Issue |
A&A
Volume 466, Number 2, May I 2007
|
|
---|---|---|
Page(s) | 421 - 435 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20065405 | |
Published online | 29 January 2007 |
Structure and evolution of magnetized clusters: entropy profiles, S – T and LX – T relations
INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio, Italy e-mail: cola@mporzio.astro.it
Received:
10
April
2006
Accepted:
21
December
2006
We study the impact of an intracluster magnetic field on the main structural
properties of clusters and groups of galaxies: the radial density and entropy profiles,
the entropy – temperature relation and the X-ray luminosity – temperature relation for
groups and clusters of galaxies.
To this aim, we develop a description of the intra-cluster gas based on the Hydrostatic
Equilibrium condition and on the Magnetic Virial Theorem in the presence of a radial
distribution of the magnetic field , with
, as the one indicated by observations and numerical simulation.
Our analysis shows that such a description is able to provide, at once, a possible
explanation of three problematic aspects of the cluster structure: i) the flattening of
the entropy profile in the cluster center; ii) the flatness of the
relation;
iii) the increasing steepening of the
relation from the cluster scale towards the
group scales. The available entropy and X-ray luminosity data indicate that an increase of the magnetic field
is required to reproduce at the same time both the
and the
relations.
It follows that a consistent description of the magnetized ICM can provide a simple
explanation of several (or of all) of these still open problems, and thus weakens the
need for the inclusion of other non-gravitational effects which have been proposed so far
for the explanation of some of these features.
This (initial, but not conclusive) analysis can be regarded as a starting point for a more refined analytical exploration of the physics of the magnetized intra-cluster
medium, and it provides testable predictions that can be proven or disproven with the
next coming sensitive observations of groups and clusters in the X-ray band and in the
radio frequency band.
Key words: cosmology: theory / galaxies: clusters: general
© ESO, 2007
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