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'Sloshing' galaxy cluster discovered

Scientists have spotted vast clouds of hot gas 'sloshing' in Abell 2052, a galaxy cluster situated nearly 480 million light years from Earth.
The scientists are studying the hot (30 million degree) gas using X-ray data from NASA's Chandra X-ray Observatory and optical data from the Very Large Telescope to see the galaxies.

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Abell 2052: A Galaxy Cluster Gets Sloshed

a2052_w1.jpg

Like wine in a glass, vast clouds of hot gas are sloshing back and forth in Abell 2052, a galaxy cluster located about 480 million light years from Earth. X-ray data (blue) from NASA's Chandra X-ray Observatory shows the hot gas in this dynamic system, and optical data (gold) from the Very Large Telescope shows the galaxies. The hot, X-ray bright gas has an average temperature of about 30 million degrees.
A huge spiral structure in the hot gas - spanning almost a million light years - is seen around the outside of the image, surrounding a giant elliptical galaxy at the center. This spiral was created when a small cluster of galaxies smashed into a larger one that surrounds the central elliptical galaxy.

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Title:  A Very Deep Chandra Observation of Abell 2052: Bubbles, Shocks, and Sloshing
Authors: E. L. Blanton (BU), S. W. Randall (CfA), T. E. Clarke (NRL), C. L. Sarazin (UVa), B. R. McNamara (U. Waterloo), E. M. Douglass (BU), M. McDonald (U. Maryland)

We present first results from a very deep (~650 ksec) Chandra X-ray observation of Abell 2052, as well as archival VLA radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by the AGN's radio lobes, compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

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Title: Shocks and Bubbles in a Deep Chandra Observation of the Cooling Flow Cluster Abell 2052
Authors: E. L. Blanton (1), S. W. Randall (2), E. M. Douglass (1), C. L. Sarazin (3), T. E. Clarke (4), B. R. McNamara (5,2,6) ((1) Boston University, (2) Harvard-Smithsonian Centre for Astrophysics, (3) University of Virginia, (4) Naval Research Lab and Interferometrics, Inc., (5) University of Waterloo, (6) Perimeter Institute for Theoretical Physics)

We present results from a deep Chandra observation of Abell 2052. A2052 is a bright, nearby, cooling flow cluster, at a redshift of z=0.035. Concentric surface brightness discontinuities are revealed in the cluster centre, and these features are consistent with shocks driven by the AGN, both with Mach numbers of approximately 1.2. The southern cavity in A2052 now appears to be split into two cavities with the southernmost cavity likely representing a ghost bubble from earlier radio activity. There also appears to be a ghost bubble present to the NW of the cluster centre. The cycle time measured for the radio source is approximately 2 x 10^7 yr using either the shock separation or the rise time of the bubbles. The energy deposited by the radio source, including a combination of direct shock heating and heating by buoyantly rising bubbles inflated by the AGN, can offset the cooling in the core of the cluster.

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Title: Suzaku Observations of the cluster of galaxies Abell 2052
Authors: Takayuki Tamura (ISAS/JAXA), Kazuhisa Mitsuda, Yoh Takei, Noriko Y. Yamasaki, Akiharu ITOH, Kiyoshi Hayashida, J. Patrick Henry, Hideyo Kunieda, Kyoko Matsu****a, Takaya Ohashi

The results from Suzaku XIS observations of the relaxed cluster of galaxies Abell2052 are presented. Offset pointing data are used to estimate the Galactic foreground emission in the direction to the cluster. Significant soft X-ray excess emission above this foreground, the intra-cluster medium emission, and other background components is confirmed and resolved spectroscopically and radially. This excess can be described either by (a) local variations of known Galactic emission components or (b) an additional thermal component with temperature of about 0.2 keV, possibly associated with the cluster. The radial temperature and metal abundance profiles of the intra-cluster medium are measured within ~ 20 in radius (about 60% of the virial radius) from the cluster centre . The temperature drops radially to 0.5-0.6 of the peak value at a radius of  ~ 15'. The gas-mass-weighted metal abundance averaged over the observed region is found to be 0.21 ± 0.05 times solar.

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