Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chandra observtaion of A2256 - a cluster at the early stage of merging   We present here \chandra observations of the rich cluster of galaxies A2256.
In addition to the known cool subcluster, a new structure was resolved 2$'$
east of the peak of the main cluster. Its position is roughtly at the center of
a low-brightness radio halo. Spectral analysis shows that the "shoulder" has
high iron abundance ($\sim$ 1). We suggest that this structure is either
another merging component or an internal structure of the main cluster. The
X-ray redshifts of several regions were measured. The results agree with the
optical ones and suggest that the main cluster, the subcluster and the
"shoulder" are physically associated and interacting. The subcluster has low
temperature ($\sim$ 4.5 keV) and high iron abundance ($\sim$ 0.6) in the
central 150 kpc. The \chandra image shows a relatively sharp brightness
gradient at the south of the subcluster peak running south-south-east (SSE). A
temperature jump was found across the edge, with higher temperature ahead of
the edge in the low density region. This phenomenon is qualitatively similar to
the "cold fronts" found in A2142 and A3667. If the "shoulder" is ignored, the
temperature map resembles those simulations at the early stage of merging while
the subcluster approached the main cluster from somewhere west. This fact and
the observed edge, in combination with the clear iron abundance contrast
between the center of the subcluster ($\sim$ 0.6) and the main cluster ($\sim$
0.2), all imply that the ongoing merger is still at the early stage. At least
three member galaxies, including a radio head-tail galaxy, were found to have
corresponding X-ray emission.

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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat