80 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
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
The distant galaxy cluster CL0016+16: X-ray analysis up to
To study the mass distribution of galaxy clusters up to their Virial radius,
CL0016+16 seems to be a good candidate,since it is a bright massive cluster,
previously considered as being dynamically relaxed. Using XMM-Newton
observations of CL0016+16, we performed a careful X-ray background analysis,
and we detected convincingly its X-ray emission up to . We then
studied its dynamical state with a detailed 2D temperature and surface
brightness analysis of the inner part of the cluster. Using the assumption of
both spherical symmetry and hydrostatic equilibrium (HE) we can determine the
main cluster parameters: total mass, temperature profile, surface brightness
profile and -parameter. We also build a temperature map which clearly
exhibits departure from spherical symmetry in the centre. To estimate the
influence of these perturbations onto our total mass estimate, we also compute
the total mass in the framework of the HE approach, but this time with various
temperature profiles obtained in different directions. These various total mass
estimates are consistent with each other. The temperature perturbations are
clear signatures of ongoing merger activity. We also find significant residuals
after subtracting the emissivity map by a 2D -model fit. We conclude
that, although CL0016+16 shows clear signs of merger activity and departure
from spherical symmetry in the centre, its X-ray emissivity can be detected up
to and the corresponding mass can be computed directly. It
is therefore a good candidate to study cosmological scaling laws as predicted
by the theory.Comment: 11 pages, 17 figures, Accepted for publication in A&
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
XMM-Newton spectral analysis of the Pulsar Wind Nebula within the composite SNR G0.9+0.1
We present a study of the composite supernova remnant G0.9+0.1 based on
observations by XMM-Newton. The EPIC spectrum shows diffuse X-ray emission from
the region corresponding to the radio shell. The X-ray spectrum of the whole
Pulsar Wind Nebula is well fitted by an absorbed power-law model with a photon
index Gamma ~ 1.9 and a 2-10 keV luminosity of about 6.5 X 10^34 d^2_10 erg
s^-1 (d_10 is the distance in units of 10 kpc). However, there is a clear
softening of the X-ray spectrum with distance from the core, which is most
probably related to the finite lifetime of the synchrotron emitting electrons.
This is fully consistent with the plerionic interpretation of the Pulsar Wind
Nebula, in which an embedded pulsar injects energetic electrons into its
surrounding region. At smaller scales, the eastern part of the arc-like
feature, which was first revealed by Chandra observations, shows indications of
a hard X-ray spectrum with a corresponding small photon index (Gamma=1.0 +-
0.7), while the western part presents a significantly softer spectrum
(Gamma=3.2 +- 0.7). A possible explanation for this feature is fast rotation
and subsequent Doppler boosting of electrons: the eastern part of the torus has
a velocity component pointing towards the observer, while the western part has
a velocity component in the opposite direction pointing away from the observer.Comment: 8 pages, 7 figures, A&A in pres
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
The dynamical state of the Coma cluster with XMM-Newton
We present in this paper a substructure and spectroimaging study of the Coma
cluster of galaxies based on XMM-Newton data. XMM-Newton performed a mosaic of
observations of Coma to ensure a large coverage of the cluster. We add the
different pointings together and fit elliptical beta-models to the data. We
subtract the cluster models from the data and look for residuals, which can be
interpreted as substructure. We find several significant structures: the
well-known subgroup connected to NGC4839 in the South-West of the cluster, and
another substructure located between NGC 4839 and the centre of the Coma
cluster. Constructing a hardness ratio image, which can be used as a
temperature map we see that in front of this new structure the temperature is
significantly increased (higher or equal 10 keV). We interpret this temperature
enhancement as the result of heating as this structure falls onto the Coma
cluster. We furthermore reconfirm the filament-like structure South-East of the
cluster centre. This region is significantly cooler than the mean cluster
temperature. We estimate the temperature of this structure to be equal or below
1keV. A possible scenario to explain the observed features is stripping caused
by the infall of a small group of galaxies located around the two galaxies
NGC4921 and NGC4911 into the Coma cluster with a non-zero impact parameter. We
also see significant X-ray depressions North and South-East of NGC4921, which
might either be linked to tidal forces due to the merger with the Western
structure or connected to an older cluster merger.Comment: 12 pages, 4 figures accepted for publication in A&
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