J/ApJ/793/132ivo://CDS.VizieR/J/ApJ/793/132doi:10.26093/cds/vizier.17930132CDSStanimirovic S.Z.Murray C.E.Lee M.-Y.Heiles C.Miller J.2017-05-29T08:10:39Z2017-05-12T15:54:45ZCDS support team

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

cds-question@unistra.frmilky-way-galaxymolecular-cloudsinterstellar-mediumradio-sourcesspectroscopyh-i-line-emissionUsing the Arecibo Observatory, we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases, allowing us to estimate spin temperature (T_s_) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual H I clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium (CNM and WNM), respectively) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium H I survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have, on average, a higher total H I column density and the CNM fraction, suggesting an enhanced amount of cold H I relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick H I. Only ~15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with >~85% of Planck's sky coverage. The observed CNM fraction is inversely proportional to the optical depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. (2014ApJ...786...64K). While the CNM fraction is, on average, higher around Perseus relative to a random interstellar field, it is generally low, between 10%-50%. This suggests that extended WNM envelopes around molecular clouds and/or significant mixing of CNM and WNM throughout molecular clouds are present and should be considered in the models of molecule and star formation. Our detailed comparison of H I absorption with CO emission spectra shows that only 3 of the 26 directions are clear candidates for probing the CO-dark gas as they have N(H I)>10^21^/cm2 yet no detectable CO emission.2014ApJ...793..132Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/793/132CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)J/ApJS/145/329 : Millennium Arecibo 21-cm Survey (Heiles+, 2003)J/ApJ/638/293 : 1.1mm sources in the Perseus Molecular Cloud (Enoch+, 2006)J/ApJ/646/1009 : Structures of dust in Perseus molecular cloud (Kirk+, 2006)J/ApJ/668/1042 : Dense cores in Perseus molecular cloud (Kirk+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/793/132https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/793/132http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/793/132https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/793/132https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/793/132http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/793/132GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/793/132/table1 (Source List)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/793/132/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/793/132/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/793/132/table1?GETtext/xml+votable180.050000true29.303541728.86069170.0055555555555555566/375 500 764 839 876 911 928 946 975 1068 1093 1137 1147 1154 1250 1544 1546 1549 2136 2137 2308 2323 2324 2331 24247 243009.276497240453405e-25 9.276497240453405e-25https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/793/132?format=asciiOpticalRadiodefaultJ/ApJ/793/132/table1Source ListSimbadNameSimbad column added by the CDSmeta.idcharIDSource identifiermeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainTsrcNVSS flux density at 1.4GHzJyphot.flux.density;em.radio.750-1500MHzfloatTskySky temperatureKinstr.skyTemp;obs.fieldfloatNote[a] Note on 4C+32.14 (1)meta.notecharJ/ApJ/793/132/table2Gaussian Parameters Associated with All CNM and WNM Components for Each Source from Erratum, 2015, ApJ, 799, 239IDSource identifiermeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTBBrightness temperature (1)Kphys.temperaturefloate_TB? Uncertainty in TBKstat.errorfloatnullableVLSRCentral velocity of fitted Gaussian function (2)km/sphys.veloc;pos.lsrfloate_VLSR? Uncertainty in VLSRkm/sstat.error;phys.veloc;pos.lsrfloatnullableDelVFWHM of fitted Gaussian function (2)km/sspect.line.widthfloate_DelV? Uncertainty in DelVkm/sstat.errorfloatnullabletauPeak optical depth (3)phys.absorption.opticalDepth;stat.maxfloate_tau? Uncertainty in taustat.errorfloatnullableTsSpin temperature (4)Kphys.temperatureinte_Ts? Uncertainty in TsKstat.errorintnullableTkmaxMaximum kinetic temperature (5)Kphys.temperature;stat.maxintNHIH I column density (6)1e+20cm**-2phys.columnDensityfloatForO[0/8] WNM or CNM code (7)meta.notefloat