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Calibrating the HISA temperature: Measuring the temperature of the Riegel-Crutcher cloud

Denes, Helga; McClure-Griffiths, Naomi; Dickey, John; Dawson, Joanne R; Murray, Claire

Description

HI self-absorption (HISA) clouds are clumps of cold neutral hydrogen (H I) visible in front of warm background gas, which makes them ideal places to study the properties of the cold atomic component of the interstellar medium. The Riegel-Crutcher (R-C) cloud is the most striking HISA feature in the Galaxy. It is one of the closest HISA clouds to us and is located in the direction of the Galactic Centre, which provides a bright background. High-resolution interferometric measurements have...[Show more]

dc.contributor.authorDenes, Helga
dc.contributor.authorMcClure-Griffiths, Naomi
dc.contributor.authorDickey, John
dc.contributor.authorDawson, Joanne R
dc.contributor.authorMurray, Claire
dc.date.accessioned2019-10-09T04:25:05Z
dc.date.available2019-10-09T04:25:05Z
dc.identifier.issn0035-8711
dc.identifier.urihttp://hdl.handle.net/1885/173590
dc.description.abstractHI self-absorption (HISA) clouds are clumps of cold neutral hydrogen (H I) visible in front of warm background gas, which makes them ideal places to study the properties of the cold atomic component of the interstellar medium. The Riegel-Crutcher (R-C) cloud is the most striking HISA feature in the Galaxy. It is one of the closest HISA clouds to us and is located in the direction of the Galactic Centre, which provides a bright background. High-resolution interferometric measurements have revealed the filamentary structure of this cloud; however, it is difficult to accurately determine the temperature and the density of the gas without optical depth measurements. In this paper, we present new H I absorption observations with the Australia Telescope Compact Array against 46 continuum sources behind the R-C cloud to directly measure the optical depth of the cloud. We decompose the complex H I absorption spectra into Gaussian components using an automated machine learning algorithm. We find 300 Gaussian components, from which 67 are associated with the R-C cloud (0 < vLSR < 10 km s-1, full width at half maximum < 10 km s-1). Combining the new HI absorption data with HI emission data from previous surveys, we calculate the spin temperature and find it to be between 20 and 80 K. Our measurements uncover a temperature gradient across the cloud with spin temperatures decreasing towards positive Galactic latitudes. We also find three new OH absorption lines associated with the cloud, which support the presence of molecular gas.
dc.description.sponsorshipN.M.-G. acknowledges the support of the Australian Research Council through Future Fellowship FT150100024
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherOxford University Press
dc.rights© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society
dc.sourceMonthly Notices of the Royal Astronomical Society
dc.titleCalibrating the HISA temperature: Measuring the temperature of the Riegel-Crutcher cloud
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume479
dc.date.issued2018
local.identifier.absfor020104 - Galactic Astronomy
local.identifier.ariespublicationu4485658xPUB1333
local.publisher.urlhttp://www.oxfordjournals.org/
local.type.statusPublished Version
local.contributor.affiliationDenes, Helga, College of Science, ANU
local.contributor.affiliationMcClure-Griffiths, Naomi, College of Science, ANU
local.contributor.affiliationDickey, John, University of Tasmania
local.contributor.affiliationDawson, Joanne R, Macquarie University
local.contributor.affiliationMurray, Claire, University of Wisconsin
dc.relationhttp://purl.org/au-research/grants/arc/FT150100024
local.bibliographicCitation.issue2
local.bibliographicCitation.startpage1465
local.bibliographicCitation.lastpage1490
local.identifier.doi10.1093/mnras/sty1384
local.identifier.absseo970102 - Expanding Knowledge in the Physical Sciences
dc.date.updated2019-04-21T08:29:57Z
local.identifier.scopusID2-s2.0-85054723530
dcterms.accessRightsOpen Access
CollectionsANU Research Publications

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