J/A+A/666/A31ivo://CDS.VizieR/J/A+A/666/A31doi:10.26093/cds/vizier.36660031CDSMeng F.Sanchez-Monge A.Schilke P.Ginsburg A.DePree C.Budaiev N.,Jeff D.Schmiedeke A.Schwoerer A.Veena V.S.Moeller T.2022-10-12T12:10:10Z2022-10-04T09:02:11ZCDS support team

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

cds-question@unistra.frmolecular-cloudsh-ii-regionsradio-sourcesThe giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most massive region with ongoing high-mass star formation in the Galaxy. Two ultra-compact HII (UCHII) regions were identified in SgrB2's central hot cores, SgrB2(M) and SgrB2(N). Our aim is to characterize the properties of the HII regions in the entire SgrB2 cloud. Comparing the HII regions and the dust cores, we aim to depict the evolutionary stages of different parts of SgrB2. We use the Very Large Array in its A, CnB, and D configurations, and in the frequency band C (~6GHz) to observe the whole SgrB2 complex. Using ancillary VLA data at 22.4GHz and ALMA data at 96GHz, we calculated the physical parameters of the UCHII regions and their dense gas environment. We identify 54 UCHII regions in the 6GHz image, 39 of which are also detected at 22.4GHz. Eight of the 54 UCHII regions are newly discovered. The UCHII regions have radii between 0.006pc and 0.04pc, and have emission measure between 10^6^pc/cm^6^ and 10^9^pc/cm^6^. The UCHII regions are ionized by stars of types from B0.5 to O6. We found a typical gas density of ~10^6^-10^9^cm^-3^ around the UCHII regions. The pressure of the UCHII regions and the dense gas surrounding them are comparable. The expansion timescale of these UCHII regions is determined to be ~10^4^-10^5^yr. The percentage of the dust cores that are associated with HII regions are 33%, 73%, 4%, and 1% for SgrB2(N), SgrB2(M), SgrB2(S), and SgrB2(DS), respectively. Two-thirds of the dust cores in SgrB2(DS) are associated with outflows. The electron densities of the UCHII regions we identified are in agreement with that of typical UCHII regions, while the radii are smaller than those of the typical UCHII regions. The dust cores in SgrB2(N) are more evolved than in SgrB2(DS) but younger than in SgrB2(M).2022A&A...666A..31Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/666/A31CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/155/421 : Survey of Galactic Center region at 20cm (Yusef-Zadeh+, 2004)J/ApJS/181/110 : Galactic center X-ray sources (Muno+, 2009)J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)J/A+A/595/A94 : Galactic center clouds temperature structures (Immer+, 2016)J/A+A/586/A50 : Central Molecular Zone H2CO temperature maps (Ginsburg+, 2016)J/A+A/604/A6 : SgrB2 ALMA continuum and spectral index (Sanchez-Monge+, 2017)J/ApJ/853/171 : 3mm point sources in extended Sgr B2 cloud (Ginsburg+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/666/A31https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/666/A31http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/666/A31https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/666/A31https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/666/A31http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/666/A31GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/666/A31/tableb1 (Photometry of UCHII regions in 6, 22.4 and 96GHz)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/666/A31/tableb1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/666/A31/tableb1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/666/A31/tableb1?GETtext/xml+votable180.050000true266.8473125-28.426097220.005555555555555556Cone search capability for table J/A+A/666/A31/list (Infornation on fits image)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/666/A31/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/666/A31/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/666/A31/list?GETtext/xml+votable180.050000true266.83228-28.385280.0055555555555555566/288303.975641742184806e-24 6.36102678749569e-23https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/666/A31?format=asciiRadiodefaultJ/A+A/666/A31/tableb1Photometry of UCHII regions in 6, 22.4 and 96GHzID[1/54] Identifiermeta.id;meta.mainintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintn_ID[ab* ] Note on ID (1)meta.notecharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination sign (J2000)pos.eq.dec;meta.mainr6GHzObserved radius in 6GHzarcsecphys.angSize;srcfloatS66GHzObserved flux in 6GHzmJyphot.flux.density;em.radio.3-6GHzfloate_S66GHzError of observed flux in 6GHzmJystat.errorfloatr22GHz? Observed radius in 22.4GHz (2)arcsecphys.angSize;srcfloatnullableS22GHz? Observed flux in 22.4GHz (2)mJyphot.flux.density;em.radio.12-30GHzfloatnullablee_S22GHz? Error of observed flux in 22.4GHz (2)mJystat.errorfloatnullabler96GHzObserved radius in 96GHzarcsecphys.angSize;srcfloatS96GHzObserved flux in 96GHzmJyphot.flux.density;em.mm.50-100GHzfloate_S96GHzError of observed flux in 96GHzmJystat.errorfloatalpha? Spectral index between 6 and 22.4GHz (2)spect.index;em.radio.12-30GHzfloatnullablee_alpha? Error of spectral index (2)stat.error;pos.eq.rafloatnullableJ/A+A/666/A31/tableb2Derived physical parameters of UCHII regionsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/54] Identifiermeta.id;meta.mainintrcalcCalculated Radius of UCHII regions0.001pcphys.angSize;srcfloatEMEmission measurephys.emissMeasurefloatlog(N'Ly)Log of Lyman continuum fluxlog(s**-1)phot.flux.density;spect.continuumfloatneElectron number density10000cm**-3meta.idfloatnH2? Neutral gas number density in H_2_1e+06cm**-3meta.number;phys.densityfloatnullableriInitial radius of HII regions0.001pcphys.angSize;srcfloatTExpansion-time of HII regions10000yrtime.epochfloatJ/A+A/666/A31/listInfornation on fits imagerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar