75 research outputs found
Metal distribution in sloshing galaxy clusters: the case of A496
We report results from a detailed study of the sloshing gas in the core of
A496. We detect the low temperature/entropy spiral feature found in several
cores, we also find that conduction between the gas in the spiral and the
ambient medium must be suppressed by more than one order of magnitude with
respect to Spitzer conductivity. Intriguingly, while the gas in the spiral
features a higher metal abundance than the surrounding medium, it follows the
entropy vs metal abundance relation defined by gas lying outside the spiral.
The most plausible explanation for this behavior is that the low entropy metal
rich plasma uplifted through the cluster atmosphere by sloshing, suffers little
heating or mixing with the ambient medium. While sloshing appears to be capable
of uplifting significant amounts of gas, the limited heat exchange and mixing
between gas in and outside the spiral implies that this mechanism is not at all
effective in: 1) permanently redistributing metals within the core region and
2) heating up the coolest and densest gas, thereby providing little or no
contribution to staving of catastrophic cooling in cool cores.Comment: Accepted for publication on A&
SMAUG: a new technique for the deprojection of galaxy clusters
This paper presents a new technique for reconstructing the spatial
distributions of hydrogen, temperature and metal abundance of a galaxy cluster.
These quantities are worked out from the X-ray spectrum, modeled starting from
few analytical functions describing their spatial distributions. These
functions depend upon some parameters, determined by fitting the model to the
observed spectrum. We have implemented this technique as a new model in the
XSPEC software analysis package. We describe the details of the method, and
apply it to work out the structure of the cluster A1795. We combine the
observation of three satellites, exploiting the high spatial resolution of
Chandra for the cluster core, the wide collecting area of XMM-Newton for the
intermediate regions and the large field of view of Beppo-SAX for the outer
regions. We also test the validity and precision of our method by i) comparing
its results with those from a geometrical deprojection, ii) examining the
spectral residuals at different radii of the cluster and iii) reprojecting the
unfolded profiles and comparing them directly to the measured quantities. Our
analytical method yields the parameters defining the spatial functions directly
from the spectra. Their explicit knowledge allows a straightforward derivation
of other indirect physical quantities like the gravitating mass, as well as a
fast and easy estimate of the profiles uncertainties.Comment: 24 pages, 11 figures, 3 tables; emulateapj; accepted for publication
in the Astrophysical Journa
The correlation function of X-ray galaxy clusters in the RASS1 Bright Sample
We analyse the spatial clustering properties of the RASS1 Bright Sample, an
X-ray flux-limited catalogue of galaxy clusters selected from the southern part
of the All-Sky Survey. The two-point correlation function of
the whole sample is well fitted (in an Einstein-de Sitter model) by the
power-law , with Mpc
and (95.4 per cent confidence level with one
fitting parameter). We use the RASS1 Bright Sample as a first application of a
theoretical model which aims at predicting the clustering properties of X-ray
clusters in flux-limited surveys for different cosmological scenarios. The
model uses the theoretical and empirical relations between mass, temperature
and X-ray cluster luminosity, and fully accounts for the redshift evolution of
the underlying dark matter clustering and cluster bias factor. The comparison
between observational results and theoretical predictions shows that the
Einstein-de Sitter models display too low a correlation length, while models
with a matter density parameter (with or without a
cosmological constant) are successful in reproducing the observed clustering.
The dependence of the correlation length on the X-ray limiting flux and
luminosity of the sample is generally consistent with the predictions of all
our models. Quantitative agreement is however only reached for models. The model presented here can be reliably applied to future
deeper X-ray cluster surveys: the study of their clustering properties will
provide a useful complementary tool to the traditional cluster abundance
analyses to constrain the cosmological parameters.Comment: 11 pages, Latex using MN style, 4 figures enclosed. Version accepted
for publication in MNRA
A note on Temperature Profiles of rich Clusters of Galaxies
We derive here the mean temperature profile for a sample of hot, medium
distant clusters recently observed with XMM-Newton, whose profiles are
available from the literature, and compare it with the mean temperature profile
found from BeppoSAX data. The XMM-Newton and BeppoSAX profiles are in good
agreement between 0.05 and 0.25 r_180. From 0.25 to about 0.5 r_180 both
profiles decline, however the BeppoSAX profile does so much more rapidly than
the XMM-Newton profile.Comment: 3 pages, 2 figures included. Proceedings of IAU Colloquium n.195 -
Outskirts of Galaxy Clusters: intense life in the suburb
- …