J/MNRAS/485/1085ivo://CDS.VizieR/J/MNRAS/485/1085doi:10.26093/cds/vizier.74851085CDSStampoulis V.van Dyk D.A.Kashyap V.L.Zezas A.2024-08-19T20:17:06Z2023-09-08T09:17:29ZCDS support team

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

cds-question@unistra.frgalaxy-clustersgalaxiescatalogsspectroscopyvisible-astronomyWe propose a new soft clustering scheme for classifying galaxies in different activity classes using simultaneously four emission-line ratios: log([NII]/H{alpha}), log([SII]/H{alpha}), log([OI]/H{alpha}), and log([OIII]/H{beta}). We fit 20 multivariate Gaussian distributions to the four-dimensional distribution of these lines obtained from the Sloan Digital Sky Survey in order to capture local structures and subsequently group the multivariate Gaussian distributions to represent the complex multidimensional structure of the joint distribution of galaxy spectra in the four-dimensional line ratio space. The main advantages of this method are the use of all four optical-line ratios simultaneously and the adoption of a clustering scheme. This maximizes the use of the available information, avoids contradicting classifications, and treats each class as a distribution resulting in soft classification boundaries and providing the probability for an object to belong to each class. We also introduce linear multidimensional decision surfaces using support vector machines based on the classification of our soft clustering scheme. This linear multidimensional hard clustering technique shows high classification accuracy with respect to our soft clustering scheme.2019MNRAS.485.1085Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/485/1085CatalogResearchIsServedByTAP VizieR generic servicerelated-tohttps://skyserver.sdss.org/dr8 : SDSS DR8 Home Pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/485/1085https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/485/1085http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/485/1085https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/485/1085https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/485/1085http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/485/1085GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/MNRAS/485/1085/table2Activity classification of the emission-line galaxies in the SDSS-DR8 based on SoDDA[OI]/HaLogarithm of the [OI]/H{alpha} emission line ratiophot.flux;arith.ratiodouble[OIII]/HbLogarithm of the [OIII]/H{beta} emission line ratiophot.flux;arith.ratiodoublePSFGProbability that a galaxy belongs to the SFG class based on the SoDDA analysismeta.code.class;stat.probabilitydoublePSeyfertProbability that a galaxy belongs to the Seyfert class based on the SoDDA analysismeta.code.class;stat.probabilitydoublePLINERProbability that a galaxy belongs to the LINER class based on the SoDDA analysismeta.code.class;stat.probabilitydoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSloanDisplay the SDSS data for this objectmeta.ref.urlcharIDSDSS DR8 SpecObjIDmeta.id;meta.mainIndexInternal object identifiermeta.idint[NII]/HaLogarithm of the [NII]/H{alpha} emission line ratiophot.flux;arith.ratiodouble[SII]/HaLogarithm of the [SII]/H{alpha} emission line ratiophot.flux;arith.ratiodoublePCompositeProbability that a galaxy belongs to the composite class based on the SoDDA analysismeta.code.class;stat.probabilitydoubleClass[0/3] Highest-ranking activity class (1)meta.codeint