66 research outputs found
XMM-Newton temperature maps for five intermediate redshift clusters of galaxies
We have analyzed XMM-Newton archive data for five clusters of galaxies
(redshifts 0.223 to 0.313) covering a wide range of dynamical states, from
relaxed objects to clusters undergoing several mergers. We present here
temperature maps of the X-ray gas together with a preliminary interpretation of
the formation history of these clusters.Comment: 4 pages, 2 figs. Accepted for publication in the Proceedings of the
36th COSPAR Scientific Assembl
A catalogue of velocities in the direction of the cluster of galaxies Abell 496
We present a catalogue of velocities for 466 galaxies in the direction of the
cluster Abell 496, in a region covering about 160' x 160' (9.2 x 9.2 Mpc for an
average redshift for Abell 496 of 0.0331, assuming H=50 km s
Mpc). This catalogue includes previously published redshifts by Proust
et al. (1987), Quintana and Ramirez (1990) and Malumuth et al. (1992),
redshifts from the CfA redshift survey, together with our new measurements. A
total of 274 galaxies have velocities in the 7800-11800 km/s interval, and will
be considered as members of the cluster. Abell 496 therefore becomes one of the
few clusters with a high number of measured redshifts; its physical properties
are investigated in a companion paper.Comment: Accepted for publication in Astronomy & Astrophysics, Supplement
Serie
A multi-wavelength analysis of the cluster of galaxies ABCG 194
(Abridged) We present a morphological and structural analysis of the Richness
zero cluster ABCG 194, known as a ``linear cluster'', based on a catalogue of
97 galaxies with B magnitudes and redshifts, a ROSAT PSPC image and radio data.
The overall large scale structure is rather smooth and comparable at optical
and X-ray wavelengths. The cluster is elongated along PA ; however
it appears as ``linear'' when taking into account only galaxies in the very
central part (the axial ratio varies from 0.2 in the central region to 0.8 for
a larger region). We have obtained the galaxy and X-ray emitting gas density
profiles and estimated the X-ray gas and dynamical masses.
At smaller scales, the analysis of both positions and velocities reveals the
existence of several groups; a main structure with a nearly gaussian velocity
distribution is exhibited. The velocity dispersion is small ( =
360 \kms). A wavelet analysis of the X-ray image reveals no large scale
substructures. Small scale X-ray sources are detected, mainly corresponding to
individual galaxies.
ABCG 194 is overall a poor and cold relaxed cluster. We compare how its
characteristics fit into various correlations found in the literature, but
generally for richer/hotter clusters.Comment: Accepted for publication in Astronomy & Astrophysic
The 3XMM/SDSS Stripe 82 Galaxy Cluster Survey: Cluster catalogue and discovery of two merging cluster candidates
We present a galaxy cluster survey based on XMM-Newton observations that are
located in Stripe 82 of the Sloan Digital Sky Survey (SDSS). The survey covers
an area of 11.25 deg. The X-ray cluster candidates were selected as
serendipitously extended detected sources from the third XMM-Newton
serendipitous source catalogue (3XMM-DR5). A cross-correlation of the candidate
list that comprises 94 objects with recently published X-ray and optically
selected cluster catalogues provided optical confirmations and redshift
estimates for about half of the candidate sample. We present a catalogue of
X-ray cluster candidates previously known in X-ray and/or optical bands from
the matched catalogues or NED. The catalogue consists of 54 systems with
redshift measurements in the range of 0.05-1.19 with a median of 0.36. Of
these, 45 clusters have spectroscopic confirmations as stated in the matched
catalogues. We spectroscopically confirmed another 6 clusters from the
available spectroscopic redshifts in the SDSS-DR12. The cluster catalogue
includes 17 newly X-ray discovered clusters, while the remainder were detected
in previous XMM-Newton and/or ROSAT cluster surveys. Based on the available
redshifts and fluxes given in the 3XMM-DR5 catalogue, we estimated the X-ray
luminosities and masses for the cluster sample. We also present the list of the
remaining X-ray cluster candidates (40 objects) that have no redshift
information yet in the literature. Of these candidates, 25 sources are
considered as distant cluster candidates beyond a redshift of 0.6. We also
searched for galaxy cluster mergers in our cluster sample and found two strong
candidates for newly discovered cluster mergers at redshifts of 0.11 and 0.26.
The X-ray and optical properties of these systems are presented.Comment: 17 pages, 12 figures, accepted for publication in A&A, revised
version after language editin
Giant Ringlike Radio Structures Around Galaxy Cluster Abell 3376
In the current paradigm of cold dark matter cosmology, large-scale structures
are assembling through hierarchical clustering of matter. In this process, an
important role is played by megaparsec (Mpc)-scale cosmic shock waves, arising
in gravity-driven supersonic flows of intergalactic matter onto dark
matter-dominated collapsing structures such as pancakes, filaments, and
clusters of galaxies. Here, we report Very Large Array telescope observations
of giant (~2 Mpc by 1.6 Mpc), ring-shaped nonthermal radio-emitting structures,
found at the outskirts of the rich cluster of galaxies Abell 3376. These
structures may trace the elusive shock waves of cosmological large-scale matter
flows, which are energetic enough to power them. These radio sources may also
be the acceleration sites where magnetic shocks are possibly boosting
cosmic-ray particles with energies of up to 10^18 to 10^19 electron volts.Comment: Published on Science, 3 November 2006. Main paper and Supporting
Online Materia
Galaxy Evolution in the Cluster Abell 85: New Insights from the Dwarf Population
We present the first results of a new spectroscopic survey of the cluster
Abell 85 targeting 1466 candidate cluster members within the central 1
deg of the cluster and having magnitudes using VIMOS/VLT and
HYDRA/WIYN. A total of 520 galaxies are confirmed as either relaxed cluster
members or part of an infalling population. A significant fraction are low
mass; the median stellar mass of the sample is , and 25%
have stellar masses below (i.e. 133 dwarf galaxies). We also
identify seven active galactic nuclei (AGN), four of which reside in dwarf host
galaxies. We probe the evolution of star formation rates, based on H
emission and continuum modeling, as a function of both mass and environment. We
find that more star forming galaxies are observed at larger clustercentric
distances, while infalling galaxies show evidence for recently enhanced star
forming activity. Main sequence galaxies, defined by their continuum star
formation rates, show different evolutionary behavior based on their mass. At
the low mass end, the galaxies have had their star formation recently quenched,
while more massive galaxies show no significant change. The timescales probed
here favor fast quenching mechanisms, such as ram-pressure stripping. Galaxies
within the green valley, defined similarly, do not show evidence of quenching.
Instead, the low mass galaxies maintain their levels of star forming activity,
while the more massive galaxies have experienced a recent burst.Comment: 15 pages, 10 figures, accepted for publication in MNRA
The galaxy luminosity function in the cluster of galaxies Abell 496
We have derived the galaxy luminosity function (GLF) in the cluster of
galaxies Abell 496 from a wide field image in the I band. A single Schechter
function reproduces quite well the GLF in the 17 <= I_{AB} <= 22 (-19.5 <= M_I
<= -14.5) magnitude interval, and the power law index of this function is found
to be somewhat steeper in the outer regions than in the inner regions. This
result agrees with the idea that faint galaxies are more abundant in the outer
regions of clusters, while in the denser inner regions they have partly been
accreted by larger galaxies or have been dimmed or even disrupted by tidal
interactions.Comment: Accepted for publication in Astronomy & Astrophysics, final versio
The 3XMM/SDSS Stripe 82 Galaxy Cluster Survey II. X-ray and optical properties of the cluster sample
We present X-ray and optical properties of the optically confirmed galaxy
cluster sample from the 3XMM/SDSS Stripe 82 cluster survey. The sample includes
54 galaxy clusters in the redshift range of 0.05-1.2, with a median redshift of
0.36. We first present the X-ray temperature and luminosity measurements that
are used to investigate the X-ray luminosity-temperature relation. The slope
and intercept of the relation are consistent with those published in the
literature. Then, we investigate the optical properties of the cluster galaxies
including their morphological analysis and the galaxy luminosity functions. The
morphological content of cluster galaxies is investigated as a function of
cluster mass and distance from the cluster center. No strong variation of the
fraction of early and late type galaxies with cluster mass is observed. The
fraction of early type galaxies as a function of cluster radius varies as
expected. The individual galaxy luminosity functions (GLFs) of red sequence
galaxies were studied in the five ugriz bands for 48 clusters. The GLFs were
then stacked in three mass bins and two redshift bins. Twenty clusters of the
present sample are studied for the first time in X-rays, and all are studied
for the first time in the optical range. Altogether, our sample appears to have
X-ray and optical properties typical of average cluster properties.Comment: accepted for publications in MNRA
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