ﻻ يوجد ملخص باللغة العربية
We use Chandra data to derive a detailed gas temperature map of the nearby, hot, merging galaxy cluster A754. Combined with the X-ray and optical images, the map reveals a more complex merger geometry than previously thought, possibly involving more than two subclusters or a cool gas cloud sloshing independently from its former host subcluster. In the cluster central region, we detect spatial variations of the gas temperature on all linear scales, from 100 kpc (the map resolution) and up, which likely remain from a merger shock passage. These variations are used to derive an upper limit on effective thermal conductivity on a 100 kpc scale, which is at least an order of magnitude lower than the Spitzer value. This constraint pertains to the bulk of the intracluster gas, as compared to the previously reported estimates for cold fronts (which are rather peculiar sites). If the conductivity in a tangled magnetic field is at the recently predicted higher values (i.e., about 1/5 of the Spitzer value), the observed suppression can be achieved, for example, if the intracluster gas consists of magnetically isolated domains.
To better understand the mechanism or mechanisms that lead to AGN activity today, we measure the X-ray AGN fraction in a new sample of nearby clusters and examine how it varies with galaxy properties, projected cluster-centric radius, and cluster vel
We present a long BeppoSAX observation of Abell 754 that reports a nonthermal excess with respect to the thermal emission at energies greater than ~45 keV. A VLA radio observation at 1.4 GHz definitely confirms the existence of diffuse radio emission
To investigate the present situation of the merging in the southern outer region of Abell 85, we carried out long (~100 ks) observations with Suzaku, and produced an X-ray hardness ratio map. We found a high hardness ratio peak in the east side of a
We have analyzed the Chandra, BeppoSax, and ROSAT observations of Abell 754 and report evidence of a soft, diffuse X-ray component. The emission is peaked in the cluster center and is detected out to 8 from the X-ray center. Fitting a thermal model t
In this paper we investigate, by means of two-dimensional magnetohydrodynamic simulations, the impact of temperature-dependent resistivity and thermal conduction on the development of plasmoid instabilities in reconnecting current sheets in the solar