J/A+A/509/A61ivo://CDS.VizieR/J/A+A/509/A61doi:10.26093/cds/vizier.35090061CDSSaglia R.P.Fabricius M.Bender R.Montalto M.Lee C.-H.Riffeser A.,Seitz S.Morganti L.Gerhard O.Hopp U.2017-07-11T13:09:20Z2010-03-29T13:22:50ZCDS support team

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

cds-question@unistra.frgalaxiesradial-velocityline-intensitiesWe present new optical long-slit data along six position angles of the bulge region of M31. We derive accurate stellar and gas kinematics reaching 5-arcmin from the center, where the disk light contribution is always less than 30%, and out to 8-arcmin along the major axis, where the disk provides 55% of the total light. We show that the velocity dispersions of McElroy (1983ApJ...270..485M) are severely underestimated (by up to 50km/s). As a consequence, previous dynamical models have underestimated the stellar mass of M31's bulge by a factor of 2. As a further consequence, the light-weighted velocity dispersion of the galaxy grows to 166km/s and to 170km/s if rotation is also taken into account, thus reducing the discrepancy between the predicted and measured mass of the black hole at the center of M31 from a factor of 3 to a factor of 2. The kinematic position angle varies with distance, pointing to triaxiality, but a quantitative conclusion can be reached only after simultaneous proper dynamical modeling of the bulge and disk components is performed. We detect gas counter-rotation near the bulge minor axis. We measure eight emission-corrected Lick indices. They are approximately constant on circles. Using simple stellar population models we derive the age, metallicity and {alpha}-element overabundance profiles. Except for the region in the inner arcsecs of the galaxy, the bulge of M31 is uniformly old (>=12Gyr, with many best-fit ages at the model grid limit of 15Gyr), slightly {alpha}-elements overabundant ([{alpha}/Fe]~0.2) and of solar metallicity, in agreement with studies of the resolved stellar components. The predicted u-g, g-r and r-i Sloan color profiles match the dust-corrected observations reasonably well, within the known limitations of current simple stellar population models. The stellar populations have approximately radially constant mass-to-light ratios (M/L_R~4-4.5M_{sun}_/L_{sun}_ for a Kroupa IMF), which is in agreement with the stellar dynamical estimates based on our new velocity dispersions. In the inner arcsecs the luminosity-weighted age drops to 4-8Gyr, while the metallicity increases to above three times the solar value. Starting from 6-arcmin from the center along the major axis, the mean age drops to >=8Gyr with slight supersolar metallicity (~+0.1dex) and {alpha}-element overabundance (~+0.2dex) for a mass-to-light ratio M/L_R<=3M_{sun}_/L_{sun}_. Diagnostic diagrams based on the [OIII]/H{beta} and [NI]H{beta} emission line equivalent widths (EWs) ratios indicate that the gas is ionized by shocks outside 10-arcsec, but an AGN-like ionizing source could be present near the center. We speculate that a gas-rich minor merger happened some 100Myr ago, causing the observed minor axis gas counter-rotation, the recent star formation event and possibly some nuclear activity.2010A&A...509A..61Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/509/A61CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/509/A61https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/509/A61http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/509/A61https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/509/A61https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/509/A61http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/509/A61GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/509/A61/table1Log of the observationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateObservation datetime.epoch;obsnullablePAcPosition angle codemeta.code;pos.posAngcharPACorresponding position angledegpos.posAngintSeeing? FWHM of seeingarcsecinstr.obsty.seeingfloatnullableComCommentsmeta.noteJ/A+A/509/A61/spectroCombined table from original tablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRDistance from the center, positive East (G1)arcsecpos.angDistancefloatPAcPosition angle code (see Table 1) (G2)meta.code;pos.posAngcharRVStellar radial velocity, positive receiding (G3)km/sspect.dopplerVeloc;pos.heliocentricfloate_RVError on stellar radial velocitykm/sstat.errorfloatsigmaStellar velocity dispersionkm/sphys.veloc.dispersionfloate_sigmaError on stellar velocity dispersionkm/sstat.errorfloath33rd order Hermite coefficientstat.fit.paramfloate_h3Error on 3rd order Hermite coefficientstat.errorfloath44th order Hermite coefficientstat.fit.paramfloate_h4Error on 4th order Hermite coefficientstat.errorfloatVgasGas radial velocity, positive receiding (G3)km/sspect.dopplerVeloc;pos.heliocentricfloate_Vgas? Error on gas radial velocity (1)km/sstat.errorfloatnullablesgasGas velocity dispersionkm/sphys.veloc.dispersionfloate_sgas? Error on gas velocity dispersion (1)km/sstat.errorfloatnullableHbeEquivalent width (EW) of H{beta} gas emission0.1nmspect.line.eqWidth;em.line.Hbetafloate_HbeError on EW of the H{beta} gas emission0.1nmstat.errorfloatO/H? Ratio [OIII]/H{beta} of the gas emission equivalent widths (2)spect.line.intensity;arith.ratiofloatnullablee_O/H? Error on O/H (1)stat.error;phys.abundfloatnullableN/H? Ratio [NI]/H{beta} of the gas emission equivalent widths (2)spect.line.intensity;arith.ratiofloatnullablee_N/H? Error on N/H (1)stat.error;phys.abundfloatnullableHbetaH{beta} line strength0.1nmspect.line.strengthfloate_HbetaError on the H{beta} line strength0.1nmstat.errorfloatMgbMgb line strength0.1nmspect.line.strengthfloate_MgbError on the Mgb line strength0.1nmstat.errorfloatFe5015Fe5015 line strength0.1nmspect.line.strengthfloate_Fe5015Error on the Fe5015 line strength0.1nmstat.errorfloatFe5270Fe5270 line strength0.1nmspect.line.strengthfloate_Fe5270Error on the Fe5270 line strength0.1nmstat.errorfloatFe5335Fe5335 line strength0.1nmspect.line.strengthfloate_Fe5335Error on the Fe5335 line strength0.1nmstat.errorfloatFe5406Fe5406 line strength0.1nmspect.line.strengthfloate_Fe5406Error on the Fe5406 line strength0.1nmstat.errorfloatFe5709Fe5709 line strength0.1nmspect.line.strengthfloate_Fe5709Error on the Fe5709 line strength0.1nmstat.errorfloatFe5782Fe5782 line strength0.1nmspect.line.strengthfloate_Fe5782Error on the Fe5782 line strength0.1nmstat.errorfloat