J/A+A/625/A19ivo://CDS.VizieR/J/A+A/625/A19doi:10.26093/cds/vizier.36250019CDSQuerejeta M.Schinnerer E.Schruba A.Murphy E.Meidt S.Usero A.,Leroy A. K.Pety J.Bigiel F.Chevance M.Faesi C. M.Gallagher M.,Garcia-Burillo S.Glover S. C. O.Hygate A. P. S.Jimenez-Donaire M. J.,Kruijssen J. M. D.Momjian E.Rosolowsky E.Utomo D.2019-05-13T08:17:46Z2019-05-02T08:32:23ZCDS support team

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

cds-question@unistra.frgalaxiesradio-galaxiesmolecular-cloudsIt remains unclear what sets the efficiency with which molecular gas transforms into stars. Here we present a new VLA map of the spiral galaxy M51 in 33GHz radio continuum, an extinction-free tracer of star formation, at 3" scales (~100pc). We combined this map with interferometric PdBI/NOEMA observations of CO(1-0) and HCN(1-0) at matched resolution for three regions in M51 (central molecular ring, northern and southern spiral arm segments). While our measurements roughly fall on the well-known correlation between total infrared and HCN luminosity, bridging the gap between Galactic and extragalactic observations, we find systematic offsets from that relation for different dynamical environments probed in M51, e.g. the southern arm segment is more quiescent due to low star formation efficiency (SFE) of the dense gas, despite having a high dense gas fraction. Combining our results with measurements from the literature at 100pc scales, we find that the SFE of the dense gas and the dense gas fraction anti-correlate and correlate, respectively, with the local stellar mass surface density. This is consistent with previous kpc-scale studies. In addition, we find a significant anti-correlation between the SFE and velocity dispersion of the dense gas. Finally, we confirm that a correlation also holds between star formation rate surface density and the dense gas fraction, but it is not stronger than the correlation with dense gas surface density. Our results are hard to reconcile with models relying on a universal gas density threshold for star formation and suggest that turbulence and galactic dynamics play a major role in setting how efficiently dense gas converts into stars.2019A&A...625A..19Qhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/625/A19CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/568/A74 : Low-frequency (115-175MHz) image of M51 (Mulcahy+, 2014)J/A+A/592/A123 : M51 total intensity image at 333MHz (Mulcahy+, 2016)J/A+A/593/A118 : HCN(1-0) cube for the nucleus of M51 (Querejeta+, 2016)J/A+A/617/A136 : LOFAR M51 field low-frequency polarized sourceshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/625/A19https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/625/A19http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/625/A19https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/625/A19https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/625/A19http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/625/A19GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/625/A19/tablea1 (Measurements for apertures on HCN peaks)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/625/A19/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/625/A19/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/625/A19/tablea1?GETtext/xml+votable180.050000true202.456447.21080.005555555555555556Cone search capability for table J/A+A/625/A19/tablea2 (Measurements for Nyquist-sampled apertures)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/625/A19/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/625/A19/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/625/A19/tablea2?GETtext/xml+votable180.050000true202.475147.20930.005555555555555556Cone search capability for table J/A+A/625/A19/list (Information of fits datacube)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/625/A19/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/625/A19/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/625/A19/list?GETtext/xml+votable180.050000true202.4688147.194920.0055555555555555566/110272.1866029582016434e-23 2.1866029582016434e-23https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/625/A19?format=asciiRadiodefaultJ/A+A/625/A19/tablea1Measurements for apertures on HCN peaksrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameRegion in M51 (north, ring, south)meta.id;obs.fieldcharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainSigStarStellar mass surface densitysolMass.pc**-2phys.densityinte_SigStarUncertainty stellar mass surface densitysolMass.pc**-2stat.errorintTIRTotal Infrared Luminosity (TIR)1e+06solLumphys.luminosity;em.IRfloate_TIRUncertainty TIR1e+06solLumstat.errorfloatF33GHz33GHz Spectral Flux DensityuJyphot.flux.density;em.mm.30-50GHzfloate_F33GHzUncertainty 33GHz Flux DensityuJystat.errorfloattfracThermal fraction at 33GHz%phot.flux;arith.ratiofloate_tfracUncertainty thermal fraction 33GHz%stat.errorfloatSigSFRStar formation rate surface densitysolMass.Myr**-1.pc**-2phys.SFRfloate_SigSFRUncertainty SFR surface densitysolMass.Myr**-1.pc**-2stat.errorfloatIHCNHCN(1-0) intensityK.km/sphot.flux;em.radiofloate_IHCNUncertainty HCN(1-0) intensityK.km/sstat.errorfloatICO? CO(1-0) intensityK.km/sphot.flux;em.radiofloatnullablee_ICO? Uncertainty CO(1-0) intensityK.km/sstat.errorfloatnullablesigHCN? HCN(1-0) velocity dispersionkm/sinstr.dispersionfloatnullablee_sigHCN? Uncertainty HCN(1-0) velocity dispersionkm/sstat.errorfloatnullablesigCO? CO(1-0) velocity dispersionkm/sinstr.dispersionfloatnullablee_sigCO? Uncertainty CO(1-0) velocity dispersionkm/sstat.errorfloatnullableJ/A+A/625/A19/tablea2Measurements for Nyquist-sampled aperturesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameRegion in M51 (north, ring, south)meta.id;obs.fieldcharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainSigStarStellar mass surface densitysolMass.pc**-2phys.densityinte_SigStarUncertainty stellar mass surface densitysolMass.pc**-2stat.errorintTIRTotal Infrared Luminosity (TIR)1e+06solLumphys.luminosity;em.IRfloate_TIRUncertainty TIR1e+06solLumstat.errorfloatF33GHz33GHz Spectral Flux DensityuJyphot.flux.density;em.mm.30-50GHzfloate_F33GHzUncertainty 33GHz Flux DensityuJystat.errorfloattfracThermal fraction at 33GHz%phot.flux;arith.ratiofloate_tfracUncertainty thermal fraction 33GHz%stat.errorfloatSigSFRStar formation rate surface densitysolMass.Myr**-1.pc**-2phys.SFRfloate_SigSFRUncertainty SFR surface densitysolMass.Myr**-1.pc**-2stat.errorfloatIHCNHCN(1-0) intensityK.km/sphot.flux;em.radiofloate_IHCNUncertainty HCN(1-0) intensityK.km/sstat.errorfloatICO? CO(1-0) intensityK.km/sphot.flux;em.radiofloatnullablee_ICO? Uncertainty CO(1-0) intensityK.km/sstat.errorfloatnullablesigHCN? HCN(1-0) velocity dispersionkm/sinstr.dispersionfloatnullablee_sigHCN? Uncertainty HCN(1-0) velocity dispersionkm/sstat.errorfloatnullablesigCO? CO(1-0) velocity dispersionkm/sinstr.dispersionfloatnullablee_sigCO? Uncertainty CO(1-0) velocity dispersionkm/sstat.errorfloatnullableJ/A+A/625/A19/listInformation of fits datacubeNxNumber of pixels along X-axismeta.numberintrecnoRecord 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.mainNyNumber 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