J/MNRAS/468/3965ivo://CDS.VizieR/J/MNRAS/468/3965doi:10.26093/cds/vizier.74683965CDSFederrath C.Salim D.M.Medling A.M.Davies R.L.Yuan T.Bian F.,Groves B.A.Ho I.-T.Sharp R.Kewley L.J.Sweet S.M.Richards S.N.,Bryant J.J.Brough S.Croom S.Scott N.Lawrence J.,Konstantopoulos I.Goodwin M.2024-08-17T20:18:47Z2020-04-15T09:34:01ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleistar-forming-regionsgalaxy-classification-systemsStars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H_2_) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H_2_, but CO is much less abundant and the conversion from CO intensity to H_2_ mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas ({Sigma}_gas_) using optical spectroscopy. We utilize the spatially resolved H{alpha} maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of {Sigma}_gas_ by inverting the multi-freefall star formation relation, which connects the star formation rate surface density ({Sigma}_SFR_) with {Sigma}_gas_ and the turbulent Mach number (M). Based on the measured range of {Sigma}_SFR_=0.005-1.5M_{sun}_/yr/kpc^2^ and M=18-130, we predict {Sigma}_gas_=7-200M_{sun}_/pc^2^ in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured {Sigma}_gas_ obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as 'star-forming' (219) or 'composite/AGN/shock' (41), and find that in 'composite/AGN/shock' galaxies the average {Sigma}_SFR_, M and {Sigma}_gas_ are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of {Sigma}_gas_ with those obtained by inverting the Kennicutt-Schmidt relation and find that our new method is a factor of 2 more accurate in predicting {Sigma}_gas_, with an average deviation of 32 per cent from the actual {Sigma}_gas_.2017MNRAS.468.3965Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/468/3965CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/452/2087 : Galaxy And Mass Assembly (GAMA): DR2 (Liske+, 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/468/3965https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/468/3965http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/468/3965https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/468/3965https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/468/3965http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/468/3965GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/468/3965/tablea1a (Spaxel-averaged physical parameters required to derive an estimate of the molecular gas surface density {Sigma}_gas_, star-forming classified galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/468/3965/tablea1a?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/468/3965/tablea1a?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/468/3965/tablea1a?GETtext/xml+votable180.050000true182.016480.69760.005555555555555556Cone search capability for table J/MNRAS/468/3965/tablea1b (Spaxel-averaged physical parameters required to derive an estimate of the molecular gas surface density {Sigma}_gas_, composite/AGN/shock classified galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/468/3965/tablea1b?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/468/3965/tablea1b?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/468/3965/tablea1b?GETtext/xml+votable180.050000true176.359550.004020.0055555555555555565/5469 6484 6489 6491 6571 6740 6742 6/4096 4098-4099 4101-4102 4104 4106-4107 4112 21845-21847 21852-21853 21855 21872-21874 25596-25598 25915 25918 25931 25942-25943 25952-25954 25962-25963 25968 26001 26004 26048-26049 26051 26054 26057 26254 26275-26277 26281 26288-26289 26291 26951 26957 26959 26965 26973 27278-27279 27300-27301 27303 27312 27314-27315 27318 27321-27322 27324 27650 27652 27656https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/468/3965?format=asciiOpticaldefaultJ/MNRAS/468/3965/tablea1aSpaxel-averaged physical parameters required to derive an estimate of the molecular gas surface density {Sigma}_gas_, star-forming classified galaxieszRedshiftsrc.redshiftfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGAMAGAMA identification numbermeta.id;meta.mainintepsEllipticitysrc.ellipticityfloatNspaxNumber of valid spaxels for gas column density estimatemeta.numberintLspaxLinear size of each spaxelpcphys.size.diameterintSSFRSpaxel-averaged {Sigma}SFRsolMass.yr**-1.kpc**-2phys.SFRfloate_SSFRrms uncertainty on SSFRsolMass.yr**-1.kpc**-2stat.errorfloatMSpaxel-averaged turbulent Mach numberphys.veloc;arith.diffinte_Mrms uncertainty on Mstat.errorintrhoSpaxel-averaged gas volume density1e-24g.cm**-3meta.bib.volumefloate_rhorms uncertainty on rho1e-24g.cm**-3stat.errorfloattffSpaxel-averaged local freefall timeMyrtime.epochfloate_tffrms uncertainty on tffMyrstat.errorfloatSgas/tmSpaxel-averaged multi-freefall gas consumption rate, ({Sigma}_gas_/t)_multi-ff_solMass.yr**-1.kpc**-2phys.SFRfloate_Sgas/tmrms uncertainty on Sgas/tmsolMass.yr**-1.kpc**-2stat.errorfloatSgas/tsSpaxel-averaged single-freefall gas consumption rate, ({Sigma}_gas_/t)_single-ff_solMass.yr**-1.kpc**-2phys.SFRfloate_Sgas/tsrms uncertainty on Sgas/tssolMass.yr**-1.kpc**-2stat.errorfloatSgasSpaxel-averaged molecular gas surface density, {Sigma}_gas_solMass.pc**-2phot.flux.density.sbfloate_Sgasrms uncertainty on SgassolMass.pc**-2stat.errorfloatSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from J/MNRAS/452/2087/inputcatdegpos.eq.ra;meta.main_DEDeclination (J2000) from J/MNRAS/452/2087/inputcatdegpos.eq.dec;meta.mainJ/MNRAS/468/3965/tablea1bSpaxel-averaged physical parameters required to derive an estimate of the molecular gas surface density {Sigma}_gas_, composite/AGN/shock classified galaxiesMSpaxel-averaged turbulent Mach numberphys.veloc;arith.diffintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGAMAGAMA identification numbermeta.id;meta.mainintzRedshiftsrc.redshiftfloatepsEllipticitysrc.ellipticityfloatNspaxNumber of valid spaxels for gas column density estimatemeta.numberintLspaxLinear size of each spaxelpcphys.size.diameterintSSFRSpaxel-averaged {Sigma}SFRsolMass.yr**-1.kpc**-2phys.SFRfloate_SSFRrms uncertainty on SSFRsolMass.yr**-1.kpc**-2stat.errorfloate_Mrms uncertainty on Mstat.errorintrhoSpaxel-averaged gas volume density1e-24g.cm**-3meta.bib.volumefloate_rhorms uncertainty on rho1e-24g.cm**-3stat.errorfloattffSpaxel-averaged local freefall timeMyrtime.epochfloate_tffrms uncertainty on tffMyrstat.errorfloatSgas/tmSpaxel-averaged multi-freefall gas consumption rate, ({Sigma}_gas_/t)_multi-ff_solMass.yr**-1.kpc**-2phys.SFRfloate_Sgas/tmrms uncertainty on Sgas/tmsolMass.yr**-1.kpc**-2stat.errorfloatSgas/tsSpaxel-averaged single-freefall gas consumption rate, ({Sigma}_gas_/t)_single-ff_solMass.yr**-1.kpc**-2phys.SFRfloate_Sgas/tsrms uncertainty on Sgas/tssolMass.yr**-1.kpc**-2stat.errorfloatSgasSpaxel-averaged molecular gas surface density, {Sigma}_gas_solMass.pc**-2phot.flux.density.sbfloate_Sgasrms uncertainty on SgassolMass.pc**-2stat.errorfloatSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from J/MNRAS/452/2087/inputcatdegpos.eq.ra;meta.main_DEDeclination (J2000) from J/MNRAS/452/2087/inputcatdegpos.eq.dec;meta.main