J/A+A/649/A53ivo://CDS.VizieR/J/A+A/649/A53doi:10.26093/cds/vizier.36490053CDSFraix-Burnet D.Bouveyron C.Moultaka J.2021-09-17T07:23:28Z2021-05-14T07:59:56ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopystellar-spectral-typesDefining templates of galaxy spectra is useful to quickly characterise new obervations and organise data bases from surveys. These templates are usually built from a pre-defined classification based on other criteria. We present an unsupervised classification of 702248 spectra of galaxies and quasars with redshifts smaller than 0.25 that were retrieved from the Sloan Digital Sky Survey (SDSS) database, release 7. The spectra were first corrected for the redshift, then wavelet-filtered to reduce the noise, and finally binned to obtain about 1437 wavelengths per spectrum. Fisher-EM, an unsupervised clustering discriminative latent mixture model algorithm, was applied on these corrected spectra, considering the full set as well as several subsets of 100000 and 300000 spectra. The optimum number of classes given by a penalised likelihood criterion is 86 classes, the 37 most populated ones gathering 99% of the sample. These classes are established from a subset of 302214 spectra. Using several cross-validation techniques we find that this classification is in agreement with the results obtained on the other subsets with an average misclassification error of about 15\%. The large number of very small classes tends to increase this error rate. In this paper, we make a first quick comparison of our classes with the templates of Kennicutt (1992), Dobos et al (2012), Wang et al (2018). This is the first time that an automatic, objective and robust unsupervised classification is established on such a large amount of spectra of galaxies. The mean spectra of the classes can be used as templates for a large majority of galaxies in our Universe.2021A&A...649A..53Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/649/A53CatalogResearchIsServedByTAP VizieR generic servicerelated-tohttp://skyserver.sdss.org/dr7 : SDSS DR7 Home Pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/649/A53https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/649/A53http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/649/A53https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/649/A53https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/649/A53http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/649/A53GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/649/A53/meansk86Mean spectra of the 86 classesA5Mean spectra of class A5phot.fluxdoubleA18Mean spectra of class A18phot.fluxdoubleA15Mean spectra of class A15phot.fluxdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength (Angstroem)0.1nmem.wldoubleA8Mean spectra of class A8phot.fluxdoubleA16Mean spectra of class A16phot.fluxdoubleA22Mean spectra of class A22phot.fluxdoubleA35Mean spectra of class A35phot.fluxdoubleA21Mean spectra of class A21phot.fluxdoubleA30Mean spectra of class A30phot.fluxdoubleA23Mean spectra of class A23phot.fluxdoubleA25Mean spectra of class A25phot.fluxdoubleA38Mean spectra of class A38phot.fluxdoubleA4Mean spectra of class A4phot.fluxdoubleA29Mean spectra of class A29phot.fluxdoubleA7Mean spectra of class A7phot.fluxdoubleA43Mean spectra of class A43phot.fluxdoubleA11Mean spectra of class A11phot.fluxdoubleA3Mean spectra of class A3phot.fluxdoubleA36Mean spectra of class A36phot.fluxdoubleA50Mean spectra of class A50phot.fluxdoubleA37Mean spectra of class A37phot.fluxdoubleA28Mean spectra of class A28phot.fluxdoubleA6Mean spectra of class A6phot.fluxdoubleA39Mean spectra of class A39phot.fluxdoubleA2Mean spectra of class A2phot.fluxdoubleA20Mean spectra of class A20phot.fluxdoubleA45Mean spectra of class A45phot.fluxdoubleA46Mean spectra of class A46phot.fluxdoubleA26Mean spectra of class A26phot.fluxdoubleA47Mean spectra of class A47phot.fluxdoubleA32Mean spectra of class A32phot.fluxdoubleA10Mean spectra of class A10phot.fluxdoubleA17Mean spectra of class A17phot.fluxdoubleA48Mean spectra of class A48phot.fluxdoubleA13Mean spectra of class A13phot.fluxdoubleA44Mean spectra of class A44phot.fluxdoubleA9Mean spectra of class A9phot.fluxdoubleA49Mean spectra of class A49phot.fluxdoubleA40Mean spectra of class A40phot.fluxdoubleA34Mean spectra of class A34phot.fluxdoubleA19Mean spectra of class A19phot.fluxdoubleA31Mean spectra of class A31phot.fluxdoubleA33Mean spectra of class A33phot.fluxdoubleA41Mean spectra of class A41phot.fluxdoubleA27Mean spectra of class A27phot.fluxdoubleA24Mean spectra of class A24phot.fluxdoubleA12Mean spectra of class A12phot.fluxdoubleA42Mean spectra of class A42phot.fluxdoubleA1Mean spectra of class A1phot.fluxdoubleA14Mean spectra of class A14phot.fluxdoubleB12Mean spectra of class B12phot.fluxdoubleB20Mean spectra of class B20phot.fluxdoubleB7Mean spectra of class B7phot.fluxdoubleB19Mean spectra of class B19phot.fluxdoubleB14Mean spectra of class B14phot.fluxdoubleB6Mean spectra of class B6phot.fluxdoubleB24Mean spectra of class B24phot.fluxdoubleB5Mean spectra of class B5phot.fluxdoubleB21Mean spectra of class B21phot.fluxdoubleB1Mean spectra of class B1phot.fluxdoubleB16Mean spectra of class B16phot.fluxdoubleB2Mean spectra of class B2phot.fluxdoubleB13Mean spectra of class B13phot.fluxdoubleB17Mean spectra of class B17phot.fluxdoubleB8Mean spectra of class B8phot.fluxdoubleB23Mean spectra of class B23phot.fluxdoubleB15Mean spectra of class B15phot.fluxdoubleB3Mean spectra of class B3phot.fluxdoubleB4Mean spectra of class B4phot.fluxdoubleB25Mean spectra of class B25phot.fluxdoubleB10Mean spectra of class B10phot.fluxdoubleB9Mean spectra of class B9phot.fluxdoubleB22Mean spectra of class B22phot.fluxdoubleB18Mean spectra of class B18phot.fluxdoubleB11Mean spectra of class B11phot.fluxdoubleC9Mean spectra of class C9phot.fluxdoubleC7Mean spectra of class C7phot.fluxdoubleC10Mean spectra of class C10phot.fluxdoubleC1Mean spectra of class C1phot.fluxdoubleC3Mean spectra of class C3phot.fluxdoubleC6Mean spectra of class C6phot.fluxdoubleC5Mean spectra of class C5phot.fluxdoubleC8Mean spectra of class C8phot.fluxdoubleC2Mean spectra of class C2phot.fluxdoubleC4Mean spectra of class C4phot.fluxdoubleDMean spectra of class Dphot.fluxdoubleJ/A+A/649/A53/classk86Classes K86 of 302248 spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintspecObjIDThe SDSS index of the spectrummeta.idFEMK86classThe class of each spectrum (1)meta.code.classcharSDSSDisplay the SDSS spectrummeta.ref.urlcharJ/A+A/649/A53/tablec1*Correspondence between our classes (Fisher-EM) and those of other atlasesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClassFisher-EM class (this paper) (1)meta.code.classcharK92Kennicutt (1992ApJS...79..255K, Cat. VII/141) classmeta.code.classcharD12Dobos et al. (2012MNRAS.420.1217D) class (2)meta.code.classcharW18Wang et al. (2018MNRAS.474.1873W, Cat. J/MNRAS/474/1873) classmeta.code.classchar