How unusual is the cool-core radio halo cluster CL1821+643?

Kale, Ruta; Parekh, Viral

doi:10.1093/mnras/stw796

Cited by 22 publications

(22 citation statements)

References 40 publications

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“…A two component radio halo is reported in Abell 2142 and is thus unlike typical mini-halos . The systems Abell 2390, Abell 2261 (Sommer & Basu 2014) and CL1821 + 643 (Bonafede et al 2014;Kale & Parekh 2016) are similar to the radio halo reported here. Recently low brightness and steep spectrum emission has been found surrounding the known mini-halos in the clusters PSZ1G139.61+24.20 (Savini et al 2018) and RXJ1720.1+2638 (Savini et al 2019).…”

Section: Mini-halo To Radio Halo Transition Systemsupporting

confidence: 83%

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A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

Kale

Shende

Parekh

2019

Monthly Notices of the Royal Astronomical Society: Letters

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Diffuse radio sources associated with the intra-cluster medium are direct probes of the cosmic ray electrons and magnetic fields. We report the discovery of a diffuse radio source in the galaxy cluster RXCJ0232.2-4420 (SPT-CL J0232-4421, z = 0.2836) using 606 MHz observations with the Giant Metrewave Radio Telescope. The diffuse radio source surrounds the Brightest Cluster Galaxy in the cluster like typical radio mini-halos. However the total extent of it is 550 × 800 kpc 2 , which is larger than minihalos and similar to that of radio halos. The BCG itself is also a radio source with a marginally resolved core at 7 ′′ (30 kpc) resolution. We measure the 606 MHz flux density of the RH to be 52 ± 5 mJy. Assuming a spectral index of 1.3, the 1.4 GHz radio power is 4.5 × 10 24 W Hz −1 . The dynamical state of the cluster has been inferred to be "relaxed" and also as "complex" depending on the classification methods based on the morphology of the X-ray surface brightness. This system thus seems to be in the transition phase from a mini-halo to a radio halo.

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Section: Mini-halo To Radio Halo Transition Systemsupporting

confidence: 83%

“…is the number of beams in the extent of the emission, σ abs is the percentage error on the absolute flux density scale. We used σ abs = 0.1 (e. g. Kale & Parekh 2016) and found N b = 75.6 to get the error of 5 mJy on the 606 MHz flux density of the RH. The K-corrected radio power at frequency ν is…”

Section: Resultsmentioning

confidence: 99%

A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

Kale

Shende

Parekh

2019

Monthly Notices of the Royal Astronomical Society: Letters

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“…Bonafede et al (2014b) discovered a large 1.1 Mpc radio halo in CL1821+643 which contains a strong cool core. If this halo is caused by a merger event, the cluster is in a stage where the merger has not (yet) been able to disrupt the cool core as also noted by Kale and Parekh (2016). For example, because the merger is an off-axis event, or the merger is still in an early stage.…”

Section: Unificationmentioning

confidence: 88%

Diffuse Radio Emission from Galaxy Clusters

et al. 2019

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In a growing number of galaxy clusters diffuse extended radio sources have been found. These sources are not directly associated with individual cluster galaxies. The radio emission reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). We classify diffuse cluster radio sources into radio halos, cluster radio shocks (relics), and revived AGN fossil plasma sources. Radio halo sources can be further divided into giant halos, mini-halos, and possible "intermediate" sources. Halos are generally positioned at cluster center and their brightness approximately follows the distribution of the thermal ICM. Cluster radio shocks (relics) are polarized sources mostly found in the cluster's periphery. They trace merger induced shock waves. Revived fossil plasma sources are characterized by their radio steep-spectra and often irregular morphologies. In this review we give an overview of the properties of diffuse cluster radio sources, with an emphasis on recent observational results. We discuss the resulting implications for the underlying physical acceleration processes that operate in the ICM, the role of relativistic fossil plasma, and the properties of ICM shocks and magnetic fields. We also compile an updated list of diffuse cluster radio sources which will be available on-line (http://galaxyclusters.com).

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“…An example of these outliers is the giant radio halo in the strong cool-core cluster CL 1821+643 (Bonafede et al 2014). A study of the X-ray morphological parameters of this cluster shows that it shares the same properties of galaxy clusters hosting a radio halo, suggesting that it may be a case of a cluster merger in which the cool core has been preserved (Kale & Parekh 2016). More recently, a giant radio halo has been reported in A 2261 and A 2390, neither of which is a major merger (Sommer et al 2016).…”

Section: Introductionmentioning

confidence: 99%

The two-component giant radio halo in the galaxy cluster Abell 2142

Venturi

Rossetti

Brunetti

et al. 2017

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Aims. We report on a spectral study at radio frequencies of the giant radio halo in A 2142 (z=0.0909), which we performed to explore its nature and origin. The optical and X-ray properties of the cluster suggest that A 2142 is not a major merger and the presence of a giant radio halo is somewhat surprising. Methods. We performed deep radio observations of A 2142 with the Giant Metrewave Radio Telescope (GMRT) at 608 MHz, 322 MHz, and 234 MHz and with the Very Large Array (VLA) in the 1-2 GHz band. We obtained high-quality images at all frequencies in a wide range of resolutions, from the galaxy scale, i.e. ∼ 5 , up to ∼ 60 to image the diffuse cluster-scale emission. The radio halo is well detected at all frequencies and extends out to the most distant cold front in A 2142, about 1 Mpc away from the cluster centre. We studied the spectral index in two regions: the central part of the halo, where the X-ray emission peaks and the two brightest dominant galaxies are located; and a second region, known as the ridge (in the direction of the most distant south-eastern cold front), selected to follow the bright part of the halo and X-ray emission. We complemented our deep observations with a preliminary LOw Frequency ARray (LOFAR) image at 118 MHz and with the re-analysis of archival VLA data at 1.4 GHz. Results. The two components of the radio halo show different observational properties. The central brightest part has higher surface brightess and a spectrum whose steepness is similar to those of the known radio halos, i.e. α 1.78 GHz 118 MHz = 1.33 ± 0.08. The ridge, which fades into the larger scale emission, is broader in size and has considerably lower surface brightess and a moderately steeper spectrum, i.e. α 1.78 GHz 118 MHz ∼ 1.5. We propose that the brightest part of the radio halo is powered by the central sloshing in A 2142, in a process similar to what has been suggested for mini-halos, or by secondary electrons generated by hadronic collisions in the ICM. On the other hand, the steeper ridge may probe particle re-acceleration by turbulence generated either by stirring the gas and magnetic fields on a larger scale or by less energetic mechanisms, such as continuous infall of galaxy groups or an off-axis (minor) merger.

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How unusual is the cool-core radio halo cluster CL1821+643?

Cited by 22 publications

References 40 publications

A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

Diffuse Radio Emission from Galaxy Clusters

The two-component giant radio halo in the galaxy cluster Abell 2142

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