J/A+A/643/A80ivo://CDS.VizieR/J/A+A/643/A80doi:10.26093/cds/vizier.36430080CDSPerez-Montero E.Kehrig C.Vilchez J.M.Garcia-Benito R.,Duarte Puertas S.Iglesias-Paramo J.2021-09-09T08:28:03Z2020-11-06T08:32:08ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopychemical-abundancesStar-forming galaxies with nebular HeII emission contain very energetic ionizing sources of radiation, which can be considered as analogs to the major contributors of the reionization of the Universe in early epochs. It is therefore of great importance to provide a reliable absolute scale for the equivalent effective temperature (T*) for these sources. We study a sample of local (z<0.2) star-forming galaxies showing optical nebular HeII emission using the so-called softness diagrams, involving emission lines of two elements in two consecutive stages of ionization (e.g., [SII]/[SIII] vs. [OII]/[OIII]). We use for the first time the HeI/HeII ratio in these diagrams in order to explore the higher range of T* expected in these objects, and to investigate the role of possible mechanisms driving the distribution of galaxy points in these diagrams. We build grids of photoionization models covering different black-body temperatures, model cluster atmospheres, and density-bounded geometries to explain the conditions observed in the sample. We verified that the use of the softness diagrams including the emission-line ratio HeI/HeII combined with black-body photoionization models can provide an absolute scale of T* for these objects. The application of a Bayesian-like code indicates T* in the range 50-80kK for the sample of galaxies, with a mean value higher than 60kK. The average of these high temperature values can only be reproduced using cluster model populations with nearly metal-free stars, although such ionizing sources cannot explain either the highest T* values, beyond 1{sigma}, or the dispersion observed in the softness diagrams. According to our photoionization models, most sample galaxies could be affected to some extent by ionizing photon leaking, presenting a mean photon absorption fraction of 26% or higher depending on the metallicity assumed for the ionizing cluster. The entire range of HeI/HeII, [SII]/[SIII], and [OII]/[OIII] ratios for these HeII-emitting galaxies is reproduced with our models, combining nearly metal-free ionizing clusters and photon leaking under different density-bounded conditions.2020A&A...643A..80Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/643/A80CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/421/1043 : Emission-line galaxies from SDSS DR7 (Shirazi+, 2012)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/643/A80https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/643/A80http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/643/A80https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/643/A80https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/643/A80http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/643/A80GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/643/A80/table (Measured reddening corrected relative to H{beta} emission line and derived properties for the HeII-emitters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/643/A80/table?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/643/A80/table?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/643/A80/table?GETtext/xml+votable180.050000true146.0078011-0.64227390.0055555555555555566/1700 4109 4149 4181 4298 4381 4417 4470 4630 4685 4758 4891 5026 5128 5190 5203 5223 5290 5342 5346 5359 5440 5501 5531 5556 5592 5617 5624 5669 5933 5940 5967 6005 6075 6396 6470 6609 7185 7207 7243 7252 7303 7371 7381 7416 8328 8359 8509 8678 8729 8862 8897 9018 9039 9098 9109 9111 9182 9187 9190 9317 9481 9855 9870 9880 10016 10104 10348 10431 10433 10441 10472 10524 10527 10540 10640 10666 10755 10782 10818 10888 10905 10911 10965 10970 11009 11033 11090 11218 11239 11355 11433-11434 11782 11907 11909 11928 11941 17303 17502 17754 17858 18002 18019 18027 18084 18098 18235 18388 18844 19028 19417 19678 19754 19756 20002 21877 25594 25851 25938 25959 26178 26205 26303 26344 26390 26443 26464 26580 26617 27049 27053 27056 27199 27409 27431 27446 27494 27555 27575 27581 27604 27641 27653 27657 27723 27765 27811 27855 27884 27948 28055 28077 28147 28180 28221 28240 28255 28269 28272 28290 28335 28421 28460 28470 28476 28598 28613 28617 30035 31316 31487 31679 31714 32440 32682 36766 36785https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/643/A80?format=asciidefaultJ/A+A/643/A80/tableMeasured reddening corrected relative to H{beta} emission line and derived properties for the HeII-emittersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintS12Display the Shirazi et al. (2012, Cat. J/MNRAS/421/1043) datameta.ref.urlcharPlateSDSS platemeta.noteintMJDSDSS mjdmeta.idintFiberSDSS fiberidmeta.noteintzRedshiftsrc.redshiftfloatWRclass[0/1] WR class (1)meta.codeintI([OII]3727)I([OII] 3727)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I([OII]3727)Error for I([OII] 3727)/I(Hbeta)stat.errorfloatI([OIII]4363)I([OIII] 4363)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I([OIII]4363)Error for I([OIII] 4363)/I(Hbeta)stat.errorfloatI(HeII3727)I(HeII 3727)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I(HeII3727)Error for I(HeII 3727)/I(Hbeta)stat.errorfloatI([OIII]5007)I([OIII] 5007)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I([OIII]5007)Error for I([OIII] 5007)/I(Hbeta)stat.errorfloatI(HeI5876)I(HeI 5876)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I(HeI5876)Error for I(HeI 5876)/I(Hbeta)stat.errorfloatI([NII]6583)I([NII] 6583)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I([NII]6583)Error for I([NII] 6583)/I(Hbeta)stat.errorfloatI([SII]6717+6731)I([SII] 6717+6731)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I([SII]6717+6731)Error for I([SII] 6717+6731)/I(Hbeta)stat.errorfloatI([SIII]9069)I([SIII] 9069)/I(Hbeta) reddening correctedspect.line.intensity;arith.ratiofloate_I([SIII]9069)Error for I([SIII] 9069)/I(Hbeta)stat.errorfloat12+log(O/H)12+log(O/H) as derived from HCmphys.abundfloate_12+log(O/H)Error for 12+log(O/H)stat.errorfloatTeffEffective temperature in KKphys.temperatureinte_TeffError for effective temperature in KKstat.error;phys.temperature.effectiveintlogUbblog of the ionization parameter as derived from black-body gridsphys.ionizParamfloate_logUbbError for the ionization parameter as derived from bb modelsstat.errorfloatfabsAbsorption fraction of ionizing photons as derived from BPASS v.2.1 (2)phys.absorption;arith.ratiofloate_fabsError for fabsstat.errorfloatlogUBPASSlog of the ionization parameter as derived from BPASS modelsphys.ionizParamfloate_logUBPASSError for log U as derived from BPASS modelsstat.errorfloatSloanDisplay the SDSS data for this quasarmeta.ref.urlcharSimbadNameSimbad column added by the CDSmeta.idchar_RAPositions from SDSS (right ascension part)degpos.eq.ra;meta.main_DEPositions from SDSS (declination part)degpos.eq.dec;meta.main