Issue |
A&A
Volume 521, October 2010
|
|
---|---|---|
Article Number | A78 | |
Number of page(s) | 12 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/201014839 | |
Published online | 22 October 2010 |
The complex structure of Abell 2345: a galaxy cluster with non-symmetric radio relics*
1
Fundación Galileo
Galilei - INAF, Rambla José Ana Fernández Perez 7, 38712
Breña Baja (La Palma), Canary Islands, Spain e-mail: boschin@tng.iac.es
2
Instituto de
Astrofísica de Canarias, C/vía Láctea s/n, 38205 La
Laguna (Tenerife), Canary Islands, Spain
3
Departamento de
Astrofísica, Universidad de La Laguna, Av. del
Astrofísico Francisco Sánchez s/n, 38205 La Laguna
(Tenerife), Canary Islands, Spain
4
Dipartimento di Fisica dell'Università degli Studi
di Trieste, Sezione di Astronomia, via Tiepolo 11, 34143
Trieste, Italy
5
INAF – Osservatorio Astronomico di Trieste,
via Tiepolo 11, 34143 Trieste, Italy
Received:
21
April
2010
Accepted:
4
June
2010
Context. The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still debated.
Aims. We aim to obtain new insights into the internal dynamics of the cluster Abell 2345. This cluster exhibits two non-symmetric radio relics well studied through recent, deep radio data.
Methods. Our analysis is based on redshift data for 125 galaxies acquired at the Telescopio Nazionale Galileo and on new photometric data acquired at the Isaac Newton Telescope. We also use ROSAT/HRI archival X-ray data. We combine galaxy velocities and positions to select 98 cluster galaxies and analyze the internal dynamics of the cluster.
Results. We estimate a mean redshift < z > = 0.1789 and a
line-of-sight (LOS) velocity dispersion ~ 1070 km s-1. The two-dimensional galaxy distribution reveals the presence
of three significant peaks within a region of ~1
Mpc (the E,
NW, and SW peaks). The spectroscopic catalog confirms the presence
of these three clumps. The SW and NW clumps have similar mean
velocities, while the E clump has a larger mean velocity (Δ Vrf ~ 800 km s-1); this structure causes the presence
of the two peaks we find in the cluster velocity distribution. The
difficulty in separating the galaxy clumps leads to a very uncertain
mass estimate M ~ 2 × 1015
. Moreover, the E clump well coincides
with the main mass peak as recovered from the weak gravitational
lensing analysis and is off-set to the east from the BCG by ~1.3´. The ROSAT X-ray data also show a very complex
structure, mainly elongated in the E-W direction, with two (likely
three) peaks in the surface brightness distribution, which, however,
are off-set from the position of the peaks in the galaxy
density. The observed phenomenology agrees with the hypothesis that
we are looking at a complex cluster merger occurring along two
directions: a major merger along the ~E-W direction (having a
component along the LOS) and a minor merger in the western cluster
regions along the ~N-S direction, roughly parallel to the
plane of the sky. The eastern radio relic is elongated in the
direction perpendicular to that of the major merger, while the
peculiar, western radio relic is elongated in the direction
perpendicular to the bisecting of the two merger directions.
Conclusions. Our scenario for the internal dynamics of Abell 2345 strongly supports the use of the “outgoing merger shocks” model to explain the two radio relics, suggesting a consistent justification for their asymmetry.
Key words: galaxies: clusters: individual: Abell 2345 / galaxies: clusters: general / galaxies: distances and redshifts
Table 1 is only available in electronic form at http://www.aanda.org
© ESO, 2010
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