J/A+A/686/A185ivo://CDS.VizieR/J/A+A/686/A185doi:10.26093/cds/vizier.36860185CDSUpadhyaya A.Marques-Chaves R.Schaerer D.Martins F.Perez-Fournon I.,Palacios A.Stanway E.R.2024-11-07T20:03:55Z2024-06-12T09:24:08ZCDS support team

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

cds-question@unistra.frgalaxiesultraviolet-astronomyspectroscopyWe present a comprehensive analysis of the presence of very massive stars (VMS>100M_{sun}_) in the integrated spectra of 13 UVbright star-forming galaxies at 2.2<~z<~3.6 taken with the Gran Telescopio Canarias (GTC). These galaxies have very high UV absolute magnitudes (M_UV_~-24), intense star formation (star formation rate ~100-1000M_{sun}/yr), and metallicities in the range of 12+log(O/H)~8.10-8.50 inferred from strong rest-optical lines. The GTC rest-UV spectra reveal spectral features indicative of very young stellar populations with VMS, such as strong P-Cygni line profiles in the wind lines NV {lambda}1240 and CIV {lambda}1550 along with intense and broad He ii 1640 emission with equivalent width (EW_0_)~1.40-4.60{AA}, and full width half maximum (FWHM)~1150-3170km/s. A Comparison with known VMS-dominated sources and typical galaxies without VMS reveals that some UV-bright galaxies closely resemble VMS-dominated clusters (e.g., R136 cluster). The presence of VMS is further supported by a quantitative comparison of the observed strength of the He ii emission with population synthesis models with and without VMS, where models with VMS are clearly preferred. Employing an empirical threshold for EW_0_ (HeII)>=3.0{AA}, along with the detection of other VMS-related spectral profiles (NIV {lambda}1486; {lambda}1719), we classify nine out of 13 UV-bright galaxies as VMS-dominated sources. This high incidence of VMS-dominated sources in the UV-bright galaxy population (~70%) contrasts significantly with the negligible presence of VMS in typical L*_UV_ LBGs at similar redshifts (<1%). Our results thus indicate that VMS are common in UV-bright galaxies, suggesting a different initial mass function (IMF) with upper mass limits between 175M_{sun}_ and 475M_{sun}_.2024A&A...686A.185Uhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/686/A185CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/686/A185https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/686/A185http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/686/A185https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/686/A185https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/686/A185http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/686/A185GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/686/A185/table1 (Summary of the GTC observations)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/686/A185/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/686/A185/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/686/A185/table1?GETtext/xml+votable180.050000true1.68637524.88144170.0055555555555555566/2601 4333 5758 10286 10670 17642 17802 18006 19794 19962 20249 27650 277262.762881831355591e-19 3.3785437584409506e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/686/A185?format=asciiUVdefaultJ/A+A/686/A185/table1Summary of the GTC observationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName (JHHMM+DDMM)meta.id;meta.maincharn_Name[abc] Note on Name (1)meta.notecharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainzRedshiftsrc.redshiftfloatRmagR-band magnitude (AB)magphot.mag;em.opt.RfloatDateOOptical spectroscopy observation datetime.epochnullableExpTimeOOptical spectroscopy exposure timestime.duration;obs.exposureintDateNNear-IR spectroscopy observation datetime.epochnullableExpTimeN? Near-IR spectroscopy exposure timestime.duration;obs.exposureintnullablespShow the spectrummeta.ref.urlcharFileNameName of the spectrum file in subdirectory spmeta.id;meta.filecharJ/A+A/686/A185/stackStack spectrum of UV-bright galaxiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaRest-frame wavelength0.1nmem.wlintFluxFlux in F_lambda_ unitphot.fluxdoublee_Flux1 sigma uncertainty associated with the flux in F_lambda_ unitstat.error;phot.fluxdouble