J/MNRAS/478/5579ivo://CDS.VizieR/J/MNRAS/478/5579doi:10.26093/cds/vizier.74785579CDSMarshall B.Kerton C.R.2024-08-18T20:20:26Z2022-02-08T12:50:24ZCDS support team

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

cds-question@unistra.frh-ii-regionsmillimeter-astronomysubmillimeter-astronomyA large number (67) of the compact/ultra-compact HII regions identified in the Coordinated Radio and Infrared Survey for High-Mass Star Formation catalogue were determined to be powered by a Lyman continuum flux in excess of what was expected given their corresponding luminosity. In this study we attempt to reasonably explain the Lyman excess phenomenon in as many of the 67 HII regions as possible through a variety of observational and astrophysical means including new luminosity estimates, new Herschel photometry, new distance determinations, the use of different models for dust and ionized gas covering factors, and the use of different stellar calibrations. This phenomenon has been observed before; however, the objects shown to exhibit this behaviour in the literature have decidedly different physical properties than the regions in our sample, and thus the origin of the excess is not the same. We find that the excess can be reproduced using OB stellar atmosphere models that have been slightly modified in the extreme ultraviolet. Though the exact mechanism producing the excess is still uncertain, we do find that a scaled up magnetospheric accretion model, often used to explain similar emission from T Tauri stars, is unable to match our observations. Our results suggest that the Lyman excess may be associated with younger HII regions, and that it is more commonly found in early B-type stars. Our refined sample of 24 Lyman excess HII regions provides an ideal sample for comparative studies with regular HII regions, and can act as the basis for the further detailed study of individual regions.2018MNRAS.478.5579Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/478/5579CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/579/A71 : Infrared emission of young HII regions (Cesaroni+, 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/478/5579https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/478/5579http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/478/5579https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/478/5579https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/478/5579http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/478/5579GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/478/5579/table4 (The refined LERs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/478/5579/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/478/5579/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/478/5579/table4?GETtext/xml+votable180.050000true272.347026-20.1352860.0055555555555555566/14355 29091 29097 29100 29112 29114 29510-29511 29532 30218 30245 30258 30312 30319 30420 30423 30718-307193.972892068905477e-22 2.837779945223663e-21https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/478/5579?format=asciiMillimeterdefaultJ/MNRAS/478/5579/table3New flux densities for the 67 LERs categorized by C15 ( Cesaroni et al., 2015A&A...579A..71C)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintC15Cesaroni et al. (2015A&A...579A..71C, Cat. J/A+A/579/A71) identification numbermeta.id;meta.mainintS70umFlux density at 70umJyphot.flux.density;em.IR.30-60umfloatS160umFlux density at 160umJyphot.flux.density;em.mm.1500-3000GHzdoubleS250umFlux density at 250umJyphot.flux.density;em.mm.750-1500GHzfloatS350umFlux density at 350umJyphot.flux.density;em.mm.750-1500GHzfloatS500umFlux density at 500umJyphot.flux.density;em.mm.400-750GHzfloatJ/MNRAS/478/5579/table4The refined LERsSpTypeZAMS spectral type (1)src.spTypecharalpha? Spectral index (2)spect.indexfloatnullablee_alpha? Spectral index error (2)stat.error;pos.eq.rafloatnullable_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.decnullableindexedSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintC15Cesaroni et al. (2015A&A...579A..71C, Cat. J/A+A/579/A71) identification numbermeta.id;meta.mainintCORNISHCORNISH designation (GLLL.llll+BB.bbbb)meta.idcharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latlogLlog10 Luminositylog(solLum)phys.luminosityfloatlog(NLy)log10 ionizing photon fluxlog(s**-1)phot.fluxfloatdDistance (reflect our new photometry and new kinematic distances)kpcpos.distancefloatrRadius determined using Spitzer 8um imagespcpos.distance;phys.sizefloatneElectron density1000cm**-3phys.density;phys.electronfloatJ/MNRAS/478/5579/tablea1Sources removed from the original LER samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintC15Cesaroni et al. (2015A&A...579A..71C, Cat. J/A+A/579/A71) identification numbermeta.id;meta.mainintCORNISHCORNISH designation (GLLL.llll+BB.bbbb)meta.idcharlogLlog10 Luminositylog(solLum)phys.luminosityfloatlogNLylog10 photon fluxlog(s**-1)phot.fluxfloatdDistance value based on our new photometry and kinematic distancekpcpos.distancefloatneElectron density1000cm**-3phys.density;phys.electronfloatNotesNotes (1)meta.notechar