220 research outputs found
The warm interstellar medium around the Cygnus Loop
Observations of the oxygen lines [OII]3729 and [OIII]5007 in the medium
immediately beyond the Cygnus Loop supernova remnant were carried out with the
scanning Fabry-P\'erot spectrophotometer ESOP. Both lines were detected in
three different directions - east, northeast and southwest - and up to a
distance of 15 pc from the shock front. The ionized medium is in the immediate
vicinity of the remnant, as evinced by the smooth brightening of both lines as
the adiabatic shock transition (defined by the X-ray perimeter) is crossed.
These lines are usually brighter around the Cygnus Loop than in the general
background in directions where the galactic latitude is above 5 degrees. There
is also marginal (but significant) evidence that the degree of ionization is
somewhat larger around the Cygnus Loop. We conclude that the energy necessary
to ionize this large bubble of gas could have been supplied by an O8 or O9 type
progenitor or the particles heated by the expanding shock front. The second
possibility, though highly atractive, would have to be assessed by extensive
modelling.Comment: 18 pages, 8 figures, ApJ 512 in pres
XMM -Newton observations of merging clusters of galaxies: A3921 and A1750
We show the XMM-Newton guaranted time observations of 2 clusters of galaxies
in a different stage of merger.Comment: 4 pages, LaTex, 9 figures. To appear in the Proceedings of the
Conference "New Visions of the X-ray Universe in the XMM-Newton and Chandra
era" -ESTEC - Noordwijk, The Netherlands, Nov 200
XMM-Newton observations of the supernova remnant RX J1713.7-3946 and its central source
We present new results from the observations of the supernova remnant (SNR) RX J1713.7–3946 (also G347.3–0.5) performed in five distinct pointings with the EPIC instrument on board the satellite XMM-Newton. RX J1713.7–3946 is a shelltype
SNR dominated by synchrotron radiation in the X-rays. Its emission (emission measure and photon index) as well as the absorption along the line-of-sight has been characterized over the entire SNR. The X-ray mapping of the absorbing column density has revealed strong well-constrained variations (0.4 × 1022 cm−2 ≤ NH ≤ 1.1 × 1022 cm−2) and, particularly, a strong absorption in the southwest. Moreover, there are several clues indicating that the shock front of RX J1713.7–3946 is impacting the clouds responsible for the absorption as revealed for instance by the positive correlation between X-ray absorption and X-ray brightness along the western rims. The CO and H observations show that the inferred cumulative absorbing column densities are in excellent agreement with the X-ray findings in different parts of the remnant on condition that the SNR lies at a distance of 1.3 ± 0.4 kpc, probably in the Sagittarius galactic arm, instead of the commonly-accepted value of 6 kpc. An excess in the CO emission is found in the southwest suggesting that the absorption is due to molecular clouds. A search for OH masers in the southwestern region has been unsuccessful, possibly due to the low density of the clouds. The X-ray mapping of the photon index has also revealed strong variations (1.8 ≤ Γ ≤ 2.6). The spectrum is steep in the faint central regions and
flat at the presumed shock locations, particularly in the southeast. Nevertheless, the regions where the shock impacts molecular clouds have a steeper spectrum than those where the shock propagates into a low density medium. The search for the thermal emission in RX J1713.7–3946 has been unsuccessful leading to a number density upper limit of 2 × 10−2 cm−3 in the ambient medium. This low density corresponds to a reasonable kinetic energy of the explosion provided that the remnant is less than a few thousand years old. A scenario based on a modified ambient medium due to the effect of a progenitor stellar wind is proposed and leads to an estimate of RX J1713.7–3946’s progenitor mass between 12 and 16 M. The X-ray bright central point source 1WGA J1713.4–3949 detected at the center of SNR RX J1713.7–3946 shows spectral properties very similar to those of the Compact Central Objects found in SNRs and consistent in terms of absorption with that of the central diffuse X-ray emission arising from the SNR. It is highly probable that the point source 1WGA J1713.4–3949 is the compact relic of RX J1713.7–3946’s supernova progenitor.Fil: Cassam Chenaï, G.. Centre D; FranciaFil: Decourchelle, A.. Centre D; FranciaFil: Ballet, J.;. Centre D; FranciaFil: Sauvageot, J. L.. Centre D; FranciaFil: Dubner, Gloria Mabel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Giacani, Elsa Beatriz. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
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&
XMM-Newton observation of SNR RX J1713.7-3946
We present the first results of the observations of the supernova remnant RX
J1713.7-3946 (also G347.3-0.5) obtained with the EPIC instrument on board the
XMM-Newton satellite. We show a 5 pointings mosaiced image of the X-ray
synchrotron emission. We characterize this emission by mapping its spectral
parameters (absorbing column density NH and photon index). The synchrotron
spectrum is flat at the shock and steep in the interior of the remnant. NH is
well correlated with the X-ray brightness. A strong NH is found in the
southwest rim of RX J1713.7-3946. We suggest that the SNR is interacting with a
HI region there.Comment: 4 pages, 4 figures, To appear in "Young Neutron Stars and Their
Environments" (IAU Symposium 218, ASP Conference Proceedings), eds F. Camilo
and B. M. Gaensle
A noncommutative Sierpinski gasket
A quantized version of the Sierpinski gasket is proposed, on purely topological grounds, as a C*-algebra A infinity with a suitable form of self-similarity. Several properties of A infinity are studied, in particular its nuclearity, the structure of ideals as well as the description of irreducible representations and extremal traces. A harmonic structure is introduced, giving rise to a self-similar Dirichlet form E. A spectral triple is also constructed, extending the one already known for the classical gasket, from which E can be reconstructed. Moreover we show that A infinity is a compact quantum metric space
A2163: Merger events in the hottest Abell galaxy cluster II. Subcluster accretion with galaxy-gas separation
Located at z = 0.203, A2163 is a rich galaxy cluster with an intra-cluster
medium (ICM) that exhibits extraordinary properties, including an exceptionally
high X-ray luminosity, average temperature, and a powerful and extended radio
halo. The irregular and complex morphology of its gas and galaxy structure
suggests that this cluster has recently undergone major merger events that
involve two or more cluster components. In this paper, we study the gas
structure and dynamics by means of spectral-imaging analysis of X-ray data
obtained from XMM-Newton and Chandra observations. From the evidence of a cold
front, we infer the westward motion of a cool core across the E-W elongated
atmosphere of the main cluster A2163-A. Located close to a galaxy over-density,
this gas 'bullet' appears to have been spatially separated from its galaxy (and
presumably dark matter component) as a result of high-velocity accretion.
From gas brightness and temperature profile analysis performed in two
opposite regions of the main cluster, we show that the ICM has been
adiabatically compressed behind the crossing 'bullet' possibly because of shock
heating, leading to a strong departure of the ICM from hydrostatic equilibrium
in this region. Assuming that the mass estimated from the Yx proxy best
indicates the overall mass of the system and that the western cluster sector is
in approximate hydrostatic equilibrium before subcluster accretion, we infer a
merger scenario between two subunits of mass ratio 1:4, leading to a present
total system mass of M500 . The exceptional
properties of A2163 present various similarities with those of 1E0657-56, the
so-called 'bullet-cluster'. These similarities are likely to be related to a
comparable merger scenario.Comment: A&A, in pres
Merging clusters of galaxies observed with XMM-Newton
We present results from the XMM-Newton observations of our ongoing program on
merging clusters. To date three clusters have been observed, covering the
temporal sequence from early to late stage mergers: A1750, A2065 and A3921.
Using spatially-resolved spectroscopy of discrete regions, hardness ratio and
temperature maps, we show that all three clusters display a complex temperature
structure. In the case of A1750, a double cluster, we argue that the observed
temperature structure is not only related to the ongoing merger but also to
previous merger events. A2065 seems an excellent example of a `compact merger',
i.e. when the centres of the two clusters have just started to interact,
producing a shock in the ICM. Using comparisons with numerical simulations and
complementary optical data, the highly complex temperature structure evident in
A3921 is interpreted as an off-axis merger between two unequal mass components.
These results illustrate the complex physics of merger events. The relaxation
time can be larger than the typical time between merger events, so that the
present day morphology of clusters depends not only on on-going interaction but
also on the more ancient formation history.Comment: 10 pages, 3 figures. Use elsart.cls. Accepted for publication in
Advances in Space Research. A version with full resolution figures can be
found at http://www.star.bris.ac.uk/elena/cospar_3clusters.pd
SIMBOL-X : a new generation hard X-ray telescope
SIMBOL-X is a hard X-ray mission, operating in the 0.5-70 keV range, which is
proposed by a consortium of European laboratories for a launch around 2010.
Relying on two spacecraft in a formation flying configuration, SIMBOL-X uses a
30 m focal length X-ray mirror to achieve an unprecedented angular resolution
(30 arcsec HEW) and sensitivity (100 times better than INTEGRAL below 50 keV)
in the hard X-ray range. SIMBOL-X will allow to elucidate fundamental questions
in high energy astrophysics, such as the physics of accretion onto Black Holes,
of acceleration in quasar jets and in supernovae remnants, or the nature of the
hard X-ray diffuse emission. The scientific objectives and the baseline
concepts of the mission and hardware design are presented.Comment: 12 pages, 16 fig., Proc. SPIE conf. 5168, San Diego, Aug. 200
- …