J/AJ/134/321ivo://CDS.VizieR/J/AJ/134/321doi:10.26093/cds/vizier.51340321CDSProchaska L.C.Rose J.A.Caldwell N.Castilho B.V.Concannon K.,Harding P.Morrison H.Schiavon R.P.2017-12-12T14:44:55Z2009-11-04T15:22:41ZCDS support team

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

cds-question@unistra.frglobular-star-clustersspectroscopychemical-abundancesWe present a cautionary study exploring the reliability of the H{delta} line in the integrated spectra of galaxies for determining galaxy ages. Our database consists of the observed integrated spectra of ~120 early-type galaxies, 7 metal-rich globular clusters in M31 and the Galactic globular cluster 47 Tuc, and the open cluster M67. We have measured H{delta} using index definitions designed to assess contamination from the CN molecule in and around H{delta} by choosing combinations of bandpasses that both avoid and include a region of CN molecular lines redward of H{delta}. We find systematic differences in the ages derived from H{delta} measurements among the various definitions when extracting ages from H{delta} in old stellar populations with enhanced CN bands due to nonsolar abundance ratios. We propose that neighboring CN lines have a strong effect on pseudocontinuum and central bandpass levels. For stellar populations that have nonsolar abundance ratios in C and/or N, population synthesis models that do not account for abundance ratio variations cannot accurately reproduce the CN 4216{AA} band, which leads to a corresponding inaccuracy in reproducing the various H{delta} indices. Hence, caution must be used when extracting galaxy ages from the H{delta} line in old stellar populations with significant nonsolar abundance ratios.2007AJ....134..321Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/134/321CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/94/687 : Old stellar populations. V. (Worthey+, 1994)J/ApJS/111/377 : H{gamma} + H{delta} absorption features (Worthey+ 1997)J/A+A/326/1069 : Abundances in globular clusters (Russell 1997)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/134/321https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/134/321http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/134/321https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/134/321https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/134/321http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/134/321GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/134/321/table2 (Index measurements and error)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/134/321/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/134/321/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/134/321/table2?GETtext/xml+votable180.050000true6.023625-72.08127780.0055555555555555566/14 131 144 177 179 552 556 621 664 2077 2622 2623 2709 4298 4361 4447 5134 5474 6097 7287 7438 7461 7479 7560 8193 8196 8228 8515 8523 8552 8737 9446 9947 10145 10501 10520 10551 10714 10739 11791 11802 12019 17605 17612 18002 18209 18214 18269 18324 18325 18326 18830 18931 18935 18941 19442 19624 19943 19968 20014 20032 20034 20101 20181 20308 20388 23177 23208 25533 26055 26366 26457 27485 27718 27719 27721 27725 27730 27736 27738 27739 27740 27743 27763 27764 27765 27767 27772 27773 27833 27861 27862 27904 27907 27912 27913 27914 27938 27944 27947 27948 27951 28033 28037 28038 28045 28495 28517 31404 33321https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/134/321?format=asciiOpticaldefaultJ/AJ/134/321/table1Index definitionsNameIndex namemeta.noterecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIndexAbbreviated index namemeta.id;meta.maincharbp1Lower bound of central bandpass0.1nmmeta.notedoublebp2Upper bound of central bandpass0.1nmmeta.notedoublecont1Lower bound of pseudo-continuum0.1nmmeta.notedoublecont2Upper bound of pseudo-continuum0.1nmmeta.notedoubleBcont1? Lower bound of second pseudo-continuum0.1nmmeta.notedoublenullableBcont2? Upper bound of second pseudo-continuum0.1nmmeta.notedoublenullableRef[ab] Reference of index (1)meta.ref;spect.indexcharJ/AJ/134/321/table2Index measurements and errorrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTypeSource location (1)meta.codecharNameSource namemeta.id;meta.maincharHdAbH{delta}_A_b index (2)spect.index;em.line.Hbetafloate_HdAb1{sigma} error in hdAbstat.errorfloatHdAH{delta}_A_ index (2)spect.index;em.line.Hbetafloate_HdA1{sigma} error in HdAstat.errorfloatHdArH{delta}_A_r index (2)spect.index;em.line.Hbetafloate_HdAr1{sigma} error in HdArstat.errorfloatHdFbH{delta}_F_b index (2)spect.index;em.line.Hbetafloate_HdFb1{sigma} error in HdFbstat.errorfloatHdFH{delta}_F_ index (2)spect.index;em.line.Hbetafloate_HdF1{sigma} error in HdFstat.errorfloatHdFrH{delta}_F_r index (2)spect.index;em.line.Hbetafloate_HdFr1{sigma} error in HdFrstat.errorfloatHbbH{beta}_b_ index (2)spect.index;em.line.Hbetafloate_Hbb1{sigma} error in Hbbstat.errorfloatHbH{beta} index (2)spect.index;em.line.Hbetafloate_Hb1{sigma} error in Hbstat.errorfloatHbrH{beta}_r_ index (2)spect.index;em.line.Hbetafloate_Hbr1{sigma} error in Hbrstat.errorfloatFe4383Fe4383 index (2)spect.index;em.line.Hbetafloate_Fe43831{sigma} error in Fe4383stat.errorfloatSimbadNameSimbad column added by the CDSmeta.idchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main