ClG 0217+70: A massive merging galaxy cluster with a large radio halo and relics

Zhang, Xiaoyuan; Simionescu, A.; Kaastra, J. S.; Akamatsu, Hiroki; Hoang, D. N.; Stuardi, C.; Weeren, R. J. van; Rudnick, Lawrence; Kraft, Ralph; Brown, Shea

doi:10.1051/0004-6361/202039028

Cited by 9 publications

(28 citation statements)

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“…However, within 640 kpc, the radial profile is roughly constant although there is a hint of spectral flattening. We note that X-ray SB discontinuities are detected at the edges of the northern and southern regions (within 640 kpc) (Zhang et al 2020). Although the nature of the X-ray discontinuities (i.e.…”

Section: Spectral Index Variationsmentioning

confidence: 63%

“…A recent study by Zhang et al (2020) found discontinuities in the X-ray SB towards the N and S edges of the radio halo in the VLA 1.4 GHz data. In addition to the two reported edges, we note that the NE edge of the radio halo in the LOFAR 141 MHz map (Fig.…”

Section: The Ne Edgementioning

confidence: 84%

“…With this low-redshift estimate, pointed out that the power of the radio halo in ClG0217 is an order of magnitude higher than the predicted value from the radio power-X-ray luminosity correlation (Liang et al 2000;Cassano et al 2006;Brunetti et al 2009). However, recent work by Zhang et al (2020) estimated a significantly higher redshift for the cluster, i.e. z = 0.18, from the Fe xxv Heα X-ray emission line that they detected in Chandra archival data.…”

Section: Introductionmentioning

confidence: 84%

“…The galaxy cluster ClG0217+70 (hereafter ClG0217; z = 0.18, Zhang et al 2020) was studied with the Very Large Array (VLA) at 1.4 GHz and 325 MHz by after the first detection with the Westerbork Northern Sky Survey (WENSS; Rengelink et al 1997;Rudnick et al 2006). found that the cluster hosts multiple radio diffuse sources including a radio halo, double relics on opposite sides of the cluster, and internal filaments.…”

Section: Introductionmentioning

confidence: 99%

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A 3.5 Mpc long radio relic in the galaxy cluster ClG 0217+70

Hoang

Zhang

Stuardi

et al. 2021

A&A

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Context. 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. Methods. We observed ClG 0217+70 with LOFAR at 141 MHz and with VLA at 1.5 GHz, and we combined these observations with VLA 1.4 GHz 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. Results. 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 diffuse radio structure in the south-east, with a projected size of 3.5 Mpc, 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 radio-emitting 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.

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Section: Spectral Index Variationsmentioning

confidence: 63%

Section: The Ne Edgementioning

confidence: 84%

Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

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A 3.5 Mpc long radio relic in the galaxy cluster ClG 0217+70

Hoang

Zhang

Stuardi

et al. 2021

A&A

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“…The other two galaxy clusters found to be significant outliers are A1213(Giovannini et al 2009) and CLG 0217+70(Brown et al 2011) Zhang et al (2020). recently demonstrate that by adopting a new revised redshift estimate, the galaxy cluster CLG 0217+70 is not anymore overluminous in radio compared to X-ray, while the case of A1213 is still under investigation.…”

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confidence: 95%

Spectral study of the diffuse synchrotron source in the galaxy cluster Abell 523

Vacca,

Shimwell,

Perley

et al. 2022

Preprint

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The galaxy cluster Abell 523 (A523) hosts an extended diffuse synchrotron source historically classified as a radio halo. Its radio power at 1.4 GHz makes it one of the most significant outliers in the scaling relations between observables derived from multi-wavelength observations of galaxy clusters: it has a morphology that is different and offset from the thermal gas, and it has polarized emission at 1.4 GHz typically difficult to observe for this class of sources. A magnetic field fluctuating on large spatial scales (∼1 Mpc) can explain these peculiarities but the formation mechanism for this source is not yet completely clear. To investigate its formation mechanism, we present new observations obtained with the LOw Frequency ARray at 120-168 MHz and the Jansky Very Large Array at 1-2 GHz, which allow us to study the spectral index distribution of this source. According to our data the source is observed to be more extended at 144 MHz than previously inferred at 1.4 GHz, with a total size of about 1.8 Mpc and a flux density 𝑆 144 MHz = (1.52 ± 0.31) Jy. The spectral index distribution of the source is patchy with an average spectral index 𝛼 ∼ 1.2 between 144 MHz and 1.410 GHz, while an integrated spectral index 𝛼 ∼ 2.1 has been obtained between 1.410 GHz and 1.782 GHz. A previously unseen patch of steep spectrum emission is clearly detected at 144 MHz in the south of the cluster. Overall, our findings suggest that we are observing an overlapping of different structures, powered by the turbulence associated with the primary and a possible secondary merger.

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Using the polarization properties of double radio relics to probe the turbulent compression scenario

Stuardi

Bonafede

Rajpurohit

et al. 2022

A&A

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Context. Radio relics are megaparsec-sized synchrotron sources located in the outskirts of some merging galaxy clusters. Binarymerging systems with a favorable orientation may host two almost symmetric relics, named double radio relics. Aims. Double radio relics are seen preferentially edge-on and, thus, constitute a privileged sample for statistical studies. Their polarization and Faraday rotation properties give direct access to the relics' origin and magnetic fields. Methods. In this paper, we present a polarization and rotation measure (RM) synthesis study of four clusters hosting double radio relics, namely 8C 0212+703, Abell 3365, and PLCK G287.0+32.9; previously missing polarization studies; and ZwCl 2341+0000, for which conflicting results have been reported. We used 1-2 GHz Karl G. Jansky Very Large Array observations. We also provide an updated compilation of known double radio relics with important observed quantities. We studied their polarization and Faraday rotation properties at 1.4 GHz and we searched for correlations between fractional polarization and physical resolution, the distance from the cluster center, and the shock Mach number. Results. The weak correlations found between these quantities are well reproduced by state-of-the-art magneto-hydrodynamical simulations of radio relics, confirming that merger shock waves propagate in a turbulent medium with tangled magnetic fields. Both external and internal Faraday depolarization should play a fundamental role in determining the polarization properties of radio relics at 1.4 GHz. Although the number of double radio relics with RM information is still low, their Faraday rotation properties (i.e., restframe RM and RM dispersion below 40 rad m −2 and non-Gaussian RM distribution) can be explained in the scenario in which shock waves with Mach numbers larger than 2.5 propagate along the plane of the sky and compress the turbulent intra-cluster medium.

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ClG 0217+70: A massive merging galaxy cluster with a large radio halo and relics

Cited by 9 publications

References 50 publications

A 3.5 Mpc long radio relic in the galaxy cluster ClG 0217+70

A 3.5 Mpc long radio relic in the galaxy cluster ClG 0217+70

Spectral study of the diffuse synchrotron source in the galaxy cluster Abell 523

Using the polarization properties of double radio relics to probe the turbulent compression scenario

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