Issue |
A&A
Volume 409, Number 1, October I 2003
|
|
---|---|---|
Page(s) | 37 - 52 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20031073 | |
Published online | 17 November 2003 |
Homogeneity of early-type galaxies across clusters
INAF – Osservatorio Astronomico di Brera, Milano, Italy
Corresponding author: andrea@brera.mi.astro.it
Received:
13
March
2003
Accepted:
7
July
2003
We studied the homogeneity, across clusters, of the color of the red
sequence (the intercept of the color-magnitude relation) of 158 clusters and groups
detected in the Early Data Release of the Sloan Digital Sky Survey (EDR–SDSS) in the
redshift range . We found a high degree of homogeneity: the color of the
red sequence shows an intrinsic scatter of 0.02 mag across clusters, suggesting that
either galaxies on the red sequence formed a long time ago (
) or else their
star formation is universally delayed with preservation of a small spread in age
formation. The latter possibility is ruled out by the mere existence of galaxies at
high redshift. While the old age of ellipticals was already been claimed for a small
heterogeneous collection of clusters, most of which are rich ones, we found that it
holds for ten to one hundred large sample, representative of all clusters and groups
detected on the EDR–SDSS. Hence we suggest the possible universality of the color of
the galaxies on the red sequence. Furthermore, the sample includes a large number of
very poor clusters (also called groups), not studied in previous works, for which the
hierarchical and monolithic scenarios of elliptical formation predict different colors
for the brightest ellipticals. The observed red sequence color does not depend on
cluster/group richness at a level of 0.02 mag, while a ~0.23 mag effect is expected
according to the hierarchical prediction. Therefore, the stellar population of red
sequence galaxies is similar in clusters and groups, in spite of different halo
histories. Finally, since the observed rest-frame color of the red sequence does not
depend on environment and redshift, it can be used as a distance indicator, with an
error
, a few time better than the precision achieved by other
photometric redshift estimates and twice better
than the precision of the Fundamental
Plane for a single galaxy at the median redshift of the EDR–SDSS.
Key words: galaxies: evolution / galaxies: clusters: general
© ESO, 2003
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