Bibcode
Girardi, M.; Boschin, W.; Barrena, R.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 517, id.A65
Fecha de publicación:
7
2010
Revista
Número de citas
14
Número de citas referidas
13
Descripción
Context. The mechanisms giving rise to diffuse radio emission in galaxy
clusters, and in particular their connection with cluster mergers, are
still debated. Aims: We seek to explore the internal dynamics of
the cluster Abell 2294, which has been shown to host a radio halo. Methods: Our analysis is mainly based on redshift data for 88
galaxies acquired at the Telescopio Nazionale Galileo. We combine galaxy
velocities and positions to select 78 cluster galaxies and analyze its
internal dynamics. We also use both photometric data acquired at the
Isaac Newton Telescope and X-ray data from the Chandra archive.
Results: We re-estimate the redshift of the large, brightest cluster
galaxy (BCG) obtaining < z > = 0.1690, which closely agrees with
the mean cluster redshift. We estimate a quite large line-of-sight (LOS)
velocity dispersion σ_V ~ 1400 km s-1 and X-ray
temperature TX ~ 10 keV. Our optical and X-ray analyses
detect substructure. Our results imply that the cluster is composed of
two massive subclusters separated by a LOS rest frame velocity
difference Vrf ~ 2000 km s-1, very closely
projected in the plane of sky along the SE-NW direction. This
observational picture, interpreted in terms of the analytical two-body
model, suggests that Abell 2294 is a cluster merger elongated mainly in
the LOS direction and captured during the bound outgoing phase, a few
fractions of Gyr after the core crossing. We find that Abell 2294 is a
very massive cluster with a range of M = 2-4 × 1015
h70-1 M&sun;, depending on the adopted
model. In contrast to previous findings, we find no evidence of Hα
emission in the spectrum of the BCG galaxy. Conclusions: The
emerging picture of Abell 2294 is that of a massive, quite
“normal” merging cluster, like many clusters hosting diffuse
radio sources. However, perhaps because of its particular geometry, more
data are needed for reach a definitive, more quantitative conclusion.
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