J/MNRAS/428/3355ivo://CDS.VizieR/J/MNRAS/428/3355doi:10.26093/cds/vizier.74283355CDSHeiner J.S.Sanchez-Gallego J.R.Rousseau-Nepton L.Knapen J.H.2024-07-20T20:13:32Z2014-04-04T14:15:28ZCDS support team

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

cds-question@unistra.frgalaxiesh-i-line-emissionultraviolet-astronomyUsing a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic discs. We present a new, flexible and fully automated procedure using this simple model. This automated method will allow us to take full advantage of a host of available data on galaxies in order to calculate the total hydrogen volume densities of the giant molecular clouds surrounding sites of recent star formation. Until now this was only possible on a galaxy-by-galaxy basis using by-eye analysis of candidate photodissociation regions. We test the automated method by adopting various models for the dust-to-gas ratio and comparing the resulting densities for M74, including a new metallicity map of M74 produced by integral field spectroscopy. We test the procedure against previously published M83 volume densities based on the same method and find no significant differences. The range of total hydrogen volume densities obtained for M74 is approximately 5-700cm^-3^. Different dust-to-gas ratio models do not result in measurably different densities. The cloud densities presented here mean that M74 is added to the list of galaxies analysed using the assumption of photodissociated atomic hydrogen occurring near sites of recent star formation, and consolidate the method. For the first time, full metallicity maps are included in the analysis as opposed to metallicity gradients. The results will need to be compared with other tracers of the interstellar medium and photodissociation regions, such as CO and CII, in order to test our basic assumptions, specifically our assumption that the HI we detect originates in photodissociation regions.2013MNRAS.428.3355Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/428/3355CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/416/2 : Photodissociation regions in M33 (Heiner+, 2011)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/428/3355https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/428/3355http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/428/3355https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/428/3355https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/428/3355http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/428/3355GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/428/3355/ngc5236 (NGC 5236 locations and properties of candidate PDRs (PhotoDissociation Regions))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/428/3355/ngc5236?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/428/3355/ngc5236?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/428/3355/ngc5236?GETtext/xml+votable180.050000true204.2898-29.81870.005555555555555556Cone search capability for table J/MNRAS/428/3355/ngc628pi (NGC 628 locations and properties of candidate PDRs with densities derived from PINGS metallicities)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/428/3355/ngc628pi?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/428/3355/ngc628pi?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/428/3355/ngc628pi?GETtext/xml+votable180.050000true24.16133315.7394250.005555555555555556Cone search capability for table J/MNRAS/428/3355/ngc628po (NGC 628 locations and properties of candidate PDRs with densities derived from metallicity slope)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/428/3355/ngc628po?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/428/3355/ngc628po?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/428/3355/ngc628po?GETtext/xml+votable180.050000true24.161315.7394250.005555555555555556Cone search capability for table J/MNRAS/428/3355/ngc628sl (NGC 628 locations and properties of candidate PDRs with densities derived from SpIOMM metallicities)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/428/3355/ngc628sl?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/428/3355/ngc628sl?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/428/3355/ngc628sl?GETtext/xml+votable180.050000true24.161315.7394250.0055555555555555566/18398 43881https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/428/3355?format=asciiUVRadiodefaultJ/MNRAS/428/3355/ngc5236NGC 5236 locations and properties of candidate PDRs (PhotoDissociation Regions)G/GbgSource contrastphot.flux;arith.ratiofloatG0Incident flux (scaled to solar neighborhood)phot.flux;em.UVfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPDRID[1/172] Photo-Dissociation Region (PDR) identification numbermeta.id;meta.mainintNpNumber of patches for this photo-dissociation regionmeta.numberintnullableRgalGalactocentric distancekpcpos.distance;pos.galactocentricfloatRnormNormalized radius in R_25_ units (1)pos.angDistancefloatNHIHI column densitycm**-2phys.columnDensitydoublee_NHIrms uncertainty on NHIcm**-2stat.errordoubled/d0Dust-to-gas ratio log({delta}/{delta}_0_), scaled to solar neighborhood (2)stat.paramfloate_d/d0? rms uncertainty on d/d0stat.errorfloatnullablerhoHISource-patch separationpcpos.distance;phys.sizefloate_rhoHIrms uncertainty on rhoHIpcstat.errorfloatFluxFlux of PDR (erg/cm^2^/s/{AA})cW.m**-2.nm**-1phot.flux.density;em.optdoublee_Flux? rms uncertainty on FluxcW.m**-2.nm**-1stat.error;phot.fluxdoublenullablenHTotal HI volume densitycm**-3phys.densityfloate_nH? rms uncertainty on nHcm**-3stat.errorfloatnullableRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declinaton (J2000)degpos.eq.dec;meta.mainRApdegPatch right ascension (J2000)degpos.eq.raDEpdegPatch declination (J2000)degpos.eq.decJ/MNRAS/428/3355/ngc628piNGC 628 locations and properties of candidate PDRs with densities derived from PINGS metallicitiesNHIHI column densitycm**-2phys.columnDensitydoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPDRID[1/172] Photo-Dissociation Region (PDR) identification numbermeta.id;meta.mainintNpNumber of patches and corresponding H volume densities For the 3 methodsmeta.bib.volumeintnullableRgalGalactocentric distancekpcpos.distance;pos.galactocentricfloatRnormNormalized radius in R_25_ units (1)pos.angDistancefloate_NHIrms uncertainty on NHIcm**-2stat.errordoubled/d0Dust-to-gas ratio log({delta}/{delta}_0_), scaled to solar neighborhood (2)stat.paramfloate_d/d0? rms uncertainty on d/d0stat.errorfloatnullablerhoHISource-patch separationpcpos.distance;phys.sizefloate_rhoHIrms uncertainty on rhoHIpcstat.errorfloatFluxFlux of PDR (erg/cm^2^/s/{AA})cW.m**-2.nm**-1phot.flux.density;em.optdoublee_Flux? rms uncertainty on FluxcW.m**-2.nm**-1stat.error;phot.fluxdoublenullableG0Incident flux (scaled to solar neighborhood)phot.flux;em.UVfloatG/GbgSource contrastphot.flux;arith.ratiofloatnHTotal HI volume densitycm**-3phys.densityfloate_nH? rms uncertainty on nHcm**-3stat.errorfloatnullableRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declinaton (J2000)degpos.eq.dec;meta.mainRApdegPatch right ascension (J2000)degpos.eq.raDEpdegPatch declination (J2000)degpos.eq.decJ/MNRAS/428/3355/ngc628poNGC 628 locations and properties of candidate PDRs with densities derived from metallicity sloperecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPDRID[1/172] Photo-Dissociation Region (PDR) identification numbermeta.id;meta.mainintNpNumber of patches and corresponding H volume densities For the 3 methodsmeta.bib.volumeintnullableRgalGalactocentric distancekpcpos.distance;pos.galactocentricfloatRnormNormalized radius in R_25_ units (1)pos.angDistancefloatNHIHI column densitycm**-2phys.columnDensitydoublee_NHIrms uncertainty on NHIcm**-2stat.errordoubled/d0Dust-to-gas ratio log({delta}/{delta}_0_), scaled to solar neighborhood (2)stat.paramfloate_d/d0? rms uncertainty on d/d0stat.errorfloatnullablerhoHISource-patch separationpcpos.distance;phys.sizefloate_rhoHIrms uncertainty on rhoHIpcstat.errorfloatFluxFlux of PDR (erg/cm^2^/s/{AA})cW.m**-2.nm**-1phot.flux.density;em.optdoublee_Flux? rms uncertainty on FluxcW.m**-2.nm**-1stat.error;phot.fluxdoublenullableG0Incident flux (scaled to solar neighborhood)phot.flux;em.UVfloatG/GbgSource contrastphot.flux;arith.ratiofloatnHTotal HI volume densitycm**-3phys.densityfloate_nH? rms uncertainty on nHcm**-3stat.errorfloatnullableRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declinaton (J2000)degpos.eq.dec;meta.mainRApdegPatch right ascension (J2000)degpos.eq.raDEpdegPatch declination (J2000)degpos.eq.decJ/MNRAS/428/3355/ngc628slNGC 628 locations and properties of candidate PDRs with densities derived from SpIOMM metallicitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPDRID[1/172] Photo-Dissociation Region (PDR) identification numbermeta.id;meta.mainintNpNumber of patches and corresponding H volume densities For the 3 methodsmeta.bib.volumeintnullableRgalGalactocentric distancekpcpos.distance;pos.galactocentricfloatRnormNormalized radius in R_25_ units (1)pos.angDistancefloatNHIHI column densitycm**-2phys.columnDensitydoublee_NHIrms uncertainty on NHIcm**-2stat.errordoubled/d0Dust-to-gas ratio log({delta}/{delta}_0_), scaled to solar neighborhood (2)stat.paramfloate_d/d0? rms uncertainty on d/d0stat.errorfloatnullablerhoHISource-patch separationpcpos.distance;phys.sizefloate_rhoHIrms uncertainty on rhoHIpcstat.errorfloatFluxFlux of PDR (erg/cm^2^/s/{AA})cW.m**-2.nm**-1phot.flux.density;em.optdoublee_Flux? rms uncertainty on FluxcW.m**-2.nm**-1stat.error;phot.fluxdoublenullableG0Incident flux (scaled to solar neighborhood)phot.flux;em.UVfloatG/GbgSource contrastphot.flux;arith.ratiofloatnHTotal HI volume densitycm**-3phys.densityfloate_nH? rms uncertainty on nHcm**-3stat.errorfloatnullableRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declinaton (J2000)degpos.eq.dec;meta.mainRApdegPatch right ascension (J2000)degpos.eq.raDEpdegPatch declination (J2000)degpos.eq.dec