J/MNRAS/448/2687ivo://CDS.VizieR/J/MNRAS/448/2687doi:10.26093/cds/vizier.74482687CDSJames B.L.Koposov S.Stark D.P.Belokurov V.Pettini M.,Olszewski E.W.2024-08-14T20:20:17Z2017-12-05T07:29:02ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopyExtremely metal poor (XMP) galaxies are known to be very rare, despite the large numbers of low-mass galaxies predicted by the local galaxy luminosity function. This paper presents a subsample of galaxies that were selected via a morphology-based search on Sloan Digital Sky Survey images with the aim of finding these elusive XMP galaxies. By using the recently discovered XMP galaxy, Leo P, as a guide, we obtained a collection of faint, blue systems, each with isolated H II regions embedded in a diffuse continuum, that have remained optically undetected until now. Here we show the first results from optical spectroscopic follow-up observations of 12 of ~100 of these blue diffuse dwarf (BDD) galaxies yielded by our search algorithm. Oxygen abundances were obtained via the direct method for eight galaxies, and found to be in the range 7.45<12+log(O/H)<8.0, with two galaxies being classified as XMPs. All BDDs were found to currently have a young star-forming population (<10 Myr) and relatively high ionization parameters of their H II regions. Despite their low luminosities (-11<~M_B_<~-18) and low surface brightnesses (~23-25 mag/arcsec^2^), the galaxies were found to be actively star forming, with current star formation rates between 0.0003 and 0.078 M_{sun}_/yr. From our current subsample, BDD galaxies appear to be a population of non-quiescent dwarf irregular galaxies, or the diffuse counterparts to blue compact galaxies and as such may bridge the gap between these two populations. Our search algorithm demonstrates that morphology-based searches are successful in uncovering more diffuse metal-poor star-forming galaxies, which traditional emission-line-based searches overlook.2015MNRAS.448.2687Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/448/2687CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/139 : The SDSS Photometric Catalog, Release 9J/A+A/546/A122 : SDSS extremely metal-poor emission-line galaxiesJ/A+A/558/A18 : HI spectra of extremely metal-poor (XMP) galaxiesJ/ApJ/819/110 : Extremely metal-poor (XMP) galaxies in SDSS. II.https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/448/2687https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/448/2687http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/448/2687https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/448/2687https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/448/2687http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/448/2687GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/448/2687/galaxy (BDDs galaxies sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/448/2687/galaxy?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/448/2687/galaxy?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/448/2687/galaxy?GETtext/xml+votable180.050000true241.973559.117711110.0055555555555555566/8717 31631https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/448/2687?format=asciiOpticaldefaultJ/MNRAS/448/2687/galaxyBDDs galaxies samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameObject identifier (KJN) (1)meta.id;meta.maincharSDSSSDSS identifier (JHHMMSS.ss+DDMMSS.s)meta.idcharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainTarget1Target region name in tablea1.dat (KJN.N) (2)meta.idcharTarget2Target region name in tablea1.dat (KJN.N) (2)meta.idcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/MNRAS/448/2687/tablea1Spectroscopic line fluxes and dereddened line intensities as measured from the spectra shown in Fig. 2.recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLineDetected emission linemeta.id;spect.linecharn_Line[abcd] Note on line (1)meta.notecharlambda? Wavelength ({AA})0.1nmem.wlfloatnullablel_SKJ1.0[<] Limit flag on SKJ1.0meta.code.errorcharSKJ1.0? KJ1.0 integrated line flux (2)spect.line.intensity;arith.ratiofloatnullablee_SKJ1.0? Uncertainty in SKJ1.0 (2)stat.errorfloatnullablen_SKJ1.0[efgh] Note on SKJ1.0 (3)meta.notecharl_IKJ1.0[<] Limit flag on IKJ1.0meta.code.errorcharIKJ1.0? IKJ1.0 dereddened line intensity (2)spect.line.intensity;arith.ratiofloatnullablee_IKJ1.0? Uncertainty in IKJ1.0 (2)stat.errorfloatnullablen_IKJ1.0[ijkl] Note on IKJ1.0 (4)meta.notecharSKJ1.1? SKJ1.1 integrated line flux (2)spect.line.intensity;arith.ratiofloatnullablee_SKJ1.1? Uncertainty in SKJ1.1 (2)stat.errorfloatnullablen_SKJ1.1[mnop] Note on SKJ1.1 (5)meta.notecharIKJ1.1? IKJ1.1 dereddened line intensity (2)spect.line.intensity;arith.ratiofloatnullablee_IKJ1.1? Uncertainty in IKJ1.1 (2)stat.errorfloatnullablen_IKJ1.1[qrst] Note on IKJ1.1 (6)meta.notecharl_SKJ3.0[<] Limit flag on SKJ3.0meta.code.errorcharSKJ3.0? SKJ3.0 integrated line flux (2)spect.line.intensity;arith.ratiofloatnullablee_SKJ3.0? Uncertainty in SKJ3.0 (2)stat.errorfloatnullablen_SKJ3.0[uvwx] Note on SKJ3.0 (7)meta.notecharl_IKJ3.0[<] Limit flag on IKJ3.0meta.code.errorcharIKJ3.0? IKJ3.0 dereddened line intensity (2)spect.line.intensity;arith.ratiofloatnullablee_IKJ3.0? Uncertainty in IKJ3.0 (2)stat.errorfloatnullablen_IKJ3.0[y z a'b'] Note on IKJ3.0 (8)meta.notecharl_SKJ3.1[<] Limit flag on SKJ3.1meta.code.errorcharSKJ3.1? SKJ3.1 integrated line flux (2)spect.line.intensity;arith.ratiofloatnullablee_SKJ3.1? Uncertainty in SKJ3.1 (2)stat.errorfloatnullablen_SKJ3.1[c'd'e'] Note on SKJ3.1 (9)meta.notecharl_IKJ3.1[<] Limit flag on IKJ3.1meta.code.errorcharIKJ3.1? IKJ3.1 dereddened line intensity (2)spect.line.intensity;arith.ratiofloatnullablee_IKJ3.1? Uncertainty in IKJ3.1 (2)stat.errorfloatnullablen_IKJ3.1[f'g'h'] Note on IKJ3.1 (10)meta.notechar