Issue |
A&A
Volume 396, Number 3, December IV 2002
|
|
---|---|---|
Page(s) | 773 - 786 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20021455 | |
Published online | 05 December 2002 |
Cluster of galaxies around seven radio-loud QSOs at
II. K-band images
1
Astrophysikalisches Institut Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
2
Instituto de Física de Cantabria, Universidad de Cantabria-CSIC, Avd. de Los Castros S/N, 35005-Santander, Spain e-mail: gserrano@ifca.unican.es
Corresponding author: S. F. Sánchez, ssanchez@aip.de
Received:
25
July
2002
Accepted:
19
September
2002
We have conducted a NIR study of the environments of seven radio-loud
quasars at redshifts . In present paper we describe deep
K band images obtained for the fields of
arcmin
around the quasars with 3σ limiting magnitudes of
. These fields were previously studied using deep B and
R band images (Sánchez & González-Serrano 1999). Using optical
and NIR data together, a significant excess of galaxies has been found
whose optical-NIR colours, luminosity, spatial scale, and number of
galaxies are compatible with clusters at the redshift of the quasar.
We have selected a sample of cluster candidates analyzing the
vs. K diagram. A ~25% of the candidates present red
optical-NIR colours and an ultraviolet excess. This population has
been also found in clusters around quasars at the same redshifts
(Tanaka et al. 2000; Haines et al. 2001). These galaxies seem to
follow a mixed evolution: a main passive evolution plus late star
formation processes. The quasars do not inhabit the core of the
clusters, being found in the outer regions. This result agrees with
the hypothesis that the origin/feeding mechanism of the nuclear
activity is merging processes. The quasars inhabit the region where a
collision is most likely to produce a merger.
Key words: galaxies: clusters: general / quasars: general / radio continuum: galaxies
© ESO, 2002
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