The Planck clusters in the LOFAR sky. I. LoTSS-DR2: new detections and sample overview

Botteon, A.; Shimwell, T. W.; Cassano, R.; Cuciti, V.; Zhang, X.; Bruno, L.; Camillini, L.; Natale, R.; Jones, A.; Gastaldello, F.; Simionescu, A.; Rossetti, M.; Akamatsu, H.; van Weeren, R. J.; Brunetti, G.; Brüggen, M.; Groenveld, C.; Hoang, D. N.; Hardcastle, M. J.; Ignesti, A.; Di Gennaro, G.; Bonafede, A.; Drabent, A.; Röttgering, H. J. A.; Hoeft, M.; de Gasperin, F.

doi:10.48550/arxiv.2202.11720

Cited by 2 publications

(17 citation statements)

References 150 publications

(164 reference statements)

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“…In the South-West, a roundish patch of emission (A) is observed, without a clear optical counterpart. North-West of source A, we clearly detect a source which resembles a radio relic, as already hinted at in VW21 and Botteon et al (2022). From this image, it is not clear whether the putative relic and source A are part of the same structure.…”

Section: Hba and Lba Comparisonmentioning

confidence: 51%

“…Extended emission was already claimed by Govoni et al (2012) through 1.4 GHz Very Large Array (VLA) data in D and C configuration. LOFAR observations at 144 MHz confirm the presence of diffuse emission (VW21, Botteon et al 2022), albeit on a greater scale of 1.8 Mpc. The difference in size is due to the high sensitivity and low frequency coverage of LOFAR.…”

Section: Introductionmentioning

confidence: 76%

“…In this work, we exploit the same datasets which were recently presented in Botteon et al (2022). New images were produced through WSClean with different sets of parameters, depending on our purposes, applying multiple weighting schemes and visibility tapering.…”

Section: Hba Observationsmentioning

confidence: 99%

“…New images were produced through WSClean with different sets of parameters, depending on our purposes, applying multiple weighting schemes and visibility tapering. The flux density scale was aligned with the LoTSS-DR2 data release (Botteon et al 2022), where the flux calibration uncertainty is estimated to be ∼10% (Hardcastle et al 2021). Where explicited, compact-source subtraction was performed exploiting the same method described in Sec.…”

Section: Hba Observationsmentioning

confidence: 99%

“…As already discussed in VW21, it lies in front (at least in projection) of a group of galaxies with the same redshift of A1550. Low-resolution images at 144 MHz showed that it is likely connected to the halo (VW21 and Botteon et al 2022). We will return on this throughout this paper.…”

Section: Hba and Lba Comparisonmentioning

confidence: 99%

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Particle re-acceleration and diffuse radio sources in the galaxy cluster Abell 1550

Pasini,

Edler,

Brüggen

et al. 2022

Preprint

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Context. Radio observations of galaxy clusters reveal a plethora of diffuse, steep-spectrum sources related to the re-acceleration of cosmic-ray electrons, such as halos, relics and phoenices. In this context, the LOFAR LBA Sky Survey provides the most sensitive images of the sky at 54 MHz to date, allowing to investigate re-acceleration processes in a poorly-explored frequency regime. Aims. We study diffuse radio emission in the galaxy cluster Abell 1550, with the aim of constraining particle re-acceleration in the intra-cluster medium. Methods. We exploit observations at four different radio frequencies: 54, 144, 400 and 1400 MHz. To complement our analysis, we make use of archival Chandra X-ray data.Results. At all frequencies we detect an ultra-steep spectrum radio halo (S ν ∝ ν −1.6 ) with an extent of ∼ 1.2 Mpc at 54 MHz. Its morphology follows the distribution of the thermal intra-cluster medium inferred from the Chandra observation. West of the centrally located head-tail radio galaxy, we detect a radio relic with a projected extent of ∼ 500 kpc. From the relic, a ∼600 kpc long bridge departs and connect it with the halo. Between the relic and the radio galaxy, we observe what is most likely a radio phoenix, given its curved spectrum. The phoenix is connected to the tail of the radio galaxy through two arms, which show a nearly constant spectral index for ∼ 300 kpc. Conclusions. The halo could be produced by turbulence induced by a major merger, with the merger axis lying in the NE-SW direction. This is supported by the position of the relic, whose origin could be attributed to a shock propagating along the merger axis. It is possible that the same shock has also produced the phoenix through adiabatic compression, while we propose that the bridge could be generated by electrons which were pre-accelerated by the shock, and then re-accelerated by turbulence. Finally, we detect hints of gentle re-energisation in the two arms which depart from the tail of the radio galaxy.

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Section: Hba and Lba Comparisonmentioning

confidence: 51%

Section: Introductionmentioning

confidence: 76%

Section: Hba Observationsmentioning

confidence: 99%

Section: Hba Observationsmentioning

confidence: 99%

Section: Hba and Lba Comparisonmentioning

confidence: 99%

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Particle re-acceleration and diffuse radio sources in the galaxy cluster Abell 1550

Pasini,

Edler,

Brüggen

et al. 2022

Preprint

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Abell 1033: Radio halo and gently reenergized tail at 54 MHz

Edler

Gasperin

Brunetti

et al. 2022

A&A

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Context. Abell 1033 is a merging galaxy cluster of moderate mass (M 500 = 3.24 × 10 14 M ) which hosts a broad variety of diffuse radio sources linked to different astrophysical phenomena. The most peculiar one is an ultra-steep spectrum elongated feature which is the prototype of the category of gently re-energized tails (GReET). Furthermore, the cluster hosts sources previously classified as a radio phoenix and a radio halo. Aims. In this work, we aim to improve the understanding of the cosmic ray acceleration mechanisms in galaxy clusters in a frequency and mass range poorly explored so far. Methods. To investigate the ultra-steep synchrotron emission in the cluster, we perform a full direction-dependent calibration of a LOFAR observation centered at 54 MHz. We analyze this observation together with re-calibrated data of the LOFAR Two-meter Sky Survey at 144 MHz and an archival GMRT observation at 323 MHz. We perform a spectral study of the radio galaxy tail connected to the GReET to test if the current interpretation of the source is in agreement with observational evidence below 100 MHz. Additionally, we employ a Markov chain Monte Carlo code to fit the halo surface-brightness profile at different frequencies. Results. We report an extreme spectral curvature for the GReET, the spectral index flattens from α 323MHz 144MHz ≈ −4 to α 144MHz 54MHz ≈ −2. This indicates the presence of a cut-off in the electron energy spectrum. At the cluster center, we detect the radio halo at 54, 144 and at lower significance at 323 MHz. We categorize it as an ultra-steep spectrum radio halo with a low-frequency spectral index α = −1.65 ± 0.17. Additionally, with a radio power of P 150 MHz = 1.22 ± 0.13 × 10 25 W Hz −1 , it is found to be significantly above the radio power-to-cluster mass correlations reported in the literature. Furthermore, the synchrotron spectrum of the halo is found to further steepen between 144 and 323 MHz, in agreement with the presence of a break in the electron spectrum, which is a prediction of homogeneous re-acceleration models.

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The Planck clusters in the LOFAR sky. I. LoTSS-DR2: new detections and sample overview

Cited by 2 publications

References 150 publications

Particle re-acceleration and diffuse radio sources in the galaxy cluster Abell 1550

Particle re-acceleration and diffuse radio sources in the galaxy cluster Abell 1550

Abell 1033: Radio halo and gently reenergized tail at 54 MHz

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