A&A 399, 899-911 (2003)
DOI: 10.1051/0004-6361:20021829
Photometric properties of galaxy population in the cluster EIS 0048-2942 at z ~ 0.64
F. La Barbera1, P. Merluzzi2, A. Iovino3, M. Massarotti2 and G. Busarello21 Università Federico II, Department of Physics, Napoli, Italy
e-mail: labarber@na.astro.it
2 I.N.A.F., Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
e-mail: gianni@na.astro.it
3 I.N.A.F., Istituto Nazionale di Astrofisica Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
(Received 11 November 2002 / Accepted 9 December 2002 )
Abstract
Deep photometric data in the
V-,
R-,
I-,
z- and
K-bands for
the cluster of galaxies EIS 0048-2942 are used to investigate the
properties of the galaxy populations at
in a
field of
. The sample of candidate
cluster members (
N = 171) is selected by the photometric
redshift technique and is complete up to
I=22.5. Galaxies
were classified as spheroids and disks according to the shape of the
light profile in the
I-band, as parametrized by the Sersic index. In
both optical and NIR, spheroids define a sharp colour-magnitude
sequence, whose slope and zero points are consistent with a high
formation redshift (
). The disk population occupies
a different region in the colour-magnitude diagram, having bluer
colours with respect to the red sequence. Interestingly, we find some
level of mixing between the properties of the two classes: some disks
lie on the colour-magnitude sequence or are redder, while some
spheroids turn out to be bluer. The spatial distribution of cluster
galaxies shows a clumpy structure, with a main over-density of radius
~
0.5 Mpc, and at least two other clumps distant
~
1 Mpc from the center. The various sub-structures are
mostly populated by the red galaxies, while the blue population has an
almost uniform distribution. The fraction of blue galaxies in
EIS 0048-2942 is
. This is much lower
than what expected on the basis of the Butcher-Oemler effect at lower
redshifts.
Key words: galaxies: clusters: individual: EIS 0048-2942 -- galaxies: evolution -- galaxies: fundamental parameters -- galaxies: photometry
Offprint request: P. Merluzzi, merluzzi@na.astro.it
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© ESO 2003
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