Journal Article

Young globular clusters in an old S0: clues to the formation history of NGC 4570*

R. Kotulla, U. Fritze and P. Anders

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 3, pages 1149-1156
Published in print July 2008 | ISSN: 0035-8711
Published online May 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13297.x
Young globular clusters in an old S0: clues to the formation history of NGC 4570*

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We here present our first attempt to use globular clusters as tracers of their parent galaxy's formation history. Globular cluster systems of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak globular clusters are generally believed to be old and metal-poor. The ages, metallicities, and the origin of the red-peak globular clusters are being debated. We here present our analysis of the ages and metallicities of the red peak globular clusters in the Virgo S0 NGC 4570 using deep Ks-band photometry from NTT/SOFI (ESO programme ID 079.B-0511) for the red-peak globular clusters in combination with HST-ACS archival data to break the age–metallicity degeneracy.

We analyze the combined g, z and Ks spectral energy distribution by comparison with a large grid of GALEV evolutionary synthesis models for star clusters with different ages and metallicities. This analysis reveals a substantial population of intermediate-age (1–3 Gyr) and metal-rich (≈ solar metallicity) globular clusters. We discuss their age and metallicity distributions together with information on the parent galaxy from the literature to gain insight into the formation history of this galaxy.

Our results prove the power of this approach to reveal the (violent) star formation and chemical enrichment histories of galaxies on the basis of combined optical and near-infrared photometry.

Keywords: galaxies: elliptical and lenticular, cD; galaxies: formation; galaxies: individual: NGC 4570; galaxies: star clusters

Journal Article.  5845 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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