J/ApJ/819/110ivo://CDS.VizieR/J/ApJ/819/110doi:10.26093/cds/vizier.18190110CDSSanchez Almeida J.Perez-Montero E.Morales-Luis A.B.Munoz-Tunon C.,Garcia-Benito R.Nuza S.E.Kitaura F.S.2023-08-16T12:44:54Z2016-06-21T13:26:24ZCDS support team

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

cds-question@unistra.frchemical-abundancesgalaxiesspectroscopyExtremely metal-poor (XMP) galaxies are defined to have a gas-phase metallicity smaller than a tenth of the solar value (12+log[O/H]<7.69). They are uncommon, chemically and possibly dynamically primitive, with physical conditions characteristic of earlier phases of the universe. We search for new XMPs in the Sloan Digital Sky Survey (SDSS) in a work that complements Paper I (Morales-Luis+, 2011, J/ApJ/743/77). This time, high electron temperature objects are selected; metals are a main coolant of the gas, so metal-poor objects contain high-temperature gas. Using the algorithm k-means, we classify 788677 spectra to select 1281 galaxies that have particularly intense [OIII]{lambda}4363 with respect to [OIII]{lambda}5007, which is a proxy for high electron temperature. The metallicity of these candidates was computed using a hybrid technique consistent with the direct method, rendering 196 XMPs. A less restrictive noise constraint provides a larger set with 332 candidates. Both lists are provided in electronic format. The selected XMP sample has a mean stellar mass around 10^8^M_{sun}_, with the dust mass ~10^3^M_{sun}_ for typical star-forming regions. In agreement with previous findings, XMPs show a tendency to be tadpole-like or cometary. Their underlying stellar continuum corresponds to a fairly young stellar population (<1Gyr), although young and aged stellar populations coexist at the low-metallicity starbursts. About 10% of the XMPs show large N/O. Based on their location in constrained cosmological numerical simulations, XMPs have a strong tendency to appear in voids and to avoid galaxy clusters. The puzzling 2%-solar low-metallicity threshold exhibited by XMPs remains.2016ApJ...819..110Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/819/110CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)J/A+A/568/L8 : VUDS extreme emission line 0.2<~z<~0.9 gal. (Amorin+, 2014)J/A+A/558/A18 : Extremely metal-poor (XMP) galaxies HI spectra (Filho+, 2013)J/ApJ/765/140 : SDSS star forming galaxies stacked spectra (Andrews+, 2013)J/A+A/546/A122 : SDSS XMP emission-line galaxies (Izotov+, 2012)J/ApJS/199/26 : The 2MASS Redshift Survey (2MRS) (Huchra+, 2012)J/ApJ/743/77 : Paper I. XMP galaxies in SDSS (Morales-Luis+, 2011)J/AJ/142/170 : ALFALFA survey: the {alpha}.40 HI sources (Haynes+, 2011J/MNRAS/398/451 : PopStar I: Evolutionary synthesis models (Molla+, 2009)J/A+A/448/955 : Abundances of emission galaxies in SDSS-DR3 (Izotov+, 2006)J/ApJS/161/240 : High-ionization emission in metal-poor BCDs (Thuan+, 2005)J/ApJS/153/429 : SDSS strong emission line HII galaxies (Kniazev+, 2004)J/ApJS/147/29 : BRHalpha data of blue compact dwarf gal. (Gil De Paz+, 2003)J/A+AS/91/285 : HII galaxies spectrophotometric catalogue (Terlevich+, 1991)http://wwwmpa.mpa-garching.mpg.de/SDSS/DR7/ : MPA-JHU DR7 releasehttp://www.sdss.org/surveys/eboss/ : eBOSS home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/819/110https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/819/110http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/819/110https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/819/110https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/819/110http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/819/110GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/819/110/table1 (Extremely metal poor galaxies selected in this study)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/819/110/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/819/110/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/819/110/table1?GETtext/xml+votable180.050000true4.1558330.6413330.005555555555555556Cone search capability for table J/ApJ/819/110/table2 (Candidate extremely metal-poor galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/819/110/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/819/110/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/819/110/table2?GETtext/xml+votable180.050000true0.03751.2399440.0055555555555555565/4442 6/0 4145 4251 4293 4344 4348 4425 4441 4543 4568 4588 4655 4667 4802 4804 4896-4897 4948 5018 5020 5044 5176 5180 5315 5332 5357-5359 5392 5441 5501 5543 5556 5600 5606 5615 5617-5618 5635 5643 5646-5647 5655 5758 5877 5916 5924 5942 5964 5977 5983 6010-6011 6014 6047 6058 6087 6115 6168 6226 6367 6391 6406 6433 6642 7204 7208 7254 7272 7281 7291 7331 7399 7431 7445 7486 7504 7605 8272 8299 8308 8321 8325 8379 8432 8683 8689 8705 8718 8747 8759 8831 8866 8892 8897 8914 8927 8935 8958 9041 9119 9166 9192 9203 9345 9347 9382 9394 9433 9438 9870 9950 9955 10028 10107 10213 10215 10217 10247 10301 10359 10388 10417 10437 10455 10481 10494 10565 10587 10639 10712 10745 10754 10766 10768 10844 10848 10896 10906 10999 11005 11031 11054 11056 11062 11116 11132 11143 11177 11197 11254 11313 11394 11423 11470 11569 11776 12404 17234 17264 17516 17558 17578 17582 17746 17752-17753 17762 17764 17772 17812 17817 17827 17834 17841 17998 18007 18011 18020-18021 18026 18033 18066 18071 18075 18077 18085-18087 18112 18178 18392 18521 18534 18581 18765 18767 18787 18789 18844 18850 18860 19031 19033 19035-19036 19057 19086 19096 19099 19108 19399 19406 19417 19459 19685 19687 23145 23187 23193 23196 23201 23203-23204 23206 23208 23211 23213 23216 23218 25593 25910 25912 25932 25952 25965 25981 25986 25997 26049 26205 26212 26215 26236 26239 26251 26287 26297 26305 26320 26377 26438 26460 26488 26550 26877 26969 27087 27090 27223 27342 27347 27387 27401 27407 27482 27510 27548 27562-27563 27576 27591 27654 27719 27745 27765 27775 27801 27809 27829 27840 27842 28049 28129 28147 28154 28162 28178 28240 28297 28312 28337 28353 28358 28396 28411 28435 28537 28670 30035 30037 30044 31331 31396 31419 31439 31477 31624 32415 36861 49017https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/819/110?format=asciidefaultJ/ApJ/819/110/table1Extremely metal poor galaxies selected in this studySimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqRunning index number; sorted according to growing RAmeta.idintIDSource identifier (JHHMMSS.s+DDMMSS.s)meta.id;meta.maincharlogO/H[7/7.7] Log Oxygen abundance; 12+log(O/H) (G1)phys.abundfloate_logO/H[0.07/0.5] Uncertainty in logO/Hstat.error;phys.abundfloatlogN/O[-1.7/-0.8]? Log Nitrogen to Oxygen abundance ratio (G1)phys.abundfloatnullablee_logN/O[0.1/0.4]? Uncertainty in logN/Ostat.error;phys.abundfloatnullablelogU[-2.9/-1.5] Log ionization parameter (G2)phys.ionizParamfloate_logU[0/0.5] Uncertainty in logUstat.error;pos.cartesian.xfloatCHb[0/0.8] Extinction coefficient in H betaobs.atmos.extinctionfloate_CHb[0.01/1.3] Uncertainty in CHbstat.errorfloatMatch[0/7]? Galaxy match code (1)meta.codeintnullablelogO/H-DM[7.3/7.7]? Direct method log Oxygen abundance; 12+log(O/H) (2)phys.abundfloatnullablee_logO/H-DM[0.02/0.2]? Uncertainty in logO/H-DMstat.error;phys.abundfloatnullablePapIDisplay the Paper I data (Morales-Luis+, 2011, J/ApJ/743/77) within 7"meta.ref.urlintnullableI12Display Izotov+, 2012, J/A+A/546/A122, data within 2"meta.ref.urlintnullableSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlchar_RAPositions from names (right ascension part)degpos.eq.ra;meta.main_DEPositions from names (declination part)degpos.eq.dec;meta.mainJ/ApJ/819/110/table2Candidate extremely metal-poor galaxiesSimbadNameSimbad column added by the CDSmeta.idcharnullableNEDnameNED column added by the CDSmeta.idcharXMPmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqRunning index number; sorted according to growing RAmeta.idintIDSource identifier (JHHMMSS.s+DDMMSS.s)meta.id;meta.maincharprimarylogO/H[6.9/7.7] Log Oxygen abundance; 12+log(O/H) (G1)phys.abundfloate_logO/H[0.07/0.6] Uncertainty in logO/Hstat.error;phys.abundfloatlogN/O[-1.8/-0.8]? Log Nitrogen to Oxygen abundance ratio (G1)phys.abundfloatnullablee_logN/O[0.1/0.5]? Uncertainty in logN/Ostat.error;phys.abundfloatnullablelogU[-3.1/-1.5] Log ionization parameter (G2)phys.ionizParamfloate_logU[0/0.6] Uncertainty in logUstat.error;pos.cartesian.xfloatCHb[0/0.8] Extinction coefficient in H betaobs.atmos.extinctionfloate_CHb[0.01/1.3] Uncertainty in CHbstat.errorfloatSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlchar_RAPositions from names (right ascension part)degpos.eq.ra;meta.main_DEPositions from names (declination part)degpos.eq.dec;meta.main