Bibcode
Barrena, Rafael
Bibliographical reference
PhD Thesis, Instituto de Astrofisica de Canarias, Tenerife, Spain, 2004.
Advertised on:
11
2004
Citations
1
Refereed citations
1
Description
This thesis is divided into two very related parts. In the first part we
implement and apply a galaxy cluster detection method, based on
multiband observations in visible. For this purpose, we use a new
algorithm, the Voronoi Galaxy Cluster Finder, which identifies
overdensities over a Poissonian field of objects. By applying this
algorithm over four photometric bands (B, V, R and I) we reduce the
possibility of detecting galaxy projection effects and spurious
detections instead of real galaxy clusters.
The B, V, R and I photometry allows a good characterization of galaxy
systems. Therefore, we analyze the colour and early-type sequences in
the colour-magnitude diagrams of the detected clusters. This analysis
helps us to confirm the selected candidates as actual galaxy systems. In
addition, by comparing observational early-type sequences with a
semiempirical model we can estimate a photometric redshift for the
detected clusters.
We will apply this detection method on four 0.5x0.5 square degrees
areas, that partially overlap the Postman Distant Cluster Survey (PDCS).
The observations were performed as part of the International Time
Programme 1999-B using the Wide Field Camera mounted at Isaac Newton
Telescope (Roque de los Muchachos Observatory, La Palma island, Spain).
The B and R data obtained were completed with V and I photometry
performed by Marc Postman.
The comparison of our cluster catalogue with that of PDCS reveals that
our work is a clear improvement in the cluster detection techniques. Our
method efficiently selects galaxy clusters, in particular low mass
galaxy systems, even at relative high redshift, and estimate a precise
photometric redshift.
The validation of our method comes by observing spectroscopically
several selected candidates. By comparing photometric and spectroscopic
redshifts we conclude: 1) our photometric estimation method gives an
precision lower than 0.1; 2) our detection technique is even able to
detect galaxy systems at z~0.7 using visible photometric bands.
In the second part of this thesis we analyze in detail the dynamical
state of 1E0657-56 (z=0.296), a hot galaxy cluster with strong X-ray and
radio emissions. Using spectroscopic and photometric observations in
visible (obtained with the New Technology Telescope and the Very Large
Telescope, both located at La Silla Observatory, Chile) we analyze the
velocity field, morphology, colour and star formation in the galaxy
population of this cluster.
1E0657-56 is involved in a collision event. We identify the substructure
involved in this collision and we propose a dynamical model that allows
us to investigate the origins of X-ray and radio emissions and the
relation between them.
The analysis of 1E0657-56 presented in this thesis constitutes a good
example of what kind of properties could be studied in some of the
clusters catalogued in first part of this thesis. In addition, the
detailed analysis of this cluster represents an improvement in the study
of the origin of X-ray and radio emissions and merging processes in
galaxy clusters.