New mysteries and challenges from the Toothbrush relic: wideband observations from 550 MHz to 8 GHz

Rajpurohit, K.; Hoeft, M.; Vazza, Franco; Rudnick, Lawrence; Weeren, R. J. van; Wittor, Denis; Drabent, A.; Brienza, M.; Bonnassieux, E.; Locatelli, Nicola; Kale, Ruta; Dumba, C.

doi:10.1051/0004-6361/201937139

Cited by 71 publications

(147 citation statements)

References 90 publications

(172 reference statements)

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“…The integrated spectral index of the relic between 58 MHz and 18.6 GHz is −1.16 ± 0.03. The spectral index value is consistent with our previous estimates (Rajpurohit et al 2018(Rajpurohit et al , 2020. Recently, the power-law spectrum results are also found for the relic in CIZA J2242.8+5301 (Loi et al 2020).…”

Section: Integrated Spectrumsupporting

confidence: 92%

“…At face value, this implies that the shock strength remains the same over an ∼1.8 Mpc scale. As argued in (Rajpurohit et al 2020), the shock surface indeed shows a distribution of Mach numbers, thus a single Mach number derived above can only roughly characterize the shock. Most importantly, the tail of the Mach number distribution toward high values determine the radio spectral index (Wittor et al 2019;Rajpurohit et al 2020).…”

Section: Integrated Spectrummentioning

confidence: 91%

“…To obtain the integrated spectrum of the relic, we combined our new flux density measurements with those presented in Rajpurohit et al (2020). In addition, we included the flux density measurements from the LOFAR LBA observations at 58 MHz (de Gasperin et al 2020).…”

Section: Integrated Spectrummentioning

confidence: 99%

“…They suggest that SZ contamination leads to a high frequency steepening for relics, albeit not at the level claimed by Stroe et al (2016). Recently, we studied the integrated spectrum of the relic between 120 MHz and 8 GHz and excluded any steepening up to 8 GHz (Rajpurohit et al 2020). However, the spectral behavior of the relic remained uncertain between 10 and 20 GHz.…”

Section: Introductionmentioning

confidence: 97%

“…The merging galaxy cluster 1RXS J0603.3+4213, located at a redshift of z = 0.225, is one of the most intriguing clusters hosting a spectacular toothbrush-shaped relic (van Weeren et al 2012(van Weeren et al , 2016Rajpurohit et al 2018Rajpurohit et al , 2020de Gasperin et al 2020). It consists of three distinct components, namely the brush (B1) and two parts forming the handle (B2+B3).…”

Section: Introductionmentioning

confidence: 99%

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A perfect power-law spectrum even at the highest frequencies: The Toothbrush relic

Rajpurohit

Vazza

Hoeft

et al. 2020

A&A

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Radio relics trace shock fronts generated in the intracluster medium (ICM) during cluster mergers. The particle acceleration mechanism at the shock fronts is not yet completely understood. We observed the Toothbrush relic with the Effelsberg and Sardinia Radio Telescope at 14.25 GHz and 18.6 GHz, respectively. Unlike previously claimed, the integrated spectrum of the relic closely follows a power law over almost three orders of magnitude in frequency, with a spectral index of α58 MHz18.6 GHz = −1.16 ± 0.03. Our finding is consistent with a power-law injection spectrum, as predicted by diffusive shock acceleration theory. The result suggests that there is only little magnetic field strength evolution downstream of the shock. From the lack of spectral steepening, we find that either the Sunyaev–Zeldovich decrement produced by the pressure jump is less extended than ∼600 kpc along the line of sight or, conversely, that the relic is located far behind in the cluster. For the first time, we detect linearly polarized emission from the “brush” at 18.6 GHz. Compared to 8.3 GHz, the degree of polarization across the brush increases at 18.6 GHz, suggesting a strong Faraday depolarization toward lower frequencies. The observed depolarization is consistent with an intervening magnetized screen that arises from the dense ICM containing turbulent magnetic fields. The depolarization, corresponding to a standard deviation of the rotation measures as high as σRM = 212 ± 23 rad m−2, suggests that the brush is located in or behind the ICM. Our findings indicate that the Toothbrush relic can be consistently explained by the standard scenario for relic formation.

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Section: Integrated Spectrumsupporting

confidence: 92%

Section: Integrated Spectrummentioning

confidence: 91%

Section: Integrated Spectrummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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A perfect power-law spectrum even at the highest frequencies: The Toothbrush relic

Rajpurohit

Vazza

Hoeft

et al. 2020

A&A

Self Cite

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CAPTURE: a continuum imaging pipeline for the uGMRT

Kale

Ishwara‐Chandra

2020

Exp Astron

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MWA and ASKAP observations of atypical radio-halo-hosting galaxy clusters: Abell 141 and Abell 3404

Duchesne

Johnston‐Hollitt

Wilber

2021

Publ. Astron. Soc. Aust.

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We report on the detection of a giant radio halo in the cluster Abell 3404 as well as confirmation of the radio halo observed in Abell 141 (with linear extents $\sim\!770$ and $\sim\!850$ kpc, respectively). We use the Murchison Widefield Array, the Australian Square Kilometre Array Pathfinder, and the Australia Telescope Compact Array to characterise the emission and intervening radio sources from $\sim100$ to 1 000 MHz; power law models are fit to the spectral energy distributions with spectral indices $\alpha_{88}^{1\,110} = -1.66 \pm 0.07$ and $\alpha_{88}^{943} = -1.06 \pm 0.09$ for the radio halos in Abell 3404 and Abell 141, respectively. We find strong correlation between radio and X-ray surface brightness for Abell 3404 but little correlation for Abell 141. We note that each cluster has an atypical morphology for a radio-halo-hosting cluster, with Abell 141 having been previously reported to be in a pre-merging state, and Abell 3404 is largely relaxed with only minor evidence for a disturbed morphology. We find that the radio halo powers are consistent with the current radio halo sample and $P_\nu$ –M scaling relations, but note that the radio halo in Abell 3404 is an ultra-steep–spectrum radio halo (USSRH) and, as with other USSRHs lies slightly below the best-fit $P_{1.4}$ –M relation. We find that an updated scaling relation is consistent with previous results and shifting the frequency to 150 MHz does not significantly alter the best-fit relations with a sample of 86 radio halos. We suggest that the USSRH halo in Abell 3404 represents the faint class of radio halos that will be found in clusters undergoing weak mergers.

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New mysteries and challenges from the Toothbrush relic: wideband observations from 550 MHz to 8 GHz

Cited by 71 publications

References 90 publications

A perfect power-law spectrum even at the highest frequencies: The Toothbrush relic

A perfect power-law spectrum even at the highest frequencies: The Toothbrush relic

CAPTURE: a continuum imaging pipeline for the uGMRT

MWA and ASKAP observations of atypical radio-halo-hosting galaxy clusters: Abell 141 and Abell 3404

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