J/MNRAS/482/2681ivo://CDS.VizieR/J/MNRAS/482/2681doi:10.26093/cds/vizier.74822681CDSYang A.Y.Thompson M.A.Tian W.W.Bihr S.Beuther H.Hindson L.2024-08-19T20:14:52Z2022-08-02T08:59:09ZCDS support team

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

cds-question@unistra.frinterstellar-mediumh-ii-regionsinfrared-astronomyradio-continuum-emissionmillimeter-astronomysubmillimeter-astronomyWe have carried out the largest and most unbiased search for hypercompact (HC) HII regions. Our method combines four interferometric radio continuum surveys (THOR, CORNISH, MAGPIS, and White2005) with far-infrared and sub-mm Galactic Plane surveys to identify embedded HII regions with positive spectral indices; 120 positive spectrum HII regions have been identified from a total sample of 534 positive spectral index radio sources. None of these HII regions, including the known HC HII regions recovered in our search, fulfills the canonical definition of an HC HII region at 5GHz. We suggest that the current canonical definition of HC HII regions is not accurate and should be revised to include a hierarchical structure of ionized gas that results in an extended morphology at 5GHz. Correlating our search with known ultracompact (UC) HII region surveys, we find that roughly half of detected UC HII regions have positive spectral indices, instead of more commonly assumed flat and optically thin spectra. This implies a mix of optically thin and thick emission and has important implications for previous analyses which have so far assumed optically thin emission for these objects. Positive spectrum HII regions are statistically more luminous and possess higher Lyman continuum fluxes than HII regions with flat or negative indices. Positive spectrum HII regions are thus more likely to be associated with more luminous and massive stars. No differences are found in clump mass, linear diameter, or luminosity-to-mass ratio between positive spectrum and non-positive spectrum HII regions.2019MNRAS.482.2681Yhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/482/2681CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/482/2681https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/482/2681http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/482/2681https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/482/2681https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/482/2681http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/482/2681GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/482/2681/tablea1 (Information of 120 young positive spectrum HII regions)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/482/2681/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/482/2681/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/482/2681/tablea1?GETtext/xml+votable180.050000true272.2336287-20.09865350.005555555555555556Cone search capability for table J/MNRAS/482/2681/tablea2 (Information of total 534 positive spectrum radio objects)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/482/2681/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/482/2681/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/482/2681/tablea2?GETtext/xml+votable180.050000true272.2336287-20.09865350.0055555555555555565/3588-3589 7275 7279 7365 7376-7377 7380 7382 7554 7564-7565 7578 7604-7605 7651 7672 6/12971 12975 12986 14337 14340 14365 14401-14403 14406 14409 14412-14413 29091 29094 29097-29099 29112 29114-29115 29162-29163 29166 29457 29516-29517 29532-29533 29535 29557 30222-30223 30234 30240-30241 30244-30245 30247 30264-30265 30268-30269 30271 30306 30316 30318-30319 30330-30331 30334 30404-30405 30407 30592 30594 30601 30616 30618 30622 30641 30644-30645 30666-30667 30693-30697 30700-30701 30706 30712-30714 30716 30718-307199.276497240453405e-25 3.313034785154005e-24https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/482/2681?format=asciiInfraredMillimeterRadiodefaultJ/MNRAS/482/2681/tablea1Information of 120 young positive spectrum HII regions_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.recordintNameCORNISH source name (GLLL.llll+BB.bbbb)meta.id;meta.maincharf_NameFlag on name (1)meta.codecharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latF5GHzFlux density at 5GHzmJyphot.flux.density;em.radio.3-6GHzdoublee_F5GHzError on F5GHzmJystat.errorfloatADiamAngular diameter at 5GHz from CORNISHarcsecphys.angSize;em.radio.3-6GHzfloate_ADiamError on ADiamarcsecstat.errorfloatF1.4GHzFlux densities at 1.4GHz from THOR, MAGPIS and White et al. (2005AJ....130..586W, Cat. J/AJ/130/586)mJyphot.flux.density;em.radio.750-1500MHzfloate_F1.4GHz? Error on F1.4GHz (2)mJystat.errorfloatnullablealphaSpectral indexspect.indexfloate_alpha? Error on SpIdxstat.error;pos.eq.rafloatnullableJ/MNRAS/482/2681/tablea2Information of total 534 positive spectrum radio objects_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.recordintNameCORNISH source name (GLLL.llll+BB.bbbb)meta.id;meta.maincharf_NameFlag on name (1)meta.codecharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latF5GHzFlux density at 5GHzmJyphot.flux.density;em.radio.3-6GHzdoublee_F5GHzError on F5GHzmJystat.errorfloatADiamAngular diameter at 5GHz from CORNISHarcsecphys.angSize;em.radio.3-6GHzfloate_ADiamError on ADiamarcsecstat.errorfloatF1.4GHzFlux densities at 1.4GHz from THOR, MAGPIS and White et al. (2005AJ....130..586W, Cat. J/AJ/130/586)mJyphot.flux.density;em.radio.750-1500MHzfloate_F1.4GHz? Error on F1.4GHz (2)mJystat.errorfloatnullablealphaSpectral indexspect.indexfloate_alpha? Error on SpIdxstat.error;pos.eq.rafloatnullable