the corresponding emission spectra toward bright continuum sources in the test region (326deg&lt;l&lt;333deg) of the Southern Galactic Plane Survey. This survey combines the high resolution of the Australia Telescope Compact Array with the full brightness temperature information of the Parkes single-dish telescope. In particular, we focus on the abundance and temperature of the cool atomic clouds in the inner Galaxy. The resulting mean opacity of the H i, &lt;kappa&gt;, is measured as a function of Galactic radius; it increases going in from the solar circle, to a peak in the molecular ring of about 4 times its local value. This suggests that the cool phase is more abundant there, and colder, than it is locally. The distribution of cool-phase temperatures is derived in three different ways. The naive, "spin temperature" technique overestimates the cloud temperatures, as expected. Using two alternative approaches, we get good agreement on a histogram of the cloud temperatures, Tcool, corrected for blending with warm-phase gas. The median temperature is about 65 K, but there is a long tail reaching down to temperatures below 20 K. Clouds with temperatures below 40 K are common though not as common as warmer clouds (40-100 K). Using these results, we discuss two related quantities, the peak brightness temperature seen in emission surveys and the incidence of clouds seen in H i self-absorption. Both phenomena match what would be expected based on our measurements of &lt;kappa&gt; and Tcool.</p></div><table style="margin-bottom: 1em" cellpadding="3" class="not_ep_block" border="0"><tr><th valign="top" class="ep_row">Item Type:</th><td valign="top" class="ep_row">Article</td></tr><tr><th valign="top" class="ep_row">Additional Information:</th><td valign="top" class="ep_row">Copyright 2003, The American Astronomical Society.</td></tr><tr><th valign="top" class="ep_row">Keywords:</th><td valign="top" class="ep_row">atoms: clouds: structure: radio lines&#13;
  222. </td></tr><tr><th valign="top" class="ep_row">Subjects:</th><td valign="top" class="ep_row"><a href="http://eprints.utas.edu.au/view/subjects/240101.html">240000 Physical Sciences &gt; 240100 Astronomical Sciences &gt; 240101 Astronomy and Astrophysics</a></td></tr><tr><th valign="top" class="ep_row">ID Code:</th><td valign="top" class="ep_row">2092</td></tr><tr><th valign="top" class="ep_row">Deposited By:</th><td valign="top" class="ep_row"><span class="ep_name_citation"><span class="person_name">Prof. John M. Dickey</span></span></td></tr><tr><th valign="top" class="ep_row">Deposited On:</th><td valign="top" class="ep_row">11 Oct 2007 16:34</td></tr><tr><th valign="top" class="ep_row">Last Modified:</th><td valign="top" class="ep_row">09 Jan 2008 02:30</td></tr><tr><th valign="top" class="ep_row">ePrint Statistics:</th><td valign="top" class="ep_row"><a target="ePrintStats" href="/es/index.php?action=show_detail_eprint;id=2092;">View statistics for this ePrint</a></td></tr></table><p align="right">Repository Staff Only: <a href="http://eprints.utas.edu.au/cgi/users/home?screen=EPrint::View&amp;eprintid=2092">item control page</a></p>
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