Issue |
A&A
Volume 397, Number 1, January I 2003
|
|
---|---|---|
Page(s) | 53 - 61 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20021474 | |
Published online | 11 December 2002 |
The diffuse radio emission from the Coma cluster at 2.675 GHz and 4.85 GHz
1
Max–Planck–Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2
SMTO, Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, Arizona 85721, USA
3
Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
Corresponding author: M. Thierbach, thierb@mpifr-bonn.mpg.de
Received:
5
October
2001
Accepted:
7
October
2002
We present new measurements of the diffuse radio halo emission from the Coma cluster of galaxies at 2.675 GHz and 4.85 GHz using the Effelsberg 100–m telescope. After correction for the contribution from point sources we derive the integrated flux densities for the halo source (Coma C), and
. These values verify the strong steepening of the radio spectrum of Coma C at high frequencies. Its extent strongly depends on frequency, at 4.85 GHz it is only marginally visible. The measurement at 4.85 GHz is the first flux density determination for Coma C at this high frequency. In order to quantify the spectral steepening we compare the expectations for the spectrum of Coma C with the observations, resorting to basic models for radio halo formation. The in–situ acceleration model provides the best fit to the data. From equipartition assumptions we estimate a magnetic field strength
in the intracluster medium of Coma, where k is the energy ratio of the positively and negatively charged particles.
As a by–product of the 2.675 GHz observation we present a new flux density for the diffuse emission of the extended source 1253+275 (
). This measurement provides a smaller error range for the power–law fit to the spectrum (
) compared to previous investigations and yields an equipartition magnetic field strength of
.
Key words: galaxies: clusters: individual: Coma cluster, 1253+275 / galaxies: intergalactic medium
© ESO, 2003
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.