J/ApJS/91/659ivo://CDS.VizieR/J/ApJS/91/659doi:10.26093/cds/vizier.20910659CDSKurtz S.Churchwell E.Wood D.O.S.2013-03-06T05:36:34Z1997-12-09T21:19:49ZCDS support team

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

cds-question@unistra.frh-ii-regionsradio-sourcesRadio continuum observations were made of 59 IRAS sources that have 100{mu}m flux densities >=1000Jy and far-infrared colors identified with ultracompact (UC) HII regions. Eighty percent were found to have associated compact radio sources. Seventy-five sources were detected at <~1" resolution at 3.6 and 2cm wavelengths, for which we provide contour plots and flux density distributions ranging from the radio to the near-infrared. Over half are unresolved and their morphologies undetermined. The remaining sources can be described by only five morphological classes, whose frequency of occurrence is consistent with that of the Wood and Churchwell survey (1989ApJS...69..831W). We calculate physical properties of the nebulae and show that they are consistent with UC photoionized regions. Alternative explanations are explored and found to be unlikely. The correlation of UC HII region positions with proposed spiral arms is examined and found to be well correlated only for the local spiral arm or "spur". No obvious enhancement of UC HII regions is apparent along the proposed Sagittarius and Scutum arms, probably because of inaccuracies in the kinematic distances. We find the latitude distribution of UC HII regions to lie in the range 0.5deg<[b_FWHM_]<=0.8deg. No correlation between size and density of cometary and core-halo UC HII regions is found, consistent with the bow shock interpretation of these morphologies. Spherical and unresolved UC HII regions, however, appear to show a trend toward lower densities with increasing size, as expected for expanding HII regions. The observed ratios of far-infrared to radio flux densities of UC HII regions lie in the range 10^3^ to >=10^5^. By applying the results of model atmospheres, it is shown that this ratio depends on spectral type, ranging from ~10^3^ for an O4 star to >=10^5^ for a B3 star. We find that many of the UC HII regions in our sample must be excited by a cluster of stars, and most probably contain significant amounts of dust.1994ApJS...91..659Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/91/659CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-to1989ApJS...69..831W : Wood and Churchwell, Paper Ihttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/91/659https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/91/659http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/91/659https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/91/659https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/91/659http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/91/659GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/91/659/table3 (Observed Source Parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/91/659/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/91/659/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/91/659/table3?GETtext/xml+votable180.050000true271.55967701-20.528762840.0055555555555555566/3271 3290 3649 14309 14311 14358 14594 14621 14622 14624 14666 14670 14671 14691 14696 14704 15667 15681 15683 21456 22855 23969 23982 24325 29070 29090 29094 29096 29505 29510 30241 30256 30263 30269 30312 30313 30319 30328 30405 30420 30618 30691 30719https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/91/659?format=asciiRadiodefaultJ/ApJS/91/659/table3Observed Source ParametersDmin? Minimum diameter (3)arcsecphys.angSize;srcfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameRadiosource designationmeta.id;meta.maincharMtypeMorphological type (1)src.morph.typecharlambdaObservations wavelength (2 or 3.6)cmem.wl.effectivefloatRA1950Source right ascension (1950) (2)pos.eq.ra;meta.mainDE1950Source declination (1950) (2)pos.eq.dec;meta.mainSPeak? Peak flux density (in mJy/beam)mJyphot.flux.density;em.radio.1500-3000MHzfloatnullableSInt? Integrated flux densitymJyphot.flux.density;em.radio.1500-3000MHzfloatnullableRAbox? Integrated box right ascensionarcsecpos.eq.ranullableDEbox? Integrated box declinationarcsecpos.eq.decnullableDmax? Maximum diameter (3)arcsecphys.angSize;stat.maxfloatnullablen_Dmax[P] P: Ponctual sourcemeta.notecharn_Dmin[P] P: Ponctual sourcemeta.notecharMajHalf-power beam width (HPBW) major axisarcsecphys.angSize;instr.beamfloatMinHalf-power beam width (HPBW) minor axisarcsecphys.angSize;instr.beamfloatMapMap RMS (in mJy/beam)mJystat.stdevfloatNoteNotes (4)meta.notechar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)pos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)pos.eq.decnullableindexed