760 research outputs found
Temperature structure of the intergalactic medium within seven nearby and bright clusters of galaxies observed with XMM-Newton
Aims. We map the temperature structure of the intra-cluster medium (ICM)
within a nearly complete X-ray flux limited sample of galaxy clusters in the
redshift range z=[0.045,0.096]. Our sample contains seven bright clusters of
galaxies observed with XMM-Newton: Abell 399, Abell 401, Abell 478, Abell 1795,
Abell 2029, Abell 2065, Abell 2256.
Methods. We use a multi-scale spectral mapping algorithm especially designed
to map spectroscopic observables from X-ray extended emission of the ICM.
Derived from a former algorithm using Haar wavelets, our algorithm is now
implemented with B-spline wavelets in order to perform a more regular analysis
of the signal.
Results. For the four clusters in our sample that are major mergers, we find
a complex thermal structure with strong thermal variations consistent with
their dynamics. For two of them, A2065 and A2256, we perform a 3-d analysis of
cold front features evidenced from the gas temperature and brightness maps.
Furthermore, we detect a significant non-radial thermal structure outside the
cool core region of the other 3 more "regular" clusters, with relative
amplitudes of about about 10%. We investigate possible implications of this
structure on the mass estimates of the "regular" clusters A1795 and A2029, by
extracting surface brightness and temperature profiles from sectors
correspondings to the hottest and coldest regions in the maps. While
compensating with surface brightness for A2029, leading to consistent mass
profiles, the temperature structure leads to significant mass discrepancies in
the innermost region of A1795.Comment: published in A&
Shock heating of the merging galaxy cluster A521
A521 is an interacting galaxy cluster located at z=0.247, hosting a low
frequency radio halo connected to an eastern radio relic. Previous Chandra
observations hinted at the presence of an X-ray brightness edge at the position
of the relic, which may be a shock front. We analyze a deep observation of A521
recently performed with XMM-Newton in order to probe the cluster structure up
to the outermost regions covered by the radio emission. The cluster atmosphere
exhibits various brightness and temperature anisotropies. In particular, two
cluster cores appear to be separated by two cold fronts. We find two shock
fronts, one that was suggested by Chandra and that is propagating to the east,
and another to the southwestern cluster outskirt. The two main interacting
clusters appear to be separated by a shock heated region, which exhibits a
spatial correlation with the radio halo. The outer edge of the radio relic
coincides spatially with a shock front, suggesting this shock is responsible
for the generation of cosmic ray electrons in the relic. The propagation
direction and Mach number of the shock front derived from the gas density jump,
M = 2.4 +/- 0.2, are consistent with expectations from the radio spectral
index, under the assumption of Fermi I acceleration mechanism
Pressure profiles of distant galaxy clusters in the Planck catalog
Successive releases of Planck data have demonstrated the strength of the
Sunyaev--Zeldovich (SZ) effect in detecting hot baryons out to the galaxy
cluster peripheries. To infer the hot gas pressure structure from nearby galaxy
clusters to more distant objects, we developed a parametric method that models
the spectral energy distribution and spatial anisotropies of both the Galactic
thermal dust and the Cosmic Microwave Background, that are mixed-up with the
cluster SZ and dust signals. Taking advantage of the best angular resolution of
the High Frequency Instrument channels (5 arcmin) and using X-ray priors in the
innermost cluster regions that are not resolved with Planck, this modelling
allowed us to analyze a sample of 61 nearby members of the Planck catalog of SZ
sources (, ) using the full mission data, as
well as to examine a distant sample of 23 clusters (, ) that have been recently followed-up with XMM-Newton and Chandra
observations. We find that (i) the average shape of the mass-scaled pressure
profiles agrees with results obtained by the Planck collaboration in the nearby
cluster sample, and that (ii) no sign of evolution is discernible between
averaged pressure profiles of the low- and high-redshift cluster samples. In
line with theoretical predictions for these halo masses and redshift ranges,
the dispersion of individual profiles relative to a self-similar shape stays
well below 10 % inside but increases in the cluster outskirts.Comment: 12 pages, 10 figure
Shapley Supercluster Survey: Ram-Pressure Stripping vs. Tidal Interactions in the Shapley Supercluster
We present two new examples of galaxies undergoing transformation in the
Shapley supercluster core. These low-mass (stellar mass from 0.4E10 to 1E10
Msun) galaxies are members of the two clusters SC-1329-313 (z=0.045) and
SC-1327-312 (z=0.049). Integral-field spectroscopy complemented by imaging in
ugriK bands and in Halpha narrow-band are used to disentangle the effects of
tidal interaction (TI) and ram-pressure stripping (RPS). In both galaxies,
SOS-61086 and SOS-90630, we observe one-sided extraplanar ionized gas extending
respectively 30kpc and 41kpc in projection from their disks. The galaxies'
gaseous disks are truncated and the kinematics of the stellar and gas
components are decoupled, supporting the RPS scenario. The emission of the
ionized gas extends in the direction of a possible companion for both galaxies
suggesting a TI. The overall gas velocity field of SOS-61086 is reproduced by
ad hoc N-body/hydrodynamical simulations of RPS acting almost face-on and
starting about 250Myr ago, consistent with the age of the young stellar
populations. A link between the observed gas stripping and the cluster-cluster
interaction experienced by SC-1329-313 and A3562 is suggested. Simulations of
ram pressure acting almost edge-on are able to fully reproduce the gas velocity
field of SOS-90630, but cannot at the same time reproduce the extended tail of
outflowing gas. This suggests that an additional disturbance from a TI is
required. This study adds a piece of evidence that RPS may take place in
different environments with different impacts and witnesses the possible effect
of cluster-cluster merger on RPS.Comment: 27 pages, 28 figures, MNRAS accepte
Aircraft control via variable cant-angle winglets
Copyright @ 2008 American Institute of Aeronautics and AstronauticsThis paper investigates a novel method for the control of "morphing" aircraft. The concept consists of a pair of winglets; with adjustable cant angle, independently actuated and mounted at the tips of a baseline flying wing. The general philosophy behind the concept was that for specific flight conditions such as a coordinated turn, the use of two control devices would be sufficient for adequate control. Computations with a vortex lattice model and subsequent wind-tunnel tests demonstrate the viability of the concept, with individual and/or dual winglet deflection producing multi-axis coupled control moments. Comparisons between the experimental and computational results showed reasonable to good agreement, with the major discrepancies thought to be due to wind-tunnel model aeroelastic effects.This work has been supported by a Marie Curie excellence research grant funded by the European Commission
LoCuSS: Hydrostatic Mass Measurements of the High- Cluster Sample -- Cross-calibration of Chandra and XMM-Newton
We present a consistent analysis of Chandra and XMM-Newton observations of an
approximately mass-selected sample of 50 galaxy clusters at -- the
"LoCuSS High- Sample". We apply the same analysis methods to data from
both satellites, including newly developed analytic background models that
predict the spatial variation of the Chandra and XMM-Newton backgrounds to
and precision respectively. To verify the cross-calibration of
Chandra and XMM-Newton-based cluster mass measurements, we derive the mass
profiles of the 21 clusters that have been observed with both satellites,
extracting surface brightness and temperature profiles from identical regions
of the respective datasets. We obtain consistent results for the gas and total
hydrostatic cluster masses: the average ratio of Chandra- to XMM-Newton-based
measurements of and at are and
, respectively with an intrinsic scatter of for gas
masses and for hydrostatic masses. Comparison of our hydrostatic mass
measurements at with the latest LoCuSS weak-lensing results indicate
that the data are consistent with non-thermal pressure support at this radius
of . We also investigate the scaling relation between our hydrostatic
cluster masses and published integrated Compton parameter
measurements from the Sunyaev-Zel'dovich Array. We measure a scatter in mass at
fixed of at , which is consistent with
theoretical predictions of scatter.Comment: 21 pages, 11 figure
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