J/A+A/651/A59ivo://CDS.VizieR/J/A+A/651/A59doi:10.26093/cds/vizier.36510059CDSLanger W.D.Pineda J.L.Goldsmith P.F.Chambers E.T.Riquelme D.,Anderson L.D.Luisi M.Justen MBuchbender C.2021-10-25T10:11:48Z2021-07-13T08:24:10ZCDS support team

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

cds-question@unistra.frinterstellar-mediumspectroscopyIonized interstellar gas is an important component of the interstellar medium and its lifecycle. The recent evidence for a widely distributed highly ionized warm interstellar gas with a density intermediate between the warm ionized medium (WIM) and compact HII regions suggests that there is a major gap in our understanding of the interstellar gas. Our goal is to investigate the properties of the dense warm ionized medium in the Milky Way using spectrally resolved SOFIA GREAT [NII] 205um fine-structure lines and Green Bank Telescope hydrogen radio recombination lines (RRL) data, supplemented by spectrally unresolved Herschel PACS [NII] 122um data, and spectrally resolved ^12^CO. We observed eight lines of sight (LOS) in the 20{deg}<l<30{deg}region in the Galactic plane. We spectrally unresolved Herschel PACS [NII] 122um data, and spectrally resolved ^12^CO. Methods. We observed eight lines of sight (LOS) in the 20{deg}<l<30{deg}region in the Galactic plane. We analyzed spectrally resolved lines of [NII] at 205um and RRL observations, along with the spectrally unresolved Herschel PACS 122um emission, using excitation and radiative transfer models to determine the physical parameters of the dense warm ionized medium. We derived the kinetic temperature, as well as the thermal and turbulent velocity dispersions from the [NII] and RRL linewidths. The regions with [NII] 205um emission are characterized by electron densities, n(e)~10-35cm^-3^, temperatures range from 3400 to 8500K, and nitrogen column densities N(N^+^)~7x10^16^ to 3x10^17^cm^-2^. The ionized hydrogen column densities range from 6x10^20^ to 1.7x10^21^cm^-2^ and the fractional nitrogen ion abundance x(N^+^)~1.1x10^-4^ to 3.0x10^-4^, implying an enhanced nitrogen abundance at a distance ~4.3kpc from the Galactic Center. The [NII] 205um emission lines coincide with CO emission, although often with an offset in velocity, which suggests that the dense warm ionized gas is located in, or near, star-forming regions, which themselves are associated with molecular gas. These dense ionized regions are found to contribute >~50% of the observed [CII] intensity along these LOS. The kinetic temperatures we derive are too low to explain the presence of N^+^ resulting from electron collisional ionization and/or proton charge transfer of atomic nitrogen. Rather, these regions most likely are ionized by extreme ultraviolet (EUV) radiation from nearby star-forming regions or as a result of EUV leakage through a clumpy and porous interstellar medium.2021A&A...651A..59Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/651/A59CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/814/133 : Herschel Galactic plane survey of [NII] (Goldsmith+, 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/651/A59https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/651/A59http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/651/A59https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/651/A59https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/651/A59http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/651/A59GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/651/A59/list (List of tables)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/651/A59/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/651/A59/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/651/A59/list?GETtext/xml+votable180.050000true277.294102-10.7186040.0055555555555555566/29522 29529 29533 29535 30218-30219 30244 30258https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/651/A59?format=asciidefaultJ/A+A/651/A59/listList of tablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameEight lines of sight name (GLLL.ll+B.b)meta.id;meta.maincharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latTableName of the table with velocities and main beam temperaturesmeta.id;phys.temperature;meta.tablechar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexedJ/A+A/651/A59/g020p9+0G020.9+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g021p7+0G021.7+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g023p5+0G023.5+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g024p3+0G024.3+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g025p2+0G025.2+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g026p1+0G026.1+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g027p0+0G027.0+0.0 velocities and main beam temperaturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloatV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullableJ/A+A/651/A59/g028p7+0G028.7+0.0 velocities and main beam temperaturesV([CII])? [CII] LSR velocity (3)km/sspect.dopplerVeloc;pos.lsrdoublenullableT([CII])? [CII] main beam antenna temperature (3)Kphys.temperaturefloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintV([NII])? [NII] LSR velocity (1)km/smeta.id;meta.mainfloatnullableT([NII])? [NII] main beam antenna temperature (1)Kphys.temperaturefloatnullableV(RRL)RRL LSR velocity (2)km/sspect.dopplerVeloc;pos.lsrfloatT(RRL)RRL main beam antenna temperature (2)mKphys.temperaturefloat