1,449 research outputs found
Chandra Observation of Abell 2065: An Unequal Mass Merger?
We present an analysis of a 41 ks Chandra observation of the merging cluster
Abell 2065 with the ACIS-I detector. Previous observations with ROSAT and ASCA
provided evidence for an ongoing merger, but also suggested that there were two
surviving cooling cores, which were associated with the two cD galaxies in the
center of the cluster. The Chandra observation reveals only one X-ray surface
brightness peak, which is associated with the more luminous, southern cD
galaxy. The gas related with that peak is cool and displaced slightly from the
position of the cD. The data suggest that this cool material has formed a cold
front. On the other hand, in the higher spatial resolution Chandra image, the
second feature to the north is not associated with the northern cD; rather, it
appears to be a trail of gas behind the main cD. We argue that only one of the
two cooling cores has survived the merger, although it is possible that the
northern cD may not have possessed a cool core prior to the merger. We use the
cool core survival to constrain the kinematics of the merger and we find an
upper limit of ~< 1900 km/s for the merger relative velocity. A surface
brightness discontinuity is found at ~140 kpc from the southern cD; the Mach
number for this feature is , although its
nature (shock or cold front) is not clear from the data. We argue that Abell
2065 is an example of an unequal mass merger. The more massive southern cluster
has driven a shock into the ICM of the infalling northern cluster, which has
disrupted the cool core of the latter, if one existed originally. We estimate
that core crossing occurred a few hundred Myr ago, probably for the first time.Comment: 15 pages, 10 figures, ApJ in pres
XMM-Newton Observation of the Northwest Radio Relic Region in Abell 3667
Abell 3667 is the archetype of a merging cluster with radio relics. The NW
radio relic is the brightest cluster relic or halo known, and is believed to be
due to a strong merger shock. We have observed the NW relic for 40 ksec of net
XMM time. We observe a global decline of temperature across the relic from 6 to
1 keV, similar to the Suzaku results. Our new observations reveal a sharp
change of both temperature and surface brightness near the position of the
relic. The increased X-ray emission on the relic can be equivalently well
described by either a thermal or nonthermal spectral model. The parameters of
the thermal model are consistent with a Mach number M~2 shock and a shock speed
of ~1200 km s^-1. The energy content of the relativistic particles in the radio
relic can be explained if they are (re)-accelerated by the shock with an
efficiency of ~0.2%. Comparing the limit on the inverse Compton X-ray emission
with the measured radio synchrotron emission, we set a lower limit to the
magnetic field in the relic of 3 muG. If the emission from the relic is
non-thermal, this lower limit is in fact the required magnetic field.Comment: 11 pages, ApJ in pres
WQ 2059-247: An unusual high redshift X-ray cluster
X-ray, optical, and radio observations of a high redshift, Bautz-Morgan type I cluster of galaxies are reported. The cD galaxy contains a powerful, flat spectrum radio source coincident with the possibly stellar nucleus. The cluster is an extremely luminous X-ray source; however, unlike nearby luminous X-ray clusters the X-ray spectrum appears to be rather soft. Two possible interpretations of the soruces are suggested: either the intracluster gas is much cooler in high redshift clusters because they are less relaxed, or the X-ray and radio emissions from WQ 2059-247 are the result of a non thermal QSO/BL Lac type object in the nucleus of the cD
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