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Issue A&A
Volume 489, Number 3, October III 2008
Page(s) 1065 - 1071
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:200810084
Published online 08 August 2008



A&A 489, 1065-1071 (2008)
DOI: 10.1051/0004-6361:200810084

Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

M. D. Mora1, 2, S. S. Larsen3, and M. Kissler-Patig2

1  Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso. Av. Gran Bretaña 1111, Valparaíso, Chile
    e-mail: mmora@dfa.uv.cl
2  European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
    e-mail: mkissler@eso.org
3  Astronomical Institute, University of Utrecht, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
    e-mail: S.S.Larsen@uu.nl

Received 28 April 2008 / Accepted 24 July 2008

Abstract
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] $\leq-0.33$ dex and [ $\alpha$/Fe] $\leq$ 0.0 element ratio. These results argue in favor of a population of globular clusters formed during the assembling of the galaxy.


Key words: galaxies: individual: NGC 45 -- galaxies: star clusters



© ESO 2008

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