J/MNRAS/480/1187 Multi-object spectroscopy of CL1821+643 (Boschin+, 2018)
Multi-object spectroscopy of CL1821+643: a dynamically relaxed cluster with a
giant radio halo?
Boschin W., Girardi M.
<Mon. Not. R. Astron. Soc., 480, 1187-1196 (2018)>
=2018MNRAS.480.1187B 2018MNRAS.480.1187B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, spectra
Keywords: galaxies: clusters: general -
galaxies: clusters: individual: CL1821+643 -
galaxies: kinematics and dynamics
Abstract:
We present the study of the dynamical status of the galaxy cluster
CL1821+643, a rare and intriguing cool-core cluster hosting a giant
radio halo. We base our analysis on new spectroscopic data for 129
galaxies acquired at the Italian Telescopio Nazionale Galileo. We also
use spectroscopic data available from the literature and photometric
data from the Sloan Digital Sky Survey. We select 120 cluster member
galaxies and compute the cluster redshift ∼0.296 and the
global line-of-sight velocity dispersion σV∼1100km/s. The
results of our analysis are consistent with CL1821+643 being a massive
(M>1015M_☉) dynamically relaxed cluster dominated by a big and
luminous elliptical at the centre of the cluster potential well. None
of the tests employed to study the cluster galaxies kinematics in the
1D (velocity information), 2D (spatial information), and 3D (combined
velocity and spatial information) domains is able to detect
significant substructures. While this picture is in agreement with
previous results based on X-ray data and on the existence of the
central cool core, we do not find any evidence of a merging process
responsible for the radio halo discovered in this cluster. Thus, this
radio halo remains an open problem that raises doubts about our
understanding of diffuse radio sources in clusters.
Description:
We used the instrument DOLORES of the TNG to perform multi-object
spectroscopic (MOS) observations of CL1821 in 2016 June (program
CAT16A_15). In particular, we observed four MOS masks with the LR-B
Grism2 obtaining spectra for 155 objects. The total exposure times
were 5400s for three masks and 3600s for the last one. We also
explored the NASA/IPAC Extragalactic Database (NED)4 to search for
galaxies with known redshift lying in the field covered by our
spectroscopic survey. In total, we found a set of 72 galaxies with
measured redshift. 14 of these galaxies are in common with our TNG
data. Since there is no evidence of systematic deviations between
these 14 literature redshifts and our measurements, we added the
remaining 58 NED galaxies to our sample. Our final spectroscopic
catalogue includes 187 galaxies in the field of CL1821. For all the
galaxies, we also use photometric information from the Sloan Digital
Sky Survey (SDSS) DR13 in the magnitude bands r' and i'. About the
analysis of the 2D spatial distribution of the spectroscopic member
galaxies, we employed the 2D adaptive-kernel method of Pisani et al.
(1996MNRAS.278..697P 1996MNRAS.278..697P, hereafter 2D-DEDICA). This test detects CL1821
as a very prominent galaxy peak with two low-density secondary clumps:
the densest one is located ∼2arcmin N of the cluster centre (density
only ∼35 per cent the main peak) and the second one lies ∼4 arcmin ESE
of the cluster centre.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 48 187 Radial velocities of 187 galaxies in the field
of CL1821
table2.dat 38 3 The 2D structure of CL1821. Results from the
spectroscopic sample according to the
2D-DEDICA method
table3.dat 38 2 The 2D structure of CL1821. Results from the
sample of photometric likely members according
to the 2D-DEDICA method
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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 --- ID Identification number of each galaxy (1)
5 A1 --- f_ID Flag on ID (2)
7- 8 I2 h RAh Right Ascension (J2000)
10- 11 I2 min RAm Right Ascension (J2000)
13- 17 F5.2 s RAs Right Ascension (J2000)
19 A1 --- DE- Declination sign (J2000)
20- 21 I2 deg DEd Declination (J2000)
23- 24 I2 arcmin DEm Declination (J2000)
26- 29 F4.1 arcsec DEs Declination (J2000)
31- 35 F5.2 --- rmag r-band magnitude from the Sloan Digital Sky
Survey (SDSS) DR13
37 A1 --- f_HRV Flag on HRV (3)
39- 44 I6 km/s HRV Heliocentric radial velocities
46- 48 I3 km/s e_HRV HRV error
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Note (1): Galaxy ID 94 is quasar H1821+643
Note (2): Flag as follows:
* = This is a non-member galaxy
Note (3): Flag as follows:
* = This velocities are taken from the literature
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Byte-by-byte Description of file: table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Subclump Subclumps of CL1821 (1)
5- 7 I3 --- Ns Number of assigned member galaxies
9- 10 I2 h RAh Right Ascension (J2000)
12- 13 I2 min RAm Right Ascension (J2000)
15- 18 F4.1 s RAs Right Ascension (J2000)
20 A1 --- DE- Declination sign (J2000)
21- 22 I2 deg DEd Declination (J2000)
24- 25 I2 arcmin DEm Declination (J2000)
27- 28 I2 arcsec DEs Declination (J2000)
30- 33 F4.2 --- rhoS Relative density with respect to the highest
peak
35- 38 F4.1 --- chi2S Reduced chi-square of the peak
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Note (1): C for center (prominent galaxy peak), N for North,
NNE for north-northeast and ESE for east-southeast.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 16-May-2022