Detalles de publicación
PP 08014
Optical analysis of the poor clusters Abell 610, Abell 725, and Abell 796, containing diffuse radio sources
(1) Fundaci´on Galileo Galilei – INAF, Spain
(2) Dipartimento di Astronomia, Universit`a degli Studi di Trieste, Italy
(3) Instituto de Astrofisica de Canarias
(4) INAF – Osservatorio Astronomico di Trieste, Italy
(5) Centre for Astrophysics & Supercomputing, Swinburne University, Australia
Aims. We study the dynamical status of the poor, low X–ray luminous galaxy
clusters Abell 610, Abell 725, and Abell 796 (at z = 0.1, 0.09, and 0.16,
respectively), containing diffuse radio sources (relic, relic, and possible
halo, respectively).
Methods. Our analysis is based on new spectroscopic data obtained at the
William Herschel Telescope for 158 galaxies, new photometry obtained at the
Isaac Newton Telescope with the addition of data recovered from the Data
Release 5 of the Sloan Digital Sky Survey. We use statistical tools to select
57, 36, and 26 cluster members and to analyze the kinematics of cluster
galaxies, as well as to study the 2D cluster structure.
Results. The low values we compute for the global line–of–sight velocity
dispersion of galaxies (sigma_v = 420 − 700 km/s) confirm that these clusters
are low–mass clusters. Abell 610 shows a lot of evidence of substructure. It
seems to be formed by two structures separated by ∼ 700 km/s in the cluster
rest–frame, having comparable sigma_v ∼ 200 km/s and likely causing a velocity
gradient. The velocity of the brightest cluster member (BCMI; a bright radio
source) is very close to the mean velocity of the higher velocity structure. A
third small, low–velocity group hosts the second brightest cluster member
(BCMII). The analysis of the 2D galaxy distribution shows a bimodal distribution
in the core elongated in the SE–NWdirection and likely associated to BCMI and
BCMII groups. Abell 725 and Abell 796, which are less sampled, show marginal
evidence of substructure in the velocity space. They are elongated in the 2D
galaxy distribution. For both Abell 610 and Abell 725 we shortly discuss the
possible connection with the hosted diffuse radio relic.
Conclusions. Our results show that relic radio sources are likely connected with
merger events, but are not limited to massive clusters. About the possible halo
source in Abell 796, there is some evidence of a merger event in this
non–massive cluster, but a pointed radio observation is necessary to confirm
this halo.
clusters Abell 610, Abell 725, and Abell 796 (at z = 0.1, 0.09, and 0.16,
respectively), containing diffuse radio sources (relic, relic, and possible
halo, respectively).
Methods. Our analysis is based on new spectroscopic data obtained at the
William Herschel Telescope for 158 galaxies, new photometry obtained at the
Isaac Newton Telescope with the addition of data recovered from the Data
Release 5 of the Sloan Digital Sky Survey. We use statistical tools to select
57, 36, and 26 cluster members and to analyze the kinematics of cluster
galaxies, as well as to study the 2D cluster structure.
Results. The low values we compute for the global line–of–sight velocity
dispersion of galaxies (sigma_v = 420 − 700 km/s) confirm that these clusters
are low–mass clusters. Abell 610 shows a lot of evidence of substructure. It
seems to be formed by two structures separated by ∼ 700 km/s in the cluster
rest–frame, having comparable sigma_v ∼ 200 km/s and likely causing a velocity
gradient. The velocity of the brightest cluster member (BCMI; a bright radio
source) is very close to the mean velocity of the higher velocity structure. A
third small, low–velocity group hosts the second brightest cluster member
(BCMII). The analysis of the 2D galaxy distribution shows a bimodal distribution
in the core elongated in the SE–NWdirection and likely associated to BCMI and
BCMII groups. Abell 725 and Abell 796, which are less sampled, show marginal
evidence of substructure in the velocity space. They are elongated in the 2D
galaxy distribution. For both Abell 610 and Abell 725 we shortly discuss the
possible connection with the hosted diffuse radio relic.
Conclusions. Our results show that relic radio sources are likely connected with
merger events, but are not limited to massive clusters. About the possible halo
source in Abell 796, there is some evidence of a merger event in this
non–massive cluster, but a pointed radio observation is necessary to confirm
this halo.