J/A+A/691/A99 A2061-A2067 LOFAR images (Pignataro+, 2024)
Mind the Gap between A2061 and A2067:
Unveiling new diffuse, large-scale radio emission.
Pignataro G.V., Bonafede A., Bernardi G., Balboni M., Vazza F.,
van Weeren R.J., Ubertosi F., Cassano R., Brunetti G., Botteon A.,
Venturi T., Akamatsu H., Drabent A., Hoeft M.
<Astron. Astrophys. 691, A99 (2024)>
=2024A&A...691A..99P 2024A&A...691A..99P (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Radio sources
Keywords: galaxies: clusters: general - large-scale structure of Universe
Abstract:
The clusters Abell 2061 and Abell 2067 in the Corona Borealis
supercluster have been studied at different radio frequencies and are
both known to host diffuse radio emission. The aim of this work is to
investigate the radio emission in between them, suggested by low
resolution observations. We analyse deep LOFAR HBA observations at
144MHz to follow up on the possible intercluster filament suggested by
previous 1.4GHz observations. We investigate the radial profiles and
the point-to-point surface brightness correlation of the emission in
A2061 with radio and Xray observations, to describe the nature of the
diffuse emission. We report the detection of diffuse radio emission on
800 kpc scale, more extended than previously known, reaching beyond
the radio halo in A2061 towards A2067 and over the separation outside
the two clusters R500 radii. We confirm the presence of a radio halo
in A2061, while do not find evidence of diffuse emission in A2067. The
surface brightness profile from the centre of A2061 shows an excess of
emission with respect to the azimuthally averaged radio halo profile
and X-ray background. We explore three different dynamical scenario to
explain the nature of the diffuse emission. We analyse a trail of
emission of 760kpc between the radio halo and radio relic in A2061.
This pre merger system closely resembles the two other cluster pairs
where radio bridges connecting the radio halos on Mpc scales have been
detected. The diffuse emission extends beyond each cluster R500 radius
but in this unique case, the absence of the radio halo in A2067 is
likely the reason for the observed gap between the two systems.
However, the point-to-point correlation results are challenging to
explain. The classification of the emission remains unclear, and
detailed spectral analysis and further Xray observations are required
to understand the origin of the diffuse emission.
Description:
The two clusters were observed as part of a pointing on the
northern part of CSC, therefore the system is distant ∼35' from the
pointing center. We observed the CSC with LOFAR HBA using the same
setup as LoTSS, that is in the frequency range 120-168MHz, divided
into 244 sub-bands of 64 channels each. The total observing time for
CSC North was 32 hours (proposal code: LC014_18, P.I: Vazza), however
only 16 hours are not affected by severe ionospheric conditions and
used for this analysis. This observation was carried out in
co-observing mode with the LoTSS and the data reduction follows the
LoTSS reduction scheme
Low and high-resolution images of A2061-A2067,
Objects:
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RA (2000) DE Designation(s)
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15 21 19.89 +30 37 13.0 A2061 = ACO 2061
15 23 13.99 +30 54 23.9 A2067 = ACO 2067
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 157 2 List of fits images
fits/* . 2 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- 56 I5 Kibyte size Size of FITS file
58-106 A49 --- FileName Name of FITS file, in subdirectory fits
108-157 A50 --- Title Title of the FITS file
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Acknowledgements:
Giada Pignataro, giada.pignataro2(at)unibo.it
(End) Patricia Vannier [CDS] 26-Sep-2024