期刊
ASTRONOMY & ASTROPHYSICS
卷 489, 期 3, 页码 1065-U48出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361:200810084
关键词
galaxies : individual : NGC 45; galaxies : star clusters
资金
- European Southern Observatory (ESO) [ID 077.D0403(A), 077.D-0403(B)]
Context. Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. Aims. Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (19), as well as several young star clusters. In this work we aim to confirm the bona fide globular cluster status for 8 of 19 globular cluster candidates and to derive metallicities, ages, and velocities. Methods. VLT/FORS2 multislit spectroscopy in combination with the Lick/IDS system was used to derive velocities and to constrain metallicities and [alpha/Fe] element ratio of the globular clusters. Results. We confirm the 8 globular clusters as bona fide globular clusters. Their velocities indicate halo or bulge-like kinematics, with little or no overall rotation. From absorption indices such as H beta, H gamma, and H delta and the combined [MgFe]' index, we found that the globular clusters are metal-poor [Z/H] <=-0.33 dex and [alpha/Fe] <= 0.0 element ratio. These results argue in favor of a population of globular clusters formed during the assembling of the galaxy.
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