EDP Sciences
Free Access
Volume 429, Number 1, January I 2005
Page(s) 101 - 114
Section Cosmology (including clusters of galaxies)
DOI https://doi.org/10.1051/0004-6361:20041215
Published online 13 December 2004

A&A 429, 101-114 (2005)
DOI: 10.1051/0004-6361:20041215

The intermediate-redshift galaxy cluster CL 0048-2942

Stellar populations
M. Serote Roos1, C. Lobo2, 3, F. Durret4, A. Iovino5 and I. Márquez6

1  Centro de Astronomia e Astrofísica da Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
    e-mail: serote@oal.ul.pt
2  Depto. de Matemática Aplicada, Faculdade de Ciências, Univ. do Porto, R. do Campo Alegre 687, 4169-007 Porto, Portugal
3  Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
    e-mail: lobo@astro.up.pt
4  Institut d'Astrophysique de Paris, 98bis Bd. Arago, 75014 Paris, France
    e-mail: durret@iap.fr
5  Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
    e-mail: iovino@brera.mi.astro.it
6  Instituto de Astrofísica de Andalucía (CSIC), Camino Bajo de Huétor, 24, 18008 Granada, Spain
    e-mail: isabel@iaa.es

(Received 3 May 2004 / Accepted 28 August 2004 )

We present a detailed study of the cluster CL 0048-2942, located at $z \sim 0.64$, based on a photometric and spectroscopic catalogue of 54 galaxies in a $5 \times 5$ arcmin 2 region centred in that cluster. Of these, 23 galaxies were found to belong to the cluster. Based on this sample, the line-of-sight velocity dispersion of the cluster is approximately $680 \pm 140$ km s -1. We have performed stellar population synthesis in the cluster members as well as in the field galaxies of the sample and found that there are population gradients in the cluster with central galaxies hosting mainly intermediate/old populations whereas galaxies in the cluster outskirts show clearly an increase of younger populations, meaning that star formation is predominantly taking place in the outer regions of the cluster. In a general way, field galaxies seem to host less evolved stellar populations than cluster members. In fact, in terms of ages, young supergiant stars dominate the spectra of field galaxies whereas cluster galaxies display a dominant number of old and intermediate age stars. Following the work of other authors (e.g. Dressler et al. 1999) we have estimated the percentage of K+A galaxies in our sample and found around 13% in the cluster and 10% in the field. These values were estimated through means of a new method, based on stellar population synthesis results, that takes into account all possible absorption features in the spectrum and thus makes optimal use of the data.

Key words: galaxies: clusters: individual: CL 0048-2942 -- galaxies: clusters: general -- galaxies: distances and redshifts -- galaxies: stellar content

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© ESO 2004

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