97 research outputs found
XMM-Newton observations of the Coma cluster relic 1253+275
Using XMM Newton data, we investigate the nature of the X-ray emission in the
radio relic 1253+275 in the Coma cluster. We determine the conditions of the
cluster gas to check current models of relic formation, and we set constraints
on the intracluster magnetic field. Both imaging and spectral analysis are
performed, and the X-ray emission is compared with the radio emission. We found
that the emission is of thermal origin and is connected to the sub-group around
NGC 4839. The best-fit gas temperature in the region of the relic and in its
vicinity is in the range 2.8 - 4.0 keV, comparable to the temperature of the
NGC 4839 sub-group. We do not detect any high temperature gas, resulting from a
possible shock in the region of the Coma relic. We therefore suggest that the
main source of energy for particles radiating in the radio relic is likely to
be turbulence. From the X-ray data, we can also set a flux upper limit of 3.2 x
10e-13 erg/cm^2 s, in the 0.3 - 10 keV energy range, to the non-thermal
emission in the relic region. This leads to a magnetic field B > 1.05 microG.Comment: 4 pages, 2 figures, Accepted for publication in A&A Letter
Measuring Cluster Temperature Profiles with XMM/EPIC
Using the PV observation of A1795, we illustrate the capability of XMM-EPIC
to measure cluster temperature profiles, a key ingredient for the determination
of cluster mass profiles through the equation of hydrostatic equilibrium. We
develop a methodology for spatially resolved spectroscopy of extended sources,
adapted to XMM background and vignetting characteristics. The effect of the
particle induced background is discussed. A simple unbiased method is proposed
to correct for vignetting effects, in which every photon is weighted according
to its energy and location on the detector. We were able to derive the
temperature profile of A1795 up to 0.4 times the virial radius. A significant
and spatially resolved drop in temperature towards the center (r<200 kpc) is
observed, which corresponds to the cooling flow region of the cluster. Beyond
that region, the temperature is constant with no indication of a fall-off at
large radii out to 1.2 Mpc.Comment: 7 pages, 8 figures, Accepted for publication in A&A (special Letter
issue on XMM
Spatially resolved X-ray spectroscopy and modeling of the nonthermal emission of the PWN in G0.9+0.1
We performed a spatially resolved spectral X-ray study of the pulsar wind
nebula (PWN) in the supernova remnant G0.9+0.1. Furthermore we modeled its
nonthermal emission in the X-ray and very high energy (VHE, E > 100 GeV)
gamma-ray regime. Using Chandra ACIS-S3 data, we investigated the east-west
dependence of the spectral properties of G0.9+0.1 by calculating hardness
ratios. We analyzed the EPIC-MOS and EPIC-pn data of two on-axis observations
of the XMM-Newton telescope and extracted spectra of four annulus-shaped
regions, centered on the region of brightest emission of the source. A radially
symmetric leptonic model was applied in order to reproduce the observed X-ray
emission of the inner part of the PWN. Using the optimized model parameter
values obtained from the X-ray analysis, we then compared the modeled inverse
Compton (IC) radiation with the published H.E.S.S. gamma-ray data. The spectral
index within the four annuli increases with growing distance to the pulsar,
whereas the surface brightness drops. With the adopted model we are able to
reproduce the characteristics of the X-ray spectra. The model results for the
VHE gamma radiation, however, strongly deviate from the H.E.S.S. data.Comment: 8 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
The XMM-Newton Project
The abundance of high-redshift galaxy clusters depends sensitively on the
matter density \OmM and, to a lesser extent, on the cosmological constant
. Measurements of this abundance therefore constrain these fundamental
cosmological parameters, and in a manner independent and complementary to other
methods, such as observations of the cosmic microwave background and distance
measurements. Cluster abundance is best measured by the X-ray temperature
function, as opposed to luminosity, because temperature and mass are tightly
correlated, as demonstrated by numerical simulations. Taking advantage of the
sensitivity of XMM-Newton, our Guaranteed Time program aims at measuring the
temperature of the highest redshift (z>0.4) SHARC clusters, with the ultimate
goal of constraining both \OmM and .Comment: To appear in the Proceedings of the XXI Moriond Conference: Galaxy
Clusters and the High Redshift Universe Observed in X-rays, edited by D.
Neumann, F. Durret, & J. Tran Thanh Va
XMM-Newton observation of the most X-ray-luminous galaxy cluster RX J1347.5-1145
We report on an XMM-Newton observation of RX J1347.5-1145 (z=0.451), the most
luminous X-ray cluster of galaxies currently known, with a luminosity L_X = 6.0
\pm 0.1 \times 10^45 erg/s in the [2-10] keV energy band. We present the first
temperature map of this cluster, which shows a complex structure. It identifies
the cool core and a hot region at radii 50-200 kpc to south-east of the main
X-ray peak, at a position consistent with the subclump seen in the X-ray image.
This structure is probably an indication of a submerger event. Excluding the
data of the south-east quadrant, the cluster appears relatively relaxed and we
estimate a total mass within 1.7 Mpc of 2.0 \pm 0.4 \times 10^15 M_sun. We find
that the overall temperature of the cluster is kT=10.0 \pm 0.3 keV. The
temperature profile shows a decline in the outer regios and a drop in the
centre, indicating the presence of a cooling core which can be modelled by a
cooling flow model with a minimum temperature ~2 keV and a very high mass
accretion rate, \dot{M} ~ 1900 M_sun/yr. We compare our results with previous
observations from ROSAT, ASCA and Chandra.Comment: 4 pages, 6 figures, accepted for publication in Astronomy &
Astrophysics Letter
RXJ0256.5+0006: a merging cluster of galaxies at z=0.36 observed with XMM-Newton
(abridged) We present a study based on XMM data of RX J0256.5+0006, a medium
distant (z=0.36) galaxy cluster found in the Bright SHARC catalog. The
intracluster medium shows a bimodal structure: one main cluster component and a
substructure in the west. Despite the indication of interaction we do not find
any sign of temperature gradients. Due to the non-symmetric form of the main
cluster we extract surface brightness profiles in different sectors around its
centre. We see large variations between the profiles, which we quantify by
beta-model fitting. The corresponding r_c's vary between 0.1-0.5Mpc and the
beta's between 0.5-1.2. The variations of the beta-model parameters indicate
that the main cluster is not entirely relaxed. This hypothesis is strengthened
by the fact that the cluster is over-luminous with respect to the (z-evolving)
L_x-T relation found for nearby clusters. Comparing our profiles to the
reference emission measure profile of Arnaud et al., we find that only the
profile extracted north-east (NE) of the main cluster centre is similar to this
reference profile. This indicates that only the NE profile is representative
for the relaxed part of this cluster component. Using this profile and the
spectroscopically fitted temperature of T=4.9^+0.5_-0.4keV we find M_500~4
10^14 solar masses. This value is in agreement with the value obtained using
the z-evolving M_500-T relation from the HIFLUGCS sample. For the gas mass
fraction we find f_g~18-20% which is in good agreement with other work. We also
develop a simple on-axis merger model for the cluster. Together with a simple
ram pressure model we find that the most likely physical distance of the
subcluster to the main cluster lies between 0.6<d<1.0Mpc. We find for the ratio
of subcluster to main cluster mass values between 20-30%.Comment: 19 pages including 19 figures (including 4 figures in jpg and png
format), accepted for publication in A&
XMM-Newton observation of Abell 1835 : temperature, mass and gas mass fraction profiles
We present a study of the medium distant cluster of galaxies Abell 1835 based
on XMM-Newton data. The high quality of XMM-Newton data enable us to perform
spectro-imaging of the cluster up to large radii. We determine the gas and
total mass profiles based on the hydrostatic approach using the beta-model and
the temperature profile. For the determination of the temperature profile of
the ICM, which is needed for the mass determination, we apply a double
background subtraction, which accounts for the various kinds of background
present (particle and astrophysical background). We find a basically flat
temperature profile up to 0.75 r_200 with a temperature decrease towards the
center linked to the cooling flow. We obtain a gas mass fraction of (20.7 +/-
3.7)%, which is a lower limit on the baryon fraction in this cluster. Using
this value as baryon fraction for the entire universe, we obtain by combining
our results with results based on primordial nucleosynthesis, an upper limit
for Omega_m < 0.5h_{50}^{-1/2}, which is in good agreement with other recent
studies.Comment: 12 pages, 16 figures and 3 tables, accepted for publication in
Astronomy & Astrophysic
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