Detalles de publicación
PP 07015
The dynamical status of the galaxy cluster Abell 115
(1) IAC, (2) TNG, Fundacion Galileo Galilei - INAF, (3) Dipartimento
di Astronomia of the Universita degli Studi di Trieste (Italy),
(4) INAF - Osservatorio Astronomico di Trieste (Italy),
(5) Centre for Astrophysics \& Supercomputing, Swinburne University (Australia)
We present the results of a new spectroscopic and photometric survey of the
hot, binary X--ray cluster A115 at z=0.193, containing a radio relic.
Our analysis is based on new spectroscopic data obtained at the Telescopio
Nazionale Galileo for 115 galaxies and on new photometric data obtained at
the Isaac Newton Telescope in a large field. We combine galaxy velocity and
position information to select 85 galaxies recognized as cluster members,
determine global dynamical properties and detect substructures. We find that
A115 appears as a well isolated peak in the redshift space, with a global
line--of--sight (LOS) velocity dispersion sigma_v=1362_{-108}^{+126}$ km/s.
Our analysis confirms the presence of two structures of cluster--type well
recognizable in the plane of the sky and shows that they differ of ~2000 km/s
in the LOS velocity. The northern, high velocity subcluster (A115N) is
likely centred on the second brightest cluster galaxy (BCM--A, coincident with
radio source 3C28) and the northern X--ray peak. The southern, low velocity
subcluster (A115S) is likely centred on the first brightest cluster galaxy
(BCM--B) and the southern X--ray peak. We estimate that A115S is slightly
dynamically more important than A115N having sigma_v=900-1100 km/s vs. sigma_v=750-850 km/s. Moreover, we find evidence for two small groups at
low velocities. Our results agree with a pre--merging scenario where A115N
and A115S are colliding with a LOS impact velocity (Delta v_rf) ~ 1600 km/s.
The most likely solution to the two--body problem suggests that the merging
axis lies at ~20 deg from the plane of the sky and that the cores will cross after ~0.1 Gyr. The radio relic with its largest dimension perpendicular to
the merging axis is likely connected to this merger.
hot, binary X--ray cluster A115 at z=0.193, containing a radio relic.
Our analysis is based on new spectroscopic data obtained at the Telescopio
Nazionale Galileo for 115 galaxies and on new photometric data obtained at
the Isaac Newton Telescope in a large field. We combine galaxy velocity and
position information to select 85 galaxies recognized as cluster members,
determine global dynamical properties and detect substructures. We find that
A115 appears as a well isolated peak in the redshift space, with a global
line--of--sight (LOS) velocity dispersion sigma_v=1362_{-108}^{+126}$ km/s.
Our analysis confirms the presence of two structures of cluster--type well
recognizable in the plane of the sky and shows that they differ of ~2000 km/s
in the LOS velocity. The northern, high velocity subcluster (A115N) is
likely centred on the second brightest cluster galaxy (BCM--A, coincident with
radio source 3C28) and the northern X--ray peak. The southern, low velocity
subcluster (A115S) is likely centred on the first brightest cluster galaxy
(BCM--B) and the southern X--ray peak. We estimate that A115S is slightly
dynamically more important than A115N having sigma_v=900-1100 km/s vs. sigma_v=750-850 km/s. Moreover, we find evidence for two small groups at
low velocities. Our results agree with a pre--merging scenario where A115N
and A115S are colliding with a LOS impact velocity (Delta v_rf) ~ 1600 km/s.
The most likely solution to the two--body problem suggests that the merging
axis lies at ~20 deg from the plane of the sky and that the cores will cross after ~0.1 Gyr. The radio relic with its largest dimension perpendicular to
the merging axis is likely connected to this merger.