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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file list.dat 133 3 List of fits images fits/* . 3 Individual fits images -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Acknowledgements: Andrea Botteon, botteon(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 26-Aug-2019
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