J/A+A/672/A28 943MHz EMU image of the galaxy cluster A3718 (Loi+, 2023)
A 600 kpc complex radio source at the center of Abell 3718 discovered by the
EMU and POSSUM surveys.
Loi F., Brienza M., Riseley C.J., Rudnick L., Boschin W., Lovisari L.,
Carretti E., Koribalski B., Stuardi C., O'Sullivan S.P., Bonafede A.,
Filipovic M.D., Hopkins A.
<Astron. Astrophys. 672, A28 (2023)>
=2023A&A...672A..28L 2023A&A...672A..28L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Radio sources
Keywords: galaxies: clusters: individual: Abell 3718 -
galaxies: clusters: intracluster medium - surveys
Abstract:
Multifrequency studies of galaxy clusters are crucial for inferring
their dynamical states and physics. Moreover, these studies allow us
to investigate cluster-embedded sources, whose evolution is affected
by the physical and dynamical condition of the cluster itself. So far,
these kinds of studies have been preferentially conducted on clusters
visible from the northern hemisphere due to the high-fidelity imaging
capabilities of ground-based radio interferometers located there.
In this paper, we conducted a multifrequency study of the poorly known
galaxy cluster Abell 3718. We investigated the unknown origin of an
extended radio source with a length of ∼612kpc at 943MHz detected
in images from the Evolutionary Map of the Universe (EMU) and
POlarisation Sky Survey of the Universe's Magnetism (POSSUM)
surveys.
We analyzed optical and X-ray data to infer the dynamical state of the
cluster and, in particular, the merger activity. We conducted a radio
spectral index study from 943MHz up to 9GHz. We also evaluated the
polarization properties of the brightest cluster-embedded sources to
understand if they are related to the radio emission observed on
larger scales. The cluster appears to be in a relaxed dynamical state,
but there is clear asymmetry of the X-ray surface brightness
distribution perpendicular to the direction of the largest angular
extension of the radio source. The morphology of the cluster radio
emission observed from 900MHz to 9GHz shows a system composed of a
northern compact radio source and a southern radio galaxy whose jets
are bent in the direction of an ultra-steep (alpha~=3.6), thin (few
tens of kpc) arc of radio emission between the first two radio
sources. The spectral index gradient along the radio source and the
polarization images at high frequency suggest that the thin arc is an
extension of the southern radio galaxy, which may have been energized
by interacting with the X-ray gas. An additional structure extending
to the northwest from the southern radio galaxy may be an unusual
truncated radio jet that either failed to expand or faded away due to
energy losses. Deeper X-ray and radio observations are needed to
better constrain the physics at play in this cluster.
Description:
The EMU observations used in this work have the following ASKAP
Scheduling Block IDs (SBIDs): SBID 9351.
The EMU data cover the frequency range between 800MHz and 1088MHz
Multiwavelength image of galaxy cluster A3718.
Objects:
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RA (2000) DE Designation(s)
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20 55 54.99 -54 55 29.9 A3718 = ACO 3718
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 107 1 Information on fits image
fits/* . 1 fits image
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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- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 48 A21 "datime" Obs.date Observation date
50- 53 I4 Kibyte size Size of FITS file
55- 62 A8 --- FileName Name of FITS file, in subdirectory fits
64-107 A44 --- Title Title of the FITS file
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Acknowledgements:
Francesca Loi, francesca.loi(at)inaf.it
(End) Patricia Vannier [CDS] 16-Mar-2023