J/A+A/656/A154 ClG 0217+70 radio images (Hoang+, 2021)
A 3.5 Mpc long radio relic in the galaxy cluster ClG 0217+70.
Hoang D.N., Zhang X., Stuardi C., Shimwell T.W., Bonafede A., Brueggen M.,
Brunetti G., Botteon A., Cassano R., de Gasperin F., Di Gennaro G.,
Hoeft M., Intema H., Rajpurohit K., Roettgering H.J.A., Simionescu A.,
van Weeren R.J.
<Astron. Astrophys. 656, A154 (2021)>
=2021A&A...656A.154H 2021A&A...656A.154H (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; X-ray sources ; Radio sources
Keywords: galaxies: clusters: individual: ClG 0217+70 -
galaxies: clusters: intracluster medium -
large-scale structure of Universe -
radiation mechanisms: non-thermal - X-rays: galaxies: clusters
Abstract:
Megaparsec-scale radio sources in the form of halos and relics are
often detected in dynamically disturbed galaxy clusters. Although they
are associated with merger-induced turbulence and shocks,
respectively, their formation is not fully understood. Aims. We aim to
identify the mechanisms responsible for particle acceleration and
magnetic field amplification in the halo and relics of the galaxy
cluster ClG 0217+70.
We observed ClG 0217+70 with LOFAR at 141MHz and with VLA at 1.5GHz,
and we combined these observations with VLA 1.4GHz archival data to
study the morphological and spectral properties of the diffuse
sources.We added Chandra archival data to examine the thermal and
non-thermal properties of the halo.
Our LOFAR and VLA data confirm the presence of a giant radio halo in
the cluster centre and multiple relics in the outskirts. The radio and
X-ray emission from the halo are correlated, implying a tight relation
between the thermal and non-thermal components. The diuse radio
structure in the south-east, with a projected size of 3.5Mpc, is the
most extended radio relic detected to date. The spectral index across
the relic width steepens towards the cluster centre, suggesting
electron ageing in the post-shock regions. The shock Mach numbers for
the relics derived from the spectral index map range between 2.0 and
3.2. However, the integrated spectral indices lead to increasingly
high Mach numbers for the relics farther from the cluster centre. This
discrepancy could be because the relation between injection and
integrated spectra does not hold for distant shocks, suggesting that
the cooling time for the radioemitting electrons is longer than the
crossing time of the shocks. The variations in the surface brightness
of the relics and the low Mach numbers imply that the radio-emitting
electrons are re-accelerated from fossil plasma that could originate
in active galactic nuclei.
Description:
LOFAR High Band Antenna (HBA) observations of ClG0217 were performed
for 8 hours on September 26, 2018 (project code: LC10_021).
We observed ClG0217 with the VLA L-band (1.5GHz) in C array on June
3, 2017 (Project: 17A-083) and combine with archival data obtained
with the VLA L-band (1.4GHz) D array between December 4 and 12, 2005
(Project: AD509).
We combined the LOFAR 141MHz data with the VLA 1.4GHz (D-array) and
1.5GHz (C-array) data to make spectral index maps of the radio
sources in the cluster field.
The Chandra observations of ClG0217 using the Advanced CCD Imaging
Spectrometer (ACIS) were performed for 25ks on November 28, 2014
(ObsID: 16293).
Objects:
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RA (2000) DE Designation(s)
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02 17 00.0 +70 36 00 ClG 0217+70 = ClG 0217+70
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 238 21 List of fits images
fits/* . 21 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.date Observation date
52- 62 E11.10 Hz Freq ? Observed frequency
64- 68 I5 Kibyte size Size of FITS file
70-135 A66 --- FileName Name of FITS file, in subdirectory fits
137-238 A102 --- Title Title of the FITS file
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Acknowledgements:
Duy Hoang, hoang(at)hs.uni-hamburg.de
(End) Patricia Vannier [CDS] 10-Dec-2021