J/A+A/449/461 Radial velocities in A2744 (Boschin+, 2006)
Internal dynamics of the radio-halo cluster A2744.
Boschin W., Girardi M., Spolaor M., Barrena R.
<Astron. Astrophys. 449, 461 (2006)>
=2006A&A...449..461B 2006A&A...449..461B
ADC_Keywords: Clusters, galaxy ; Radial velocities
Keywords: galaxies: clusters: general -
galaxies: clusters: individual: Abell 2744 -
galaxies: distances and redshifts - intergalactic medium -
cosmology: observations
Abstract:
We present a detailed dynamical analysis of the rich galaxy cluster
A2744, containing a powerful diffuse radio-halo. Our analysis is based
on redshift data for 102 galaxies, part of them recovered from
unexplored spectra in the ESO archive. We combine galaxy velocity and
position information to select the cluster members and determine
global dynamical properties of the cluster. We use a variety of
statistical tests to detect possible substructures. We find that A2744
appears as a well isolated peak in the redshift space at =0.306,
which includes 85 galaxies recognized as cluster members. We compute
the line-of-sight (LOS) velocity dispersion of galaxies,
sigmaV=1767-99121km/s, which is significantly larger than what
is expected in the case of a relaxed cluster with an observed X-ray
temperature of 8 keV. We find evidence that this cluster is far from
dynamical equilibrium, as shown by the non Gaussianity of the velocity
distribution, the presence of a velocity gradient and a significant
substructure. Our analysis shows the presence of two galaxy-clumps of
different mean LOS velocities DeltaV∼4000km/s. We detect a main,
low-velocity clump with sigmaV∼1200-1300km/s and a secondary,
high-velocity clump with sigmaV=500-800km/s and located in the S-SW
cluster region. We estimate a cluster mass within 1Mpc of
1.4-2.4M☉, depending on the model adopted to describe the
cluster dynamics. Our results suggest a merging scenario of two clumps
with a mass ratio of 3:1 and a LOS impact velocity of
DeltaVrf∼3000km/s, likely observed just after the core passage. The
merging is occuring roughly in the NS direction with the axis close to
the LOS. This scenario agrees with that proposed on the basis of
recent Chandra results in its general lines although pointing out for
a somewhat more advanced merging phase. Our conclusions support the
view of the connection between extended radio emission and energetic
merging phenomena in galaxy clusters.
Description:
Spectroscopic redshifts for 102 galaxies in the central region of the
galaxy cluster Abell 2744 are presented.
For each galaxy equatorial coordinates and radial velocity are given.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 102 Velocity catalog of 102 spectroscopically
measured galaxies
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Galaxy identification number
4 A1 --- n_Seq [*] *: non-member galaxy
8- 9 I2 h RAh Right ascension J2000 (hours)
11- 12 I2 min RAm Right ascension J2000 (minutes)
14- 18 F5.2 s RAs Right ascension J2000 (seconds)
21 A1 --- DE- Declination J2000 (sign)
22- 23 I2 deg DEd Declination J2000 (degrees)
25- 26 I2 arcmin DEm Declination J2000 (minutes)
28- 31 F4.1 arcsec DEs Declination J2000 (seconds)
33- 38 I6 km/s HRVN ?=- Heliocentric radial velocity from NTT data
40- 42 I3 km/s e_HRVN ?=- 1-sigma error on the HRVN
44- 49 I6 km/s HRV Heliocentric radial velocity
52- 54 I3 km/s e_HRV 1-sigma error on the HRV
56- 58 I3 --- CN ?=- Couch & Newell (1984ApJS...56..143C 1984ApJS...56..143C)
identification number, CN A2744 NNN in Simbad
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Acknowledgements: Walter Boschin, boschin(at)tng.iac.es
(End) Walter Boschin [Fundacion Galileo Galilei], P. Vannier [CDS] 22-Nov-2005