J/ApJ/880/141ivo://CDS.VizieR/J/ApJ/880/141doi:10.26093/cds/vizier.18800141CDSNguyen H.Dawson J.R.Lee M.-Y.Murray C.E.Stanimirovic S.Heiles C.,Miville-Deschenes M.-A.Petzler A.2021-07-05T07:26:10Z2021-02-08T11:06:57ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frradio-sourcesmolecular-cloudsradio-astronomyWe report Arecibo 21cm absorption-emission observations to characterize the physical properties of neutral hydrogen (HI) in the proximity of five giant molecular clouds (GMCs): Taurus, California, Rosette, Mon OB1, and NGC 2264. Strong HI absorption was detected toward all 79 background-continuum sources in the ~60x20 square degree region. Gaussian decompositions were performed to estimate temperatures, optical depths, and column densities of the cold and warm neutral medium (CNM and WNM). The properties of individual CNM components are similar to those previously observed along random Galactic sightlines and in the vicinity of molecular clouds, suggesting a universality of cold HI properties. The CNM spin temperature (Ts) histogram peaks at ~50K. The turbulent Mach numbers of CNM components vary widely, with a typical value of ~4, indicating that their motions are supersonic. About 60% of the total HI gas is WNM, and nearly 40% of the WNM lies in thermally unstable regime 500-5000K. The observed CNM fraction is higher around GMCs than in diffuse regions, and increases with increasing column density (N_HI_) to a maximum of ~75%. On average, the optically thin approximation (N_HI_^*^) underestimates the total column density by ~21%, but we find large regional differences in the relationship between N_HI_ and the required correction factor, f=N_HI_/N_HI_^*^. We examine two different methods (linear fit of f versus log_10_(N_HI_^*^) and uniform Ts) to correct for opacity effects using emission data from the GALFA-HI survey. We prefer the uniform Ts method because the linear relationship does not produce convincing fits for all subregions.2019ApJ...880..141Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/880/141CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)J/ApJS/97/1 : HST Quasar Absorption Line Key Project. X. (Lockman+ 1995)J/A+A/376/861 : 1420MHz radio continuum survey of southern sky (Reich+, 2001)J/ApJS/145/329 : Millennium Arecibo 21-cm Survey (Heiles+, 2003)J/ApJ/793/132 : Perseus cloud sources Gaussian param. (Stanimirovic+, 2014)J/A+A/580/A112 : THOR. The HI, OH, Recombination Line Survey (Bihr+, 2015)J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)J/ApJS/234/2 : The GALFA-HI survey data release 2 (Peek+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/880/141https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/880/141http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/880/141https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/880/141https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/880/141http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/880/141GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/880/141/table1 (79 sightlines)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/880/141/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/880/141/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/880/141/table1?GETtext/xml+votable180.050000true55.2238757.59038890.0055555555555555566/118 124 272 278 289 326 337 355 392 490 1027 1093 1108 1137 1166 1252 1258 1344 1544 22111 22171 22207 22250 22256 22306 22317 22401 22426 22433 22435 22446 22466 22473 22475 22501 22505 22512 22524 23291 23358 23416 23547 23550 23556 23573 23632 23644 23674 23678 23691 23712 23717 23765 23775 23807 23834 23850 23882 23898 23900 23928 23955 23978 23986 23990 24003 24084 24090 24114 24116 24134 24142 24165 24269 24326 24367 24457 244729.276497240453405e-25 9.276497240453405e-25https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/880/141?format=asciiRadiodefaultJ/ApJ/880/141/table179 sightlinesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNVSSNVSS source identifier (JHHMMSS+DDMMSS)meta.id;meta.maincharNameCommon source identifiermeta.idcharf_NVSS[*] *: indicates excluded from analysismeta.codecharRAJ2000[3/7] Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000[1/36] Degree of Declination (J2000)pos.eq.dec;meta.mainGLON[159.7/214.2] Galactic latitudedegpos.galactic.lonGLAT[-36.3/16.5] Galactic longitudedegpos.galactic.latfloatS1.4[0.57/8.6] NVSS 1.4GHz flux density (VIII/65)Jyphot.flux.density;em.radio.750-1500MHzfloatTSky[3.6/7.6] Sky brightness temperatureKinstr.skyTempfloatSimbadSimbad column added by the CDSmeta.ref.urlcharNEDNED column added by the CDSmeta.ref.urlchar