NGC 6558 : a blue horizontal branch moderately metal-poor globular cluster in the bulge
dc.contributor.author | Barbuy, Beatriz | pt_BR |
dc.contributor.author | Zoccali, Manuela | pt_BR |
dc.contributor.author | Ortolani, Sergio | pt_BR |
dc.contributor.author | Minniti, Dante | pt_BR |
dc.contributor.author | Hill, Vanessa | pt_BR |
dc.contributor.author | Renzini, Alvio | pt_BR |
dc.contributor.author | Bica, Eduardo Luiz Damiani | pt_BR |
dc.contributor.author | Gómez, Ana | pt_BR |
dc.date.accessioned | 2014-12-13T02:18:07Z | pt_BR |
dc.date.issued | 2007 | pt_BR |
dc.identifier.issn | 0004-6256 | pt_BR |
dc.identifier.uri | http://hdl.handle.net/10183/108242 | pt_BR |
dc.description.abstract | We present, for the first time, a detailed abundance analysis of five giant stars in the moderately metal-poor bulge globular cluster NGC 6558. Spectra have been obtained at the VLT with the multifiber spectrograph FLAMES in GIRAFFE mode (R~22,000). The resulting iron abundance is [Fe/H]= −0.97±0.15, in good agreement with the metallicity inferred from the slope of the red giant branch, but unusually high for a cluster with such a blue horizontal branch, possibly indicating an old age. A color-magnitude diagram in Vand I, based on photometry obtained with the Wide-Field Imager at ESO, is also presented. An isochrone of 14 Gyr fits the evolutionary sequences, confirming an old age. NGC 6558 is another ‘‘second-parameter’’ bulge cluster. The metallicity derived is near the end of the low-metallicity tail of the bulge field-star distribution; hence, it presumably formed at the very early stages of the bulge formation. Abundance ratios showenhancements of the -elements oxygen, magnesium, and silicon,with [O/Fe] = +0.38, [Mg/Fe] = +0.24, [Si/Fe] = +0.23, and solar calcium and titanium. The r-element europium is also enhanced by [Eu/Fe] = +0.36. The odd-Z elements sodium and aluminum, as well as the s-elements barium and lanthanum, show solar ratios. A heliocentric radial velocity of vr hel = −197.3 ±4 km s-ˡ is found for NGC 6558. | en |
dc.format.mimetype | application/pdf | pt_BR |
dc.language.iso | eng | pt_BR |
dc.relation.ispartof | The astronomical journal. Vol. 134, no. 4 (Oct. 2007), p. 1613-1625 | pt_BR |
dc.rights | Open Access | en |
dc.subject | Globular clusters: general | en |
dc.subject | Aglomerados estelares globulares | pt_BR |
dc.subject | Evolucao estelar | pt_BR |
dc.subject | Globular clusters: individual (NGC 6558) | en |
dc.subject | Espectros estelares | pt_BR |
dc.subject | Estrelas gigantes | pt_BR |
dc.title | NGC 6558 : a blue horizontal branch moderately metal-poor globular cluster in the bulge | pt_BR |
dc.type | Artigo de periódico | pt_BR |
dc.identifier.nrb | 000625421 | pt_BR |
dc.type.origin | Estrangeiro | pt_BR |
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