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dc.contributor.authorIanjamasimanana, Roger
dc.contributor.authorWalter, Fabian
dc.contributor.authorBlok, W. J. G. de
dc.contributor.authorHeald, George H.
dc.contributor.authorBrinks, Elias
dc.date.accessioned2018-07-05T16:03:43Z
dc.date.available2018-07-05T16:03:43Z
dc.date.issued2018-05-14
dc.identifier.citationIanjamasimanana , R , Walter , F , Blok , W J G D , Heald , G H & Brinks , E 2018 , ' Smooth HI Low Column Density Outskirts In Nearby Galaxies ' The Astronomical Journal , vol 155 , no. 6 , 233 . DOI: 10.3847/1538-3881/aabbaa
dc.identifier.issn0004-6256
dc.identifier.otherPURE: 13638827
dc.identifier.otherPURE UUID: 02e0c4bb-82af-4cf7-8504-e58467244651
dc.identifier.otherArXiv: http://arxiv.org/abs/1803.10291v1
dc.identifier.otherScopus: 85048408235
dc.identifier.urihttp://hdl.handle.net/2299/20271
dc.descriptionThis is an author-created, un-copyedited version of an article published in The Astronomical Journal. The Version of Record is available online at https://doi.org/10.3847/1538-3881/aabbaa.
dc.description.abstractThe low column density gas at the outskirts of galaxies as traced by the 21 cm hydrogen line emission (HI) represents the interface between galaxies and the intergalactic medium, i.e., where galaxies are believed to get their supply of gas to fuel future episodes of star formation. Photoionization models predict a break in the radial profiles of HI at a column density of 5x10E+19 cm^-2 due to the lack of self-shielding against extragalactic ionizing photons. To investigate the prevalence of such breaks in galactic disks and to characterize what determines the potential "edge" of the HI disks, we study the azimuthally-averaged HI column density profiles of 17 nearby galaxies from The HI Nearby Galaxy Survey (THINGS) and supplemented in two cases with published Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) data. To detect potential faint HI emission that would otherwise be undetected using conventional moment map analysis, we line up individual profiles to the same reference velocity and average them azimuthally to derive stacked radial profiles. To do so, we use model velocity fields created from a simple extrapolation of the rotation curves to align the profiles in velocity at radii beyond the extent probed with the sensitivity of traditional integrated HI maps. With this method, we improve our sensitivity to outer-disk HI emission by up to an order of magnitude. Except for a few disturbed galaxies, none show evidence for a sudden change in the slope of the HI radial profiles, the alleged signature of ionization by the extragalactic background.en
dc.format.extent22
dc.language.isoeng
dc.relation.ispartofThe Astronomical Journal
dc.rights/dk/atira/pure/core/openaccesspermission/open
dc.subjectgalaxies: evolution
dc.subjectgalaxies: halos
dc.subjectgalaxies: ISM
dc.subjectradio lines: ISM
dc.titleSmooth HI Low Column Density Outskirts In Nearby Galaxiesen
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.contributor.institutionCentre for Astrophysics Research
dc.description.statusPeer reviewed
dc.relation.schoolSchool of Physics, Astronomy and Mathematics
dc.description.versiontypeFinal Accepted Version
dcterms.dateAccepted2018-03-26
rioxxterms.versionAM
rioxxterms.versionofrecordhttps://doi.org/10.3847/1538-3881/aabbaa
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue
herts.rights.accesstypeopenAccess


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