Free access article
| Issue |
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A&A
Volume 443,
Number 1,
November III 2005
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Page(s)
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29 - 39 |
| Section |
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Cosmology (including clusters of galaxies) |
| DOI |
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10.1051/0004-6361:20053169 |
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A&A 443, 29-39 (2005)
DOI: 10.1051/0004-6361:20053169
ROSAT observations of the soft X-ray background and of the cluster
soft excess emission in the Hercules supercluster
M. Bonamente1, 2, R. Lieu2 and J. Kaastra3 1
NASA National Space Science Technology Center, Huntsville, AL, USA
e-mail: bonamem@uah.edu
2
Department of Physics, University of Alabama,
Huntsville, AL, USA
e-mail: lieur@cspar.uah.edu
3
SRON, Utrecht, The Netherlands
e-mail: J.S.Kaastra@sron.nl
(Received 1 April 2005 / Accepted 28 July 2005)
Abstract
Recent observations with the XMM-Newton satellite confirmed the
existence of the soft excess phenomenon in galaxy clusters, earlier discovered
in several EUVE, ROSAT and BeppoSAX observations. Among the clusters for which XMM has
reported detection of
soft excess emission are MKW03s and A2052, two clusters in the Hercules concentration.
The Hercules supercluster lies along the southern extension of the North
Polar Spur, a region of bright soft X-ray emission clearly visible in
ROSAT All-Sky Survey images.
We analyze 11 pointed ROSAT PSPC observations toward 3 clusters in the
Hercules concentration, MKW03s, A2052 and A2063, and 8 neighboring fields in
order to investigate the soft X-ray emission in that region of the sky.
We find that the soft X-ray emission varies by a factor of few on scales of few
degrees, rendering the background subtraction a complex task.
If the North Polar Spur emission is of local origin, we find that only A2052 and
A2063 have evidence of cluster soft excess emission, and that the OVII emission
lines detected in XMM observations of A2052 and MKW03s are not associated
with the cluster.
If part or all of the North Polar Spur soft X-ray enhancement is of extragalactic nature,
the three clusters feature strong soft excess emission, and the OVII emission lines
observed by XMM are genuinely associated with the clusters.
We interpret the soft excess emission with the presence of warm gas, either intermixed with
the hot intra-cluster medium or in filamentary structures located around the clusters,
and estimate that the warm gas is approximately as massive as the hot intra-cluster medium.
Key words: galaxies: clusters: individual: MKW03s, A2052, A2063
-- X-rays: galaxies: clusters
SIMBAD Objects
© ESO 2005
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