J/A+A/579/A71ivo://CDS.VizieR/J/A+A/579/A71doi:10.26093/cds/vizier.35790071CDSCesaroni R.Pestalozzi M.Beltran M.T.Hoare M.G.Molinari S.Olmi L.,Smith M.D.Stringfellow G.S.Testi L.Thompson M.A.2017-03-13T08:17:01Z2015-11-17T14:22:59ZCDS support team

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

cds-question@unistra.frh-ii-regionsearly-type-starsinfrared-photometryInvestigating the relationship between radio and infrared emission of HII regions may help shed light on the nature of the ionizing stars and the formation mechanism of early-type stars in general. We have taken advantage of recent unbiased surveys of the Galactic plane such as Herschel/Hi-GAL and VLA/CORNISH to study a bona fide sample of young HII regions located in the Galactic longitude range 10{deg}-65{deg} by comparing the mid- and far-IR continuum emission to the radio free-free emission at 5GHz. We have identified the Hi-GAL counterparts of 230 CORNISH HII regions and reconstructed the spectral energy distributions of 204 of these by complementing the Hi-GAL fluxes with ancillary data at longer and shorter wavelengths. Using literature data, we obtained a kinematical distance estimate for 200 HII regions with Hi-GAL counterparts and determined their luminosities by integrating the emission of the corresponding spectral energy distributions. We have also estimated the mass of the associated molecular clumps from the (sub)millimeter flux densities. Our main finding is that for ~1/3 of the HII regions the Lyman continuum luminosity appears to be greater than the value expected for a zero-age main-sequence star with the same bolometric luminosity. This result indicates that a considerable fraction of young, embedded early-type stars presents a "Lyman excess" possibly due to UV photons emitted from shocked material infalling onto the star itself and/or a circumstellar disk. Finally, by comparing the bolometric and Lyman continuum luminosities with the mass of the associated clump, we derive a star formation efficiency of 5%. The results obtained suggest that accretion may still be present during the early stages of the evolution of HII regions, with important effects on the production of ionizing photons and thus on the circumstellar environment. More reliable numerical models describing the accretion process onto massive stars are required to shed light on the origin of the observed Lyman excess.2015A&A...579A..71Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/579/A71CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/205/1 : CORNISH project. II. Source catalog (Purcell+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/579/A71https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/579/A71http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/579/A71https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/579/A71https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/579/A71http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/579/A71GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/579/A71/tablea1 (Flux density densities of the HII regions classified as "ultracompact" and "compact" in the CORNISH catalogue)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/579/A71/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/579/A71/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/579/A71/tablea1?GETtext/xml+votable180.050000true272.323-20.12310.0055555555555555565/7377 7578 7605 7654 6/14354-14355 14357-14359 14365 14413 29091 29094-29095 29097 29100-29101 29112 29114-29115 29461 29504-29505 29507 29517 29522 29529 29532-29533 29535 30218-30219 30222 30240-30241 30244-30245 30256 30258-30259 30262-30263 30268-30269 30316 30318-30319 30405 30416 30594 30600 30604-30605 30622 30640-30641 30644 30691 30694-30695 30701 30714 30718-307193.313034785154005e-24 9.459244267764888e-21https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/579/A71?format=asciiInfrareddefaultJ/A+A/579/A71/tablea1Flux density densities of the HII regions classified as "ultracompact" and "compact" in the CORNISH cataloguerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTA2indicates parameters in tablea2meta.ref.urlcharSeqSequential numbermeta.recordintprimaryNameCORNISH name, GLLL.llll+BB.bbbbmeta.id;meta.maincharRAJ2000CORNISH right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000CORNISH declination (J2000)degpos.eq.dec;meta.mainS5GHzFlux density at 5GHzmJyphot.flux.density;em.radio.3-6GHzfloatRAHdeg? Hi-GAL right ascension (J2000)degpos.eq.ranullablen_RAHdeg[a] Note when no position (1)meta.notecharDEHdeg? Hi-GAL declination (J2000)degpos.eq.decnullablen_DEHdeg[a] Note when no position (1)meta.notecharS21um? Flux density at 21um (2)Jyphot.flux.density;em.IR.15-30umfloatnullableS22um? Flux density at 22um (2)Jyphot.flux.density;em.IR.15-30umfloatnullableS70um? Flux density at 70um (2)Jyphot.flux.density;em.IR.30-60umdoublenullableS160um? Flux density at 160um (2)Jyphot.flux.density;em.mm.1500-3000GHzfloatnullableS250um? Flux density at 250um (2)Jyphot.flux.density;em.mm.750-1500GHzfloatnullableS350um? Flux density at 350um (2)Jyphot.flux.density;em.mm.750-1500GHzfloatnullableS500um? Flux density at 500um (2)Jyphot.flux.density;em.mm.400-750GHzfloatnullableS870um? Flux density at 870um (2)Jyphot.flux.density;em.mm.200-400GHzfloatnullableS1100um? Flux density at 1100um (2)Jyphot.flux.density;em.mm.200-400GHzfloatnullableJ/A+A/579/A71/tablea2Distances, Lyman continuum photon rates, bolometric luminosities, and clump masses of the 200 HII regions of our sample for which a distance estimate was possibledDistancekpcpos.distance;pos.heliocentricfloatn_d[a] Note on d (1)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqSequential numbermeta.recordintlog10NLyLyman continuum photon ratelog(s**-1)phot.count;em.X-rayfloatlog10LBolometric luminositylog(solLum)phys.luminosityfloatlog10MgasClump masslog(solMass)phys.massfloat