Bibcode
Boschin, W.; Barrena, R.; Girardi, M.
Bibliographical reference
Astronomy and Astrophysics, Volume 521, id.A78
Advertised on:
10
2010
Journal
Citations
19
Refereed citations
18
Description
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 σV ~ 1070 km s-1. The
two-dimensional galaxy distribution reveals the presence of three
significant peaks within a region of ~1 h70-1 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 h70-1
M&sun;. 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.
Table 1 is only available in electronic form at http://www.aanda.org
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