J/A+A/658/A159 126 member galaxies of A780 radial velocities (Girardi+, 2022)
Accretion processes in the galaxy cluster Hydra A/Abell 780.
Girardi M., Boschin W., Nonino M., Innocentin C., De Grandi S.
<Astron. Astrophys. 658, A159 (2022)>
=2022A&A...658A.159G 2022A&A...658A.159G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Redshifts ; Spectroscopy ; Radial velocities ;
Optical
Keywords: galaxies: clusters: individual: Abell 780 -
galaxies: clusters: general - galaxies: kinematics and dynamics -
galaxies: clusters: individual: Hydra A
Abstract:
Clusters of galaxies evolve and accrete mass, mostly from small galaxy
systems. Our aim is to study the velocity field of the galaxy cluster
Abell 780, which is known for the powerful radio source Hydra A at its
center and where a spectacular X-ray tail associated with the galaxy
LEDA 87445 has been discovered. Our analysis is based on the new
spectroscopic data for hundreds of galaxies obtained with the Italian
Telescopio Nazionale Galileo and the Very Large Telescope. We have
constructed a redshift catalog of 623 galaxies and selected a sample
of 126 cluster members. We analyze the internal structure of the
cluster using a number of techniques. We estimate the mean redshift
z=0.0545, the line-of-sight velocity dispersion σv∼800km/s,
and the dynamical mass M200∼5.4x1014M☉. The global properties
of Abell 780 are typical of relaxed clusters. On a smaller scale, we
can detect the presence of a galaxy group associated with LEDA 87445
in projected phase space. The mean velocity and position of the center
of the group agree well with the velocity and position of LEDA 87445.
We estimate the following parameters of the collision. The group is
characterized by a higher velocity relative to the main system. It is
infalling at a rest frame velocity of Vrf~+870km/s and lies at a
projected distance D∼1.1Mpc to the south, slightly southeast of the
cluster center. The mass ratio between the group and the cluster is
∼1:5. We also find evidence of an asymmetry in the velocity
distribution of galaxies in the inner cluster region, which might be
related to a small low-velocity group detected as a substructure at
Vrf~-750km/s. We conclude that A780, although dynamically relaxed at
first sight, contains small substructures that may have some impact on
the energetics of the core region.
Description:
The table contains radial velocities of 126 member galaxies of the
galaxy cluster A780. Multi-object spectroscopic observations in the
field of A780 were carried out at the the Italian Telescopio Nazionale
Galileo (TNG) in June 2016 and at the Very Large Telescope
(VLT-ESO) in January, February, and March 2017. At TNG we used the
instrument Device Optimized for the Low Resolution (DOLORES) in
multi-object spectroscopy (MOS) mode with the LR-B Grism. In total, we
observed five MOS masks for a total of 194 slits. The total exposure
time was 3600s for each of the five masks. At VLT we used the
instrument VIMOS in MOS mode with the LR-blue grism. In total, we
observed three MOS mask pointing for a total of 1407 slits. The total
exposure time was six hours, distributed over three pointings. We
combined new velocities with those from literature (Smith et al.
2004AJ....128.1558S 2004AJ....128.1558S, Cat. J/AJ/128/1558).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 53 126 Radial velocities of 126 member galaxies of A780
--------------------------------------------------------------------------------
See also:
J/AJ/128/1558 : NOAO Fundamental Plane Survey (Smith+, 2004)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/126] Sequential number (1)
7- 8 I2 h RAh Right ascension (J2000.0)
10- 11 I2 min RAm Right ascension (J2000.0)
13- 17 F5.2 s RAs Right ascension (J2000.0)
20 A1 --- DE- Declination sign (J2000.0)
21- 22 I2 deg DEd Declination (J2000.0)
24- 25 I2 arcmin DEm Declination (J2000.0)
27- 30 F4.1 arcsec DEs Declination (J2000.0)
33- 37 F5.2 mag rmag [13.13,22.33] CFHT r magnitudes
39- 44 I6 km/s HRV [14401,18745] Heliocentric radial velocity
47- 49 I3 km/s e_HRV [28,272] Uncertainty on HRV
51- 53 A3 --- r_HRV [VTL] Origin of HRV (2)
--------------------------------------------------------------------------------
Note (1): IDs. 47 and 97 are the BCG and LEDA 87445, respectively.
Note (2): Origin of HRV as follows:
V = VLT
T = TNG
L = Literature - Smith et al. (2004AJ....128.1558S 2004AJ....128.1558S, Cat. J/AJ/128/1558)
--------------------------------------------------------------------------------
Acknowledgements:
Marisa Girardi, marisa.girardi(at)inaf.it
(End) Patricia Vannier [CDS] 15-Dec-2021