J/A+A/630/A77 Lyra system LoFAR and XMM images (Botteon+, 2019)
Particle acceleration in a nearby galaxy cluster pair:
the role of cluster dynamics.
Botteon A., Cassano R., Eckert D., Brunetti G., Dallacasa D., Shimwell T.W.,
van Weeren R.J., Gastaldello F., Bonafede A., Brueggen M., Birzan L.,
Clavico S., Cuciti V., de Gasperin F., De Grandi S., Ettori S.,
Ghizzardi S., Rossetti M., Roettgering H.J.A., Sereno M.
<Astron. Astrophys. 630, A77 (2019)>
=2019A&A...630A..77B 2019A&A...630A..77B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Radio sources ; X-ray sources
Keywords: radiation mechanisms: non-thermal - radiation mechanisms: thermal -
galaxies: clusters: intracluster medium -
galaxies: clusters: individual: RXC J1825.3+3026 -
galaxies: clusters: individual: CIZA J1824.1+3029 -
galaxies: clusters: general
Abstract:
Diffuse radio emission associated with the intra-cluster medium (ICM)
is observed in a number of merging galaxy clusters. It is currently
believed that in mergers a fraction of the kinetic energy is channeled
into non-thermal components, such as turbulence, cosmic rays and
magnetic fields, that may lead to the formation of giant synchrotron
sources in the ICM.
Studying merging galaxy clusters in different evolutionary phases is
fundamental to understanding the origin of radio emission in the ICM.
We observed the nearby galaxy cluster pair RXC J1825.3+3026 (z∼0.065)
and CIZA J1824.1+3029 (z∼0.071) at 120-168MHz with the LOw Frequency
ARray (LOFAR) and made use of a deep (240 ks) XMM-Newton dataset to
study the nonthermal and thermal properties of the system. RXC
J1825.3+3026 is in a complex dynamical state, with a primary on-going
merger in the E-W direction and a secondary later stage merger with a
group of galaxies in the SW, while CIZA J1824.1+3029 is dynamically
relaxed. These two clusters are in a pre-merger phase.
We report the discovery of a Mpc-scale radio halo with a low surface
brightness extension in RXC J1825.3+3026 that follows the X-ray
emission from the cluster center to the remnant of a galaxy group in
the SW. This is among the least massive systems and the faintest giant
radio halo known to date. Contrary to this, no diffuse radio emission
is observed in CIZA J1824.1+3029 nor in the region between the
pre-merger cluster pair. The power spectra of the X-ray surface
brightness fluctuations of RXC J1825.3+3026 and CIZA J1824.1+3029 are
in agreement with the findings for clusters exhibiting a radio halo
and the ones where no radio emission has been detected, respectively.
We provide quantitative support to the idea that cluster mergers play
a crucial role in the generation of non-thermal components in the ICM.
Description:
The cluster pair RXCJ1825/CIZAJ1824 was observed with LOFAR in
HBADUALINNER mode on 21 June 2018 (project code: LC10_013). The
observation was performed following the scheme of the LOFAR Two-meter
Sky Survey (LoTSS; Shimwell et al., 2017, Cat. J/A+A/598/A104), i.e.
8 hr on-source time bookended by two 10 min scans of the flux
calibrator 3C295 using LOFAR HBA operating in the 120-168MHz
frequency band. The 48MHz bandwidth is centered at the central
frequency 144MHz, which is also the reference frequency for the LOFAR
images shown here.
RXCJ1825 was observed in the context of the XMM-Newton Cluster
Outskirts Project (X-COP) for a total exposure time of 240ks divided
into two central pointings and four offset pointings, one of whose
containing CIZAJ1824. We show the XMM-Newton background-subtracted and
exposure-corrected mosaic image in the 0.5-2.0keV band of the cluster
pair.
Objects:
--------------------------------------------
RA (2000) DE Designation(s)
--------------------------------------------
18 25 20.0 +30 26 11.2 RXC J1825.3+3026
18 24 06.8 +30 29 32.5 CIZA J1824.1+3029
--------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 133 3 List of fits images
fits/* . 3 Individual fits images
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See also:
J/A+A/598/A104 : LOFAR Two-metre Sky Survey (Shimwell+, 2017)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
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- 51 A22 "datime" Obs.date Observation date
53- 59 F7.3 MHz Freq ? Observed frequency
61- 65 I5 Kibyte size Size of FITS file
67- 90 A24 --- FileName Name of FITS file, in subdirectory fits
92-133 A42 --- Title Title of the FITS file
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Acknowledgements:
Andrea Botteon, botteon(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 26-Aug-2019