Low-frequency radio study of MACS clusters at 610 and 235 MHz using the GMRT

Paul, Surajit; Salunkhe, Sameer; Datta, Abhirup; Intema, H. T.

doi:10.1093/mnras/stz1965

Cited by 14 publications

(25 citation statements)

References 63 publications

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“…At Band 4, with a restoring beam width of 5 we achieved a noise level of 7µ Jy beam −1 . Our new uGMRT Band 3 and Band 4 images are about a factor of ten deeper than the published VLA and GMRT images at the same frequency (Orrú et al 2007;Venturi et al 2013;Paul et al 2019).…”

Section: Results: Radio Continuum Imagesmentioning

confidence: 47%

“…It is known to host a giant ∼ 2.1 Mpc large radio halo at the cluster center and a 1.5 Mpc relic to the north-east. (Giovannini et al 1999;Govoni et al 2001a,b;Orrú et al 2007;Venturi et al 2013;Pearce et al 2017;George et al 2017;Paul et al 2019). With deep VLA observations, Pearce et al (2017) found three new faint radio relics (namely, R2, R3, and R4) in this system, see Fig.…”

Section: Abell 2744mentioning

confidence: 82%

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Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis

Rajpurohit,

Vazza,

van Weeren

et al. 2021

Preprint

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We report upgraded Giant Metrewave Radio Telescope observations of the massive and highly disturbed galaxy cluster Abell 2744. The cluster is experiencing a very complex multiple merger and hosts a giant halo and four radio relics. To study the spectral and polarization properties, and radio versus X-ray correlations of the diffuse sources, we complement our analysis with existing VLA (1-4 GHz) and Chandra observations. In our new images, the central halo emission is observed to be more extended than detected previously. The integrated spectrum of the halo follows a power-law between 150 MHz and 3 GHz, while its subregions show significantly different spectra also featuring high frequency spectral steepening. Our results highlight that an overall power-law spectrum, as observed in many radio halos, may also arise from the superposition of different subcomponents. The radio brightness distribution of the halo strongly correlates with the X-ray brightness of the intracluster medium (ICM) with a constant sublinear slope from 675 MHz to 3 GHz. The comparison of the spectral index with the X-ray brightness and temperature reveals different trends indicating that the halo consists of two main components with distinct evolutionary signatures, possibly related to different cluster subcomponents. All four relics in this system follow a power-law radio spectrum, compatible with shocks with Mach number in the range 3.0 − 4.5. All relics are also highly polarized between 1 − 4 GHz and show Faraday dispersion measures below 10 rad m −2 , suggesting that they are located in the low density ICM. The complexity in the distribution and properties of nonthermal components in Abell 2744 support a multiple merger scenario, as also highlighted by previous X-ray and lensing studies. Our results demonstrate the importance of sensitive and high-resolution, multi-frequency radio observations for understanding the interplay between the thermal and non-thermal components of the ICM.

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Section: Results: Radio Continuum Imagesmentioning

confidence: 47%

Section: Abell 2744mentioning

confidence: 82%

Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis

Rajpurohit,

Vazza,

van Weeren

et al. 2021

Preprint

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“…For ZwCl 1742.1+3306, the observations were not sufficient to be sure of its nature. However, Paul et al (2019) confirmed the presence of a significant extra diffuse emission surrounding the BCG at the centre of the cluster MACS J1931.8−2634 using GMRT radio observations at 235 and 610 MHz, and we therefore now consider this source as a confirmed mini-halo. We retain the total flux density from Giacintucci et al (2014a) as Paul et al (2019) found the total flux density at 235 and 610 MHz and not at 1.4 GHz.…”

Section: Cluster Samplesupporting

confidence: 52%

On the relation between mini-halos and AGN feedback in clusters of galaxies

Richard-Laferrière,

Hlavacek-Larrondo,

Nemmen

et al. 2020

Preprint

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A variety of large-scale diffuse radio structures have been identified in many clusters with the advent of new state-of-the-art facilities in radio astronomy. Among these diffuse radio structures, radio mini-halos are found in the central regions of cool core clusters. Their origin is still unknown and they are challenging to discover; less than thirty have been published to date. Based on new VLA observations, we confirmed the mini-halo in the massive strong cool core cluster PKS 0745−191 (z = 0.1028) and discovered one in the massive cool core cluster MACS J1447.4+0827 (z = 0.3755). Furthermore, using a detailed analysis of all known mini-halos, we explore the relation between mini-halos and AGN feedback processes from the central galaxy. We find evidence of strong, previously unknown correlations between mini-halo radio power and X-ray cavity power, and between mini-halo and the central galaxy radio power related to the relativistic jets when spectrally decomposing the AGN radio emission into a component for past outbursts and one for on-going accretion. Overall, our study indicates that mini-halos are directly connected to the central AGN in clusters, following previous suppositions. We hypothesize that AGN feedback may be one of the dominant mechanisms giving rise to mini-halos by injecting energy into the intra-cluster medium and reaccelerating an old population of particles, while sloshing motion may drive the overall shape of mini-halos inside cold fronts. AGN feedback may therefore not only play a vital role in offsetting cooling in cool core clusters, but may also play a fundamental role in re-energizing non-thermal particles in clusters.

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“…For example, the relic at Abell 2744 (e.g. Govoni et al 2001;Eckert et al 2016;Pearce et al 2017;Paul et al 2019) reaches a surface brightness of the order of tens of mJy beam −1 at 1.4 GHz, which would require an acceleration efficiency of η ∼ 1 in our L/4 turbulence.…”

Section: S U M M a Ry A N D C O N C L U S I O N Smentioning

confidence: 99%

Morphology of radio relics – I. What causes the substructure of synchrotron emission?

Domínguez-Fernández

Brüggen

Vazza

et al. 2020

Monthly Notices of the Royal Astronomical Society

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High-resolution radio observations of cluster radio relics often show complex spatial and spectral features. However, it is not clear what these features reveal about the underlying magnetic field properties. We performed three-dimensional magneto-hydrodynamical simulations of merger shock waves propagating through a magnetised, turbulent intracluster medium. Our model includes the diffusive shock acceleration of cosmic-ray electrons, their spatial advection and energy losses at run-time. With this set-up we can investigate the relation between radio substructure and pre-shock plasma conditions in the host cluster. We find that upstream turbulence plays a major role in shaping the properties of radio relics produced downstream. Within the assumption of diffusive shock acceleration, we can reproduce the observed discrepancy between the X-ray derived Mach number of shocks, and the Mach number inferred from radio spectra. Our simulated spectral index maps and profiles across the radio relic also suggest that the standard deviation of the upstream magnetic field must be relatively small (σB ≤ 1 μG) in order to reproduce observations and therefore, radio relics can potentially constrain the distribution of magnetic fields in galaxy clusters outskirts.

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Low-frequency radio study of MACS clusters at 610 and 235 MHz using the GMRT

Cited by 14 publications

References 63 publications

Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis

Dissecting nonthermal emission in the complex multiple-merger galaxy cluster Abell 2744: Radio and X-ray analysis

On the relation between mini-halos and AGN feedback in clusters of galaxies

Morphology of radio relics – I. What causes the substructure of synchrotron emission?

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