J/AJ/169/291ivo://CDS.VizieR/J/AJ/169/291doi:10.26093/cds/vizier/be-59-93CDSYang T.Chen XiXu X.-Y.Yang Y.Chen EnLi J.Ju B.-G.Lu D.-R.2026-07-02T11:52:07Z2026-02-23T15:42:20ZCDS support team

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

cds-question@unistra.frmolecular-cloudsgalaxy-planesmilky-way-galaxyradio-spectroscopystar-forming-regionsco-line-emissionmolecular-physicsWe report the spatial distribution and physical characteristics of molecular clouds in the G24 region, which is located near the intersection of the Milky Way's Galactic bar with the Norma arm and the 3kpc arm. Utilizing molecular line data from the Milky Way Imaging Scroll Painting project, including ^12^CO, ^13^CO and C^18^O, along with our own observations of the HCO^+^ line using the Purple Mountain Observatory 13.7m telescope, we reveal the complex architecture of molecular clouds in the G24 region. Seven giant molecular clouds, each with a mass exceeding 10^4^M_{sun}_ and a typical H_2_ column density of 10^21^cm^-2^, have been identified through observations of CO and its isotopes. The conversion factor X_CO_ for the G24 region is estimated to be 8.25x10^19^cm^-2^ (K.km/s)^-1^, aligning with the typical values observed in other regions. Adopting the GaussClumps algorithm, we identify a total of 257, 201, and 110 clumps in ^12^CO, ^13^CO and C^18^O within the G24 region, respectively. The derived physical properties (including effective radius, mass, and virial parameter) indicate that the majority of these clumps are gravitationally bound, with a subset possessing the potential to form massive stars. Examination of gas infall activities within these clumps further suggests ongoing massive star formation. The complex physical and kinematic environment, shaped by the G24 region's unique location within the Milky Way, has limited the clear detection of gas outflows.2025AJ....169..291Yhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/169/291CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)J/A+A/527/A88 : Chemistry in infrared dark clouds (Vasyunina+, 2011)J/MNRAS/443/1555 : ATLASGAL massive star forming clumps samp. (Urquhart+, 2014)J/A+A/588/A104 : Molecular clouds and star formation (Gong+, 2016)J/MNRAS/471/100 : Hi-GAL compact source catalog. -71.0<l<67.0 (Elia+, 2017)J/ApJ/885/131 : ~200 high-mass SFR plx & proper motion with VLBI (Reid+, 2019)J/other/RAA/20.115 : Molecular clumps CO, HCO and HCN data (Yang+, 2020)J/ApJS/252/20 : CO survey of the CMa OB1 complex (Lin+, 2021)J/ApJS/254/3 : CO obs. of molecular clouds in the MW midplane (Ma+, 2021)J/ApJS/268/1 : CO obs. of mol. clouds in the 3rd Gal. quadrant (Dong+, 2023)J/AJ/167/228 : Physical properties of 221 clumps (Luo+, 2024)J/AJ/168/52 : Infall motion in mol. clumps. V. HCO+ & HCN obs. (Yu+, 2024)http://www.radioast.nsdc.cn/mwisp.php : Milky Way Imaging Scroll Paintinghttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/169/291https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/169/291http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/169/291https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/169/291https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/169/291http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/169/291GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/169/291/tablea1 (The parameters of ^12^CO clumps)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/169/291/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/169/291/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/169/291/tablea1?GETtext/xml+votable180.050000true278.54578-7.30380.005555555555555556Cone search capability for table J/AJ/169/291/tablea2 (The parameters of ^13^CO clumps)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/169/291/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/169/291/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/169/291/tablea2?GETtext/xml+votable180.050000true278.55032-7.301630.005555555555555556Cone search capability for table J/AJ/169/291/tablea3 (The parameters of C^18^O clumps)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/169/291/tablea3?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/169/291/tablea3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/169/291/tablea3?GETtext/xml+votable180.050000true279.20843-7.415760.0055555555555555566/29533 29535 30216 30218 30240https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/169/291?format=asciiMillimeterRadiodefaultJ/AJ/169/291/tablea1The parameters of ^12^CO clumpsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNum[1/257] Clump number (Number)meta.idintMWISP[MWISP] Source name prefixmeta.id.part;meta.maincharSourceSource name defined by Galactic Coordinates (GDD.ddd+D.ddd)meta.id.part;meta.maincharVlsr[78.24/121.62] Central velocitykm/sphys.veloc;pos.lsrfloatdv[0.47/7.51] Linewidth (Delta_v)km/sspect.line.widthfloatMajAx[54/279] Major axis (theta_a)arcsecphys.angSizeint_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.decindexedPA[-64/174] Position angledegpos.posAngintMinAx[71/582] Minor axis (theta_b)arcsecphys.angSizeintDiam[65/354] Diameter (theta_FWHM)arcsecphys.angSizeintDistHC[5.01/7.66] Heliocentric distance (Distance)kpcpos.distancefloatDistGC[3.33/4.13] Galactocentric distance (RGC)kpcpos.distancefloatTex[5.6/23.8] Excitation temperatureKphys.atmol.excitationfloatlog(NH2)[20.4/21.7] Log of hydrogen column densitylog(cm**-2)phys.columnDensityfloatReff[0.6/6.4] Effective radiuspcphys.size.radiusfloatlog(M)[1.7/4] Log of mass (log_Mclump)log(solMass)phys.massfloatlog(Mvir)[1.7/4.2] Log of virial masslog(solMass)phys.virialfloatavir[0.7/12.1] Virial parameter (alpha_vir)phys.mass;arith.ratiofloatlog(Sig)[0.9/2.3] Log of surface density (log_Sigma)log(solMass.pc**-2)phys.densityfloatlog(nH2)[0.6/3.1] Log of number density of hydrogen moleculeslog(cm**-3)phys.densityfloatdvTh[0.1/0.2] Thermal linewidth (Delta_vth)km/sspect.line.widthfloatdvNTh[0.45/7.51] Non-thermal linewidth (Delta_vnth)km/sspect.line.widthfloat_GlonPositions derived from source name (longitude part)degpos.galactic.lon_GlatPositions derived from source name (latitude part)degpos.galactic.latJ/AJ/169/291/tablea2The parameters of ^13^CO clumpsDistHC[5.02/7.49] Heliocentric distance (Distance)kpcpos.distancefloatDistGC[3.33/4.13] Galactocentric distance (RGC)kpcpos.distancefloatTex[5/36.8] Excitation temperatureKphys.atmol.excitationfloatlog(NH2)[20.4/22.2] Log of hydrogen column densitylog(cm**-2)phys.columnDensityfloat_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.decindexedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNum[1/201] Clump number (Number)meta.idintMWISP[MWISP] Source name prefixmeta.id.part;meta.maincharSourceSource name defined by Galactic Coordinates (GDD.ddd+D.ddd)meta.id.part;meta.maincharVlsr[69.99/121.28] Central velocitykm/sphys.veloc;pos.lsrfloatdv[0.68/3.49] Linewidth (Delta_v)km/sspect.line.widthfloatMajAx[52/215] Major axis (theta_a)arcsecphys.angSizeintMinAx[65/529] Minor axis (theta_b)arcsecphys.angSizeintDiam[57/261] Diameter (theta_FWHM)arcsecphys.angSizeintPA[-94/176] Position angledegpos.posAngintReff[0.4/5.6] Effective radiuspcphys.size.radiusfloatlog(M)[1.7/4.3] Log of mass (log_Mclump)log(solMass)phys.massfloatlog(Mvir)[2.3/3.8] Log of virial masslog(solMass)phys.virialfloatavir[0.1/12.6] Virial parameter (alpha_vir)phys.mass;arith.ratiofloatlog(Sig)[1/2.8] Log of surface density (log_Sigma)log(solMass.pc**-2)phys.densityfloatlog(nH2)[2.3/4.4] Log of number density of hydrogen moleculeslog(cm**-3)phys.densityfloatdvTh[0.09/0.24] Thermal linewidth (Delta_vth)km/sspect.line.widthfloatdvNTh[0.67/3.49] Non-thermal linewidth (Delta_vnth)km/sspect.line.widthfloatFlagPotential to form massive stars (*=Yes) (Potential) (1)meta.code.errorchar_GlonPositions derived from source name (longitude part)degpos.galactic.lon_GlatPositions derived from source name (latitude part)degpos.galactic.latJ/AJ/169/291/tablea3The parameters of C^18^O clumpsdvNTh[0.3/2.63] Non-thermal linewidth (Delta_vnth)km/sspect.line.widthfloatFlagPotential to form massive stars (*=Yes) (Potential) (1)meta.code.errorchar_GlonPositions derived from source name (longitude part)degpos.galactic.lon_GlatPositions derived from source name (latitude part)degpos.galactic.lat_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.decindexedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNum[1/110] Clump number (Number)meta.idintMWISP[MWISP] Source name prefixmeta.id.part;meta.maincharSourceSource name defined by Galactic Coordinates (GDD.ddd+D.ddd)meta.id.part;meta.maincharVlsr[79.67/121] Central velocitykm/sphys.veloc;pos.lsrfloatdv[0.34/2.63] Linewidth (Delta_v)km/sspect.line.widthfloatMajAx[51/130] Major axis (theta_a)arcsecphys.angSizeintMinAx[63/220] Minor axis (theta_b)arcsecphys.angSizeintDiam[58/134] Diameter (theta_FWHM)arcsecphys.angSizeintPA[-44/157] Position angledegpos.posAngintDistHC[5.04/7.36] Heliocentric distance (Distance)kpcpos.distancefloatDistGC[3.33/4.11] Galactocentric distance (RGC)kpcpos.distancefloatTex[4.8/21.8] Excitation temperatureKphys.atmol.excitationfloatlog(NH2)[20.6/22.1] Log of hydrogen column densitylog(cm**-2)phys.columnDensityfloatReff[0.4/2.2] Effective radiuspcphys.size.radiusfloatlog(M)[1.6/3.9] Log of mass (log_Mclump)log(solMass)phys.massfloatlog(Mvir)[1.3/3.4] Log of virial masslog(solMass)phys.virialfloatavir[0.1/2.3] Virial parameter (alpha_vir)phys.mass;arith.ratiofloatlog(Sig)[1.4/2.8] Log of surface density (log_Sigma)log(solMass.pc**-2)phys.densityfloatlog(nH2)[2.9/4.6] Log of number density of hydrogen moleculeslog(cm**-3)phys.densityfloatdvTh[0.09/0.18] Thermal linewidth (Delta_vth)km/sspect.line.widthfloat