J/A+A/706/A280ivo://CDS.VizieR/J/A+A/706/A280CDSKhan S.Jacob A.M.Rugel M.R.Urquhart J.S.Neupane S.Wyrowski F.,Brunthaler A.Pandian J.D.Gong Y.Barlach Christensen I.Menten K.M.2026-03-02T06:25:50Z2026-02-18T08:01:33ZCDS support team

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

cds-question@unistra.frmilky-way-galaxyh-ii-regionsradio-continuum-emissionspectroscopyMassive stars strongly impact their natal environments and influence subsequent star formation through feedback mechanisms including shocks, outflows and radiation. HII regions are key laboratories for studying this impact. To understand such feedback, it is crucial to characterize the physical conditions of the dense molecular gas in which these regions are embedded. We aim to constrain the kinetic temperature and H_2_ volume density of massive star-forming clumps associated with HII regions using multiple p-H_2_CO transitions. The non-LTE analysis yielded kinetic temperatures (Tkin) ranging from 33.7K to 265K and H_2_ densities (n(H_2_)) between 0.8x10^4^ to 1.05x10^7^cm^-3^, providing a detailed characterization of the dense molecular gas contained in these clumps. We observed the JKaKc transitions of p-H_2_CO (within its J=3-2 and 4-3 states) with the Atacama Pathfinder EXperiment (APEX) 12m submillimeter telescope, using the nFLASH230 and SEPIA345 receivers toward a sample of 61 HII regions. We derived spectral line parameters via multicomponent Gaussian fitting, which was then used to constrain the physical conditions determined using PyRADEX, a non-local thermodynamic equilibrium (LTE) radiative transfer code in combination with Markov chain Monte Carlo analysis. The non-LTE analysis yielded kinetic temperatures (Tkin) ranging from 33.7K to 265K and H_2_ densities (n(H_2_)) between 0.8x10^4^ and 1.05x10^7^cm^-3^, providing a detailed characterization of the dense -olecular gas contained in these clumps. In addition to the p-H_2_CO emission arising from the targeted clump, a large fraction (57%) of the sources exhibited multiple p-H_2_CO components, with the secondary components being characterized by a higher Tkin and broader line widths. Investigation of the nature of the secondary component revealed its association with supersonic nonthermal motions and turbulent gas. When comparing the physical properties of the molecular gas and dust components with those of the ionized gas, we found that parameters directly linked to the central high-mass star, such as bolometric luminosity (Lbol) and Lyman continuum photon rate (NLyc), show stronger and more systematic correlations. These findings emphasize the role of the central star in governing the interplay between the molecular and ionized gas. In our sample of HII regions, the pressure of the neutral gas systematically exceeds that of the ionized gas. This suggests that the surrounding neutral molecular medium can hinder or slow down the expansion of HII regions due to its higher pressure. However, given the limited spatial resolution, a definitive conclusion on the role of molecular gas in confining HII regions cannot be made until high resolution observations are obtained.2026A&A...706A.280Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/706/A280CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/565/A75 : ATLASGAL: dust condensations in Galactic planeJ/A+A/611/A6 : ATLASGAL massive clumps H_2_CO data (Tang+, 2018)J/MNRAS/473/1059 : Complete sample of Galactic clump propertiesJ/A+A/627/A175 : GLOSTAR. Radio Source Catalogue I (Medina+, 2019)J/MNRAS/510/3389 : High-mass star formation evolutionary trendsJ/A+A/689/A196 : GLOSTAR GPS. Radio source catalog (Medina+, 2024)J/A+A/689/A81 : GLOSTAR GPS. X. Galactic HII region catalog (Khan+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/706/A280https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/706/A280http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/706/A280https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/706/A280https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/706/A280http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/706/A280GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/706/A280/tablec1 (Line fitting parameters of the p-H_2_CO lines observed with nFLASH230)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/706/A280/tablec1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/706/A280/tablec1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/706/A280/tablec1?GETtext/xml+votable180.050000true96.7843198-59.22606790.0055555555555555566/37363 37367-37369 37372 37501 37567 37582-37583 37586 37588 37592 37594 37601-37604 37608-37609 37654-37655 37657 37659-37660 37667 37669 37672-37673 37999 38009 38031 38038 38049 38081 38173 38178-38179 38226 38934 38937 38957https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/706/A280?format=asciiRadiodefaultJ/A+A/706/A280/tablec1Line fitting parameters of the p-H_2_CO lines observed with nFLASH230recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAllDisplay data for all the tablesmeta.ref.urlcharGLOSTARName of the HII region in the GLOSTAR RRL catalog (G1)meta.id;meta.maincharATLASGALName of the associated ATLASGAL clumpmeta.idcharcomponent[abc] Secondary component name (G2)meta.code.multipcharetanFLASHBeam filling factor for nFLASH observationarith.factor;stat.filling;instr.beamfloatVlsr? Velocity of the component obtained from H_2_CO(303-202)km/sphys.veloc;pos.lsrfloatnullableTmbH2CO1? Amplitude of the component of H_2_CO(303-202)Kphot.antennaTempfloatnullable_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.raindexed_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.decindexede_TmbH2CO1? Error in the amplitude of the component of H_2_CO(303-202)Kstat.errorfloatnullabletdvH2CO1? Integrated intensity of the component of H_2_CO(303-202)K.km/sphot.flux.densityfloatnullablee_tdvH2CO1? Error in the Integrated intensity of the component of H_2_CO(303-202)K.km/sstat.errorfloatnullableWH2CO1? Linewidth of the component of H_2_CO(303-202)km/sspect.line.widthfloatnullablee_WH2CO1? Error in the Linewidth of the component of H_2_CO(303-202)km/sstat.errorfloatnullableTmbH2CO2? Amplitude of the component of H_2_CO(322-221)Kphot.antennaTempfloatnullablee_TmbH2CO2? Error in the Amplitude of the component of H_2_CO(322-221)Kstat.errorfloatnullabletdvH2CO2? Integrated intensity of the component of H_2_CO(322-221)K.km/sphot.flux.densityfloatnullablee_tdvH2CO2? Error in the Integrated intensity of the component of H_2_CO(322-221)K.km/sstat.errorfloatnullableWH2CO2? Linewidth of the component of H_2_CO(322-221)km/sspect.line.widthfloatnullablee_WH2CO2? Error in the Linewidth of the component of H_2_CO(322-221)km/sstat.errorfloatnullableTmbH2CO3? Amplitude of the component of H_2_CO(321-220)Kphot.antennaTempfloatnullablee_TmbH2CO3? Error in the Amplitude of the component of H_2_CO(321-220)Kstat.errorfloatnullabletdvH2CO3? Integrated intensity of the component of H_2_CO(321-220)K.km/sphot.flux.densityfloatnullablee_tdvH2CO3? Error in the Integrated intensity of the component of H_2_CO(321-220)K.km/sstat.errorfloatnullableWH2CO3? Linewidth of the component of H_2_CO(321-220)km/sspect.line.widthfloatnullablee_WH2CO3? Error in the Linewidth of the component of H_2_CO(321-220)km/sstat.errorfloatnullable_GlonPositions from Khan et al., 2024, Cat. J/A+A/689/A81 (longitude part)degpos.galactic.lon_GlatPositions from Khan et al., 2024, Cat. J/A+A/689/A81 (latitude part)degpos.galactic.latJ/A+A/706/A280/tablec2Line fitting parameters of the p-H_2_CO lines observed with SEPIA345AllDisplay data for all the tablesmeta.ref.urlcharGLOSTARName of the HII region in the GLOSTAR RRL catalog (G1)meta.id;meta.maincharATLASGALName of the associated ATLASGAL clumpmeta.idcharcomponent[abc] Secondary component name (G2)meta.code.multipcharetaSEPIABeam filling factor for SEPIA observationarith.factor;stat.filling;instr.beamfloatVlsr? Velocity of the component obtained from H_2_CO(303-202)km/sphys.veloc;pos.lsrfloatnullableTmbH2CO4? Amplitude of the component of H_2_CO(404-303)Kphot.antennaTempfloatnullablee_TmbH2CO4? Error in the Amplitude of the component of H_2_CO(404-303)Kstat.errorfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordinttdvH2CO4? Integrated intensity of the component of H_2_CO(404-303)K.km/sphot.flux.densityfloatnullablee_tdvH2CO4? Error in the Integrated intensity of the component of H_2_CO(404-303)K.km/sstat.errorfloatnullableWH2CO4? Linewidth of the component of H_2_CO(404-303)km/sspect.line.widthfloatnullablee_WH2CO4? Error in the Linewidth of the component of H_2_CO(404-303)km/sstat.errorfloatnullableTmbH2CO5? Amplitude of the component of H_2_CO(423-322)Kphot.antennaTempfloatnullablee_TmbH2CO5? Error in the Amplitude of the component of H_2_CO(423-322)Kstat.errorfloatnullabletdvH2CO5? Integrated intensity of the component of H_2_CO(423-322)K.km/sphot.flux.densityfloatnullablee_tdvH2CO5? Error in the Integrated intensity of the component of H_2_CO(423-322)K.km/sstat.errorfloatnullableWH2CO5? Linewidth of the component of H_2_CO(423-322)km/sspect.line.widthfloatnullablee_WH2CO5? Error in the Linewidth of the component of H_2_CO(423-322)km/sstat.errorfloatnullableTmbH2CO6? Amplitude of the component of H_2_CO(422-321)Kphot.antennaTempfloatnullablee_TmbH2CO6? Error in the Amplitude of the component of H_2_CO(422-321)Kstat.errorfloatnullabletdvH2CO6? Integrated intensity of the component of H_2_CO(422-321)K.km/sphot.flux.densityfloatnullablee_tdvH2CO6? Error in the Integrated intensity of the component of H_2_CO(422-321)K.km/sstat.errorfloatnullableWH2CO6? Linewidth of the component of H_2_CO(422-321)km/sspect.line.widthfloatnullablee_WH2CO6? Error in the Linewidth of the component of H_2_CO(422-321)km/sstat.errorfloatnullableJ/A+A/706/A280/tablec3Derived physical properties of molecular cloudsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAllDisplay data for all the tablesmeta.ref.urlcharGLOSTARName of the HII region in the GLOSTAR RRL catalog (G1)meta.id;meta.maincharATLASGALName of the associated ATLASGAL clumpmeta.idcharcomponentSecondary component name (G2)meta.code.multipcharTkin? Non-LTE Kinetic temperatureKphys.temperaturefloatnullableE_Tkin? Upper error in the non-LTE Kinetic temperatureKstat.error;stat.maxfloatnullablee_Tkin? Lower error in the non-LTE Kinetic temperatureKstat.errorfloatnullablelognH2? Log of H_2_ densitylog(cm**-3)phys.densityfloatnullableE_lognH2? Log of upper error in the H_2_ densitylog(cm**-3)stat.error;stat.maxfloatnullablee_lognH2? Log of lower error in the H_2_ densitylog(cm**-3)stat.errorfloatnullablelogNH2CO? Log of para-H_2_CO column densitylog(cm**-2)phys.columnDensityfloatnullableE_logNH2CO? Log of upper error in the para-H_2_CO column densitylog(cm**-2)stat.error;stat.maxfloatnullablee_logNH2CO? Log of lower error in the para-H_2_CO column densitylog(cm**-2)stat.errorfloatnullablelogXH2CO? Log of fractional abundance of para-H_2_COphys.abundfloatnullablelogNH2? Log of H_2_ column densitylog(cm**-2)phys.columnDensityfloatnullable