J/ApJ/853/114ivo://CDS.VizieR/J/ApJ/853/114doi:10.26093/cds/vizier.18530114CDSEigenbrot A.Bershady M.A.2019-01-09T13:57:52Z2018-12-04T07:40:39ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopyvisible-astronomyWe have measured vertical and radial stellar population gradients in NGC 891. We compare these gradients to those known for the Milky Way from studies of resolved stars. Optical spectroscopic measurements extend spatially from the disk midplane up to 2.6kpc in height and out to a radius of 12kpc on both sides of the galaxy. Data were acquired with {nabla}Pak, a variable-pitch fiber integral field unit (IFU) on the WIYN telescope. We describe the laboratory and on-sky performance of {nabla}Pak, as well as modifications to the standard observational and analysis procedures necessary to calibrate data taken with this unique IFU. {nabla}Pak has a mean throughput of 80% at 5500{AA}. To achieve an estimated precision of 10% in light-weighted mean age and metallicity, we define a set of spatial apertures in radius and height in which spectra are binned to achieve a signal-to-noise ratio of ~20{AA}^-1^. We use spectral indices to measure age, metallicity, and abundance, indicating that NGC 891's stellar populations have 0.2<Z/Z_{sun}_<1 and +0.2dex {alpha}-enhancement on average. We find a clear transition from young (<3-5Gyr) to old (>7Gyr) stellar populations at 0.4kpc, roughly the scale height of the thin disk. We also find a slight trend toward younger populations at larger radii, consistent with flaring in an inside-out disk formation scenario. The vertical age gradient in NGC 891 is in remarkable qualitative agreement with a model for disk heating tuned to studies of the Milk Way's solar cylinder.2018ApJ...853..114Ehttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/853/114CatalogResearchIsServedByTAP VizieR generic servicerelated-toIII/211 : Keck/HIRES Sky Line Atlas (Osterbrock+ 1997)III/232 : STELIB: library of R~2000 stellar spectra (Le Borgne+, 2003)J/ApJS/111/377 : H{gamma} & H{delta} absorption features (Worthey+ 1997)J/MNRAS/371/703 : MILES library of empirical spectra (Sanchez-Blazquez+, 2006)J/ApJ/653/1027 : TKRS/GOODS-N Field galaxies (Weiner+, 2006)J/MNRAS/386/715 : Absorption-line strengths in Coma galaxies (Trager+, 2008)J/MNRAS/396/1231 : Astrophotometric catalogue of NGC 891 (Rejkuba+, 2009)J/ApJ/706/1364 : SINS survey of high-z galaxies (Forster Schreiber+, 2009)J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)J/A+A/565/A4 : NGC 891 70-500um images (Hughes+, 2014)J/A+A/575/A17 : NGC 891 Herschel PACS and SPIRE spectroscopy (Hughes+, 2015)J/A+A/581/A103 : CALIFA survey across the Hubble sequence (Gonzalez+, 2015)J/ApJS/219/15 : Morphologies of z=0-10 galaxies with HST (Shibuya+, 2015)J/ApJ/832/118 : Emission-line spectroscopy in NGC 891 (Boettcher+, 2016)J/ApJ/823/114 : The Cannon: a new approach to determine masses (Ness+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/853/114https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/853/114http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/853/114https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/853/114https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/853/114http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/853/114GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/853/114/table5Data aperturesP[1/6] Pointingmeta.id;obsintCore[200/600] Fiber core diameteruminstr.setupintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAp[1/60] Apertureinstr.setupintN[1/15] Number of individual fibers in aperturemeta.numberintFiberFiber ID's in aperture; comma-separatedmeta.id;phys.angSize;instr.fovcharSNR[13.7/108] Signal-to-noisestat.snrfloatrproj[-11/9] Projected radiuskpcpos.distancefloatZ[-0.3/2.4] Height above midplanekpcpos.cartesian.z;pos.galacticfloatFlagQuality flag (g=high-quality spectra) (1)meta.code.errorcharJ/ApJ/853/114/table6Velocity and radial dataP[1/6] Pointingmeta.id;obsintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAp[1/60] Apertureinstr.setupintVHaNS[-960/1316]? Nebular emission velocitykm/sphys.velocfloatnullablee_VHaNS[24/315]? Uncertainty in VHaNSkm/sstat.errorfloatnullableV*c[129/1393] Corrected stellar velocitykm/sphys.velocfloatVLOS[-416/1354] "Observed" line-of-sight velocitykm/sphys.velocfloate_VLOS[24.5/554] Uncertainty in VLOSkm/sstat.errorfloatr[0.3/112] Galactic radiuskpcphys.size.radius;pos.galacticfloate_r[0.1/2449] Uncertainty in rkpcstat.errorfloatJ/ApJ/853/114/table8NGC 891 index measurementsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintP[1/6] Pointingmeta.id;obsintAp[1/60] Apertureinstr.setupintDn4000[0.9/2.4] The 4000 Angstrom breakspect.indexfloate_Dn4000[0.01/0.1] Uncertainty in Dn4000stat.errorfloatHdA[-2.1/8] The H-delta index; Angstroms0.1nmspect.indexfloate_HdA[0.2/2.6] Uncertainty in HdA0.1nmstat.errorfloatMgb[0.03/4.3] The Mgb index; Angstroms0.1nmmeta.code;spect.indexfloate_Mgb[0.1/1.1] Uncerainty in Mgb0.1nmstat.errorfloat<Fe>[-0.3/2.7] Composite Iron index; Angstroms0.1nmmeta.code;spect.indexfloate_<Fe>[0.1/0.9] Uncertainty in <Fe>0.1nmstat.error;phys.abund.Fefloat[MgFe][0.2/2.8]? The Magnesium/Iron index; Angstroms0.1nmspect.indexfloatnullablee_[MgFe][0.1/1.8]? Uncertainty in [MgFe]0.1nmstat.errorfloatnullableJ/ApJ/853/114/table9{nabla}Pak fiber locations and lab dataT4.4[0.4/0.9] Output flux within f/4.4 (1)phot.flux;arith.ratiofloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFiber[1/109] Fiber numbermeta.id;meta.mainintoRA[-33.1/66.5] Offset distance in RA from fiber 105arcsecpos.eq.ra;arith.difffloatoDE[-51.5/50] Offset distance in DEC from fiber 105arcsecpos.eq.dec;arith.difffloatDiam[1.8/5.7] Fiber on-sky diameterarcsecphys.angSizefloatTtot[0.7/0.9] Total throughputphot.flux;arith.ratiofloatT4[0.5/0.9] Output flux within f/4 (1)phot.flux;arith.ratiofloatT5[0.3/0.9] Output flux within f/5 (1)phot.flux;arith.ratiofloatLFRD[0.04/0.3] FRD-induced throughput lossphot.flux;arith.ratiofloat