J/A+A/426/399ivo://CDS.VizieR/J/A+A/426/399doi:10.26093/cds/vizier.34260399CDSJamet L.Perez E.Cervino M.Stasinska G.Gonzalez-Delgado R.M.,Vilchez J.M.2016-09-27T07:51:16Z2016-09-27T08:50:31ZCDS support team

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

cds-question@unistra.frh-ii-regionshst-photometryWe present the results of a double analysis of the ionizing cluster in NGC 588, a giant HII region (GHR) in the outskirts of the nearby galaxy M33. For this purpose, we obtained ground based long-slit spectroscopy and combined it with archival ground based and space borne imaging and spectroscopy, in the wavelength range 1100-9800{AA}. A first modeling of the cluster was performed using integrated properties, such as the spectral energy distribution (SED), broad band colors, nebular emission H{beta} equivalent width, the main ultraviolet resonance lines, and the presence of Wolf-Rayet star features. By applying standard assumptions about the initial mass function (IMF), we were unable to fit satisfactorily these observational data. This contradictory result led us to carry out a second modeling, based on a resolved photometric analysis of individual stars in Hubble Space Telescope (HST) images, by means of finding the best fit isochrone in color-magnitude diagrams (CMD), and assigning a theoretical SED to each individual star. The overall SED of the cluster, obtained by integrating the individual stellar SEDs, is found to fit better the observed SED than the best solution found through the integrated first analysis, but at a significantly later stage of evolution of the cluster of 4.2Myr, as obtained from the best fit to the CMD. A comparative analysis of both methods traces the different results to the effects of statistical fluctuations in the upper end of the IMF, which are significant in NGC 588, with a computed cluster mass of 5600M_{sun}_, as predicted by Cervino et al. (2002A&A...381...51C). We discuss the results in terms of the strong influence of the few most massive stars, six in the case of NGC 588, that dominate the overall SED and, in particular, the ionizing far ultraviolet range beyond the Lyman limit.2004A&A...426..399Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/426/399CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/426/399https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/426/399http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/426/399https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/426/399https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/426/399http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/426/399GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/426/399/table4 (Positions, reddened absolute magnitudes, E(B-V) coefficients, and initial masses of the brightest stars of NGC 588)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/426/399/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/426/399/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/426/399/table4?GETtext/xml+votable180.050000true23.188458330.64955560.0055555555555555566/2154https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/426/399?format=asciidefaultJ/A+A/426/399/table4Positions, reddened absolute magnitudes, E(B-V) coefficients, and initial masses of the brightest stars of NGC 588E(B-V)Redenningmagphot.color.excessfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqSequential numbermeta.recordintRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainF547MHST/WFPC2 F547M absolute magnitudemagphys.magAbsfloate_F547Mrms uncertainty on F547Mmagstat.errorfloatF439WHST/WFPC2 F439W absolute magnitudemagphys.magAbsfloate_F439Wrms uncertainty on F439Wmagstat.errorfloatF336WHST/WFPC2 F336W absolute magnitudemagphys.magAbsfloate_F336Wrms uncertainty on F336Wmagstat.errorfloatF170WHST/WFPC2 F170W absolute magnitudemagphys.magAbsfloate_F170Wrms uncertainty on F170Wmagstat.errorfloatF469N? HST/WFPC2 F469N absolute magnitudemagphys.magAbsfloatnullablee_F469N? rms uncertainty on F469Nmagstat.errorfloatnullablee_E(B-V)rms uncertainty on E(B-V)magstat.errorfloatn_E(B-V)[a] a for E(B-V) values eventually set to 0.11meta.notecharMiniInitial masssolMassphys.massfloat