Globular cluster content and evolutionary history of NGC 147

被引：0

作者：

Sharina, M. ^{[1
,2
]}

Davoust, E. ^{[2
]}

机构：

[1] Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR 369167, Russia

[2] Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue E. Belin, 31400 Toulouse, France

来源：

Astronomy and Astrophysics | 2009年 / 497卷 / 01期

关键词：

Context. Globular clusters are representative of the oldest stellar populations. It is thus essential to have a complete census of these systems in dwarf galaxies; from which more massive galaxies are progressively formed in the hierarchical scenario. Aims. We present the results of spectroscopic observations of eight globular cluster candidates in NGC 147; a satellite dwarf elliptical galaxy of M 31. Our goal is to make a complete inventory of the globular cluster system of this galaxy; determine the properties of their stellar populations; and compare these properties with those of systems of globular clusters in other dwarf galaxies. Methods. The candidates were identified on Canada-France-Hawaii telescope photographic plates. Medium resolution spectra were obtained with the SCORPIO spectrograph at the prime focus of the 6 m telescope of the Russian Academy of Sciences. They were analyzed using predictions of stellar population synthesis models. Results. We were able to confirm the nature of all eight candidates; three of which (GC5; GC7. and GC10) are indeed globular clusters; and to estimate evolutionary parameters for the two brightest ones and for Hodge II. The bright clusters GC5 and GC7 appear to have metallicities([Z/H] ∼-1.5 ÷-1.8) that are lower than the oldest stars in the galaxy. The fainter GC Hodge II has a metallicity [Z/H] = -1.1; similar to that of the oldest stars in the galaxy. The clusters GC5 and GC7 have low alpha-element abundance ratios. The mean age of the globular clusters in NGC 147 is 9 ± 1 Gyr. We also measured the radial velocities of Hodge II and IV; and derived a mass of NGC 147 in good agreement with the value from the literature. The frequency; Sn; 6.4; and mass fraction; T = 14 of globular clusters in NGC 147 appear to be higher than those for NGC 185 and 205. Conclusions. Our results indicate that the bright clusters GC5; GC7. and Hodge III formed in the main star-forming period ∼8-10 Gyr ago; while the fainter clusters Hodge I and D formed together with the second generation of field stars. © ESO 2009;

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页码：65 / 80