Issue |
A&A
Volume 413, Number 2, January II 2004
|
|
---|---|---|
Page(s) | 415 - 439 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20031512 | |
Published online | 18 December 2003 |
Spatially resolved X-ray spectroscopy of cooling clusters of galaxies
1
SRON National Institute for Space Research Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
2
Department of Physics, Columbia University, 550 West 120th Street, New York, NY 10027, USA
3
Paul Scherrer Institute, Laboratory for Astrophysics, 5232 Villigen, Switzerland
4
Institute of Theoretical Physics, University of Zürich, Winterthurerstrasse, 190, 8057 Zürich, Switzerland
5
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
6
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
Corresponding author: J.S. Kaastra, J.Kaastra@sron.nl
Received:
8
January
2003
Accepted:
22
September
2003
We present spatially resolved X-ray spectra taken with the EPIC cameras of
XMM-Newton of a sample of 17 cooling clusters and three non-cooling clusters for
comparison. The deprojected spectra are analyzed with a multi-temperature
model, independent of any a priori assumptions about the physics behind the
cooling and heating mechanisms. All cooling clusters show a central decrement
of the average temperature, most of them of a factor of . Three
clusters (Sérsic 159-3, MKW 3s and Hydra A) only show a weak temperature
decrement, while two others (A 399 and A 2052) have a very strong temperature
decrement. All cooling clusters show a weak pressure gradient in the core.
More important, at each radius within the cooling region the gas is not
isothermal. The differential emission measure distribution shows a strong peak
near the maximum (ambient) temperature, with a steep decline towards lower
temperatures, approximately proportional to T3, or alternatively a cut-off
at about a quarter to half of the maximum temperature. In general, we find a
poor correlation between radio flux of the central galaxy and the temperature
decrement of the cooling flow. This is interpreted as evidence that except for
a few cases (like the Hydra A cluster) heating by a central AGN is not the most
common cause of weak cooling flows. We investigate the role of heat conduction
by electrons and find that the theoretically predicted conductivity rates are
not high enough to balance radiation losses. The differential emission measure
distribution has remarkable similarities with the predictions from coronal
magnetic loop models. Also the physical processes involved (radiative cooling,
thermal conduction along the loops, gravity) are similar for clusters loops and
coronal loops. If coronal loop models apply to clusters, we find that a few
hundred loops per scale height should be present. The typical loop sizes
deduced from the observed emission measure distribution are consistent with the
characteristic magnetic field sizes deduced from Faraday rotation measurements.
Key words: galaxies: clusters: general / cooling flows / X-rays: galaxies: clusters
© ESO, 2004
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