J/ApJ/770/137ivo://CDS.VizieR/J/ApJ/770/137doi:10.26093/cds/vizier.17700137CDSFord H.A.Bregman J.N.2015-02-27T07:42:33Z2015-02-03T13:13:44ZCDS support team

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

cds-question@unistra.frgalaxiesultraviolet-photometrySmall amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical "red and dead" NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8x10^-5^M_{sun}_/yr. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5)x10^-4^M_{sun}_/yr), but decreased by a factor of several in the past 0.3Gyr. Most star clusters have a mass between 10^2^ and 10^4^M_{sun}_. The specific star formation rates of ~10^-16^/yr (at the present day) or ~10^-14^/yr (when averaging over the past Gyr) imply that a fraction 10^-8^ of the stellar mass is younger than 100Myr and 10^-5^ is younger than 1Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect.2013ApJ...770..137Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/770/137CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)J/ApJ/768/137 : Color-metallicity relations. IV. M84 GCs (Yoon+, 2013)J/ApJ/759/116 : Chemical analysis of NGC 4636 globular clusters (Park+, 2012)J/A+A/544/A115 : Velocities of NGC 4636 globular clusters (Schuberth+, 2012)J/A+A/438/1163 : Catalogue of Open Cluster Data (COCD) (Kharchenko+, 2005)J/A+A/433/43 : C-T1 phot. of NGC 4636 GC system (Dirsch+, 2005)J/AJ/129/2138 : Centers of early-type galaxies with HST (Lauer+, 2005)J/MNRAS/363/769 : Dynamical modelling of 4 early-type gal. (Samurovic+, 2005)J/MNRAS/345/949 : UBRI photometry of NGC 3379 GCs (Whitlock+, 2003)J/ApJS/127/39 : Stellar & gas kinematics in early-type galaxies (Caon+ 2000)J/A+AS/96/269 : Stellar Models from 0.8 to 120 Msolar (Schaller+, 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/770/137https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/770/137http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/770/137https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/770/137https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/770/137http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/770/137GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/770/137/table2 (Properties of UV-bright clusters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/770/137/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/770/137/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/770/137/table2?GETtext/xml+votable180.050000true161.9294916712.589052780.0055555555555555566/26125 26313 27515 277735.4699463256110985e-19 9.254243743779334e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/770/137?format=asciiUVdefaultJ/ApJ/770/137/table2Properties of UV-bright clustersSeq[1/271] Cluster ID numbermeta.idintprimaryNameHost galaxy NCG name (3379, 4697, 4636 or 4374)meta.id;meta.mainintRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainF225W[21.9/25.6] HST/WFC3 F225W band magnitudemagphot.mag;em.UV.200-300nmfloate_F225W[0.02/0.4] Uncertainty in F225Wmagmagstat.errorfloatF336W[21/26.2] HST/WFC3 F336W band magnitudemagphot.mag;em.opt.Ufloate_F336WUncertainty in F336Wmagmagstat.errorfloatcol[-2.3/1] The (F225W-F336W) color indexmagphot.color;em.UVfloate_colUncertainty in colormagstat.errorfloatMass[100/30000]? Cluster masssolMassphys.massdoublenullableE_Mass[0/15900]? Upper uncertainty in MasssolMassstat.error;stat.maxdoublenullablee_Mass[0/19200]? Lower uncertainty in MasssolMassstat.error;phys.massdoublenullableAge? Cluster ageyrtime.agedoublenullableE_Age? Upper uncertainty in Ageyrstat.error;stat.maxdoublenullablee_Age? Lower uncertainty in Ageyrstat.error;time.agedoublenullable