J/ApJS/282/39ivo://CDS.VizieR/J/ApJS/282/39CDSJiao S.Wu J.Liu H.B.Tsai C.-W.Lin Y.Li DiZhang Z.-Y.,Cheng YuFeng L.Beuther H.Wang J.Lin L.den Brok J.Zhang L.,Xu F.Meng F.Li Z.Keenan R.P.Yu S.-Y.Yu N.Zheng Z.Liu J.,Liu Y.Ruan H.Deng F.Xiong Y.2026-08-27T07:25:57Z2026-08-27T08:24:08ZCDS support team

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

cds-question@unistra.frmillimeter-astronomysubmillimeter-astronomyinterstellar-mediumgalaxiesmolecular-cloudsco-line-emissionWe have carried out unprecedentedly deep, nearly confusion-limited JCMT SCUBA-2 mapping observations on the nearest spiral galaxy, M31 (Andromeda). The 850{mu}m image with a ~50pc resolution yields a comprehensive catalog of 383 giant molecular clouds (GMCs) that are associated with the spiral arms. In addition, it unveiled a population of 189 compact interarm GMCs in M31, which are mostly unresolved or marginally resolved. The masses of all these GMCs are in the range of 2x10^4^-6x10^6^M_{sun}_; the sizes are in the range of 30-130pc. They follow a mass-size correlation, M{propto}Rc^2.5^. The interarm GMCs are systematically less massive, more diffuse, colder, and have lower star formation efficiency (SFE) than on-arm GMCs. Moreover, within individual spatially resolved on-arm and off-arm M31 GMCs, the SFE is considerably lower than the SFE in molecular clouds in main-sequence and green valley galaxies. Follow-up investigations on M31 GMCs may provide clues for how star formation may be quenched in galactic environments. Finally, we reconstrained the dust opacity spectral index {beta} in the M31 galaxy by combining our new JCMT observations with archival Herschel and Planck data and found that the radial variation in {beta} may not be as large as has been proposed by previous studies.2026ApJS..282...39Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/282/39CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVI/139 : Herschel Observation Log (Herschel Science Centre, 2013)J/ApJ/654/240 : Giant molecular clouds in M31 (Rosolowsky+, 2007)J/ApJS/173/293 : UV-Optical galaxy color-magnitude diagram I. (Wyder+, 2007)J/A+A/487/993 : MAMBO Mapping of c2d Clouds and Cores (Kauffmann+, 2008)J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)J/ApJ/723/492 : Physical properties of GRS Mocs (Roman-Duval+, 2010)J/A+A/542/A108 : Giant molecular clouds in M33 (Gratier+, 2012)J/A+A/567/A71 : M31 Herschel images (Viaene+, 2014)J/ApJ/784/3 : The PAWS cat. of GMCs and islands in M51 (Colombo+, 2014)J/ApJ/798/58 : HELGA VI. Giant molecular cloud assoc. in M31 (Kirk+, 2015)J/A+A/590/A131 : Giant molecular filaments in the MW (Abreu-Vicente+, 2016)J/A+A/586/A50 : CMZ H2CO temperature maps (Ginsburg+, 2016)J/MNRAS/465/1789 : SCUBA-2 Cosmology Legacy Survey (Geach+, 2017)J/ApJ/834/57 : MW molecular clouds from ^12^CO (Miville-Deschenes+, 2017)J/MNRAS/477/4116 : GAMA. galaxy structure across green valley (Kelvin+, 2018)J/ApJ/862/13 : The Carnegie-Irvine Galaxy Survey. VI. Spirals (Yu+, 2018)J/MNRAS/483/4291 : Properties of JCMT CO(3-2) molecular clouds (Colombo+, 2019)J/MNRAS/493/351 : A large catalogue of molecular clouds (Chen+, 2020)J/A+A/634/A83 : THOR DR2 source list (Wang+, 2020)J/ApJS/257/43 : PHANGS-ALMA: CO(2-1) imaging of galaxies (Leroy+, 2021)J/ApJ/945/L19 : SFR & molecular gas surface densities (Sun+, 2023)J/A+A/692/A226 : Cloud matching in M33. II. (Keilmann+, 2024)http://hashtag.astro.cf.ac.uk/DR1.html : HASHTAG DR1 homepagehttp://www.esa.int/Science_Exploration/Space_Science/Planck : Planck homepagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/282/39https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/282/39http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/282/39https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/282/39https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/282/39http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/282/39GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/282/39/table2 (Physical properties of selected regions)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/282/39/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/282/39/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/282/39/table2?GETtext/xml+votable180.050000true10.251333340.61388890.0055555555555555566/2622-2623 2666 2708-2709 2752https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/282/39?format=asciiMillimeterRadiodefaultJ/ApJS/282/39/table2Physical properties of selected regionsSeq[1/572] Running sequence numbermeta.id;meta.mainintMass[0.17/59.9] Cloud mass100000solMassphys.massfloatnH[4/95.6] Gas mean volume densitycm**-3phys.densityfloatSFR[-0.0003/0.05] Star Formation RatesolMass.yr**-1.kpc**-2phys.SFRdoubleOnArmOn-arm cloud?meta.codecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[0] Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000[40/41] Degree of declination (J2000)pos.eq.dec;meta.mainArea[2974/60175] Physical areapc**2phys.areaintRc[30.7/138.4] Effective radiuspcphys.size.radiusfloatR[0.4/14.6] Annular radiuskpcphys.size.radiusfloatTdust[11.1/31.1] Dust temperatureKphys.temperaturefloatbeta[0.93/2.43] Dust opacity indexspect.indexfloatSigDust[0.09/1.7] Dust surface densitysolMass.pc**-2phot.flux.density.sbfloatSigGas[5.8/201.8] Gas surface densitysolMass.pc**-2phot.flux.density.sbfloat