Revived fossil plasma sources in galaxy clusters

Mandal, S.; Intema, H. T.; Weeren, R. J. van; Shimwell, T. W.; Botteon, A.; Brunetti, G.; Gasperin, F. de; Brüggen, M.; Gennaro, G. Di; Kraft, Ralph; Röttgering, H. J. A.; Hardcastle, M. J.; Tasse, C.

doi:10.1051/0004-6361/201936560

Cited by 48 publications

(57 citation statements)

References 79 publications

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“…We interpreted the presence of edge-brightened features as indication of a role played by the ICM dynamics in the origin of this radio source. Interestingly, the radio spectral properties of the Kite resemble those of the radio phoenix sources, an exotic class of diffuse radio sources produced by the interplay of fossil radio plasma with shocks and/or ICM motions (e.g., Clarke et al 2013;Mandal et al 2020). Specifically, the arcs of the Kite resemble the complex, filamentary radio morphology of the radio phoenices, whose filaments have patchy distributions of increased surface brightness, and synchrotron emission typically that follow a curved spectra.…”

Section: The Role Of the Icm Dynamicsmentioning

confidence: 98%

The great Kite in the sky: A LOFAR observation of the radio source in Abell 2626

Ignesti

Shimwell

Brunetti

et al. 2020

A&A

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Context. The radio source at the center of the galaxy cluster Abell 2626, also known as the Kite, stands out for its unique morphology composed of four symmetric arcs. Previous studies have probed the properties of this source at different frequencies and its interplay with the surrounding thermal plasma, but the puzzle of its origin is still unsolved. Aims. We use a new LOw-Frequency ARray (LOFAR) observation from the LOFAR Two-meter Sky Survey at 144 MHz to investigate the origin of the Kite. Methods. We present a detailed analysis of the new radio data, which we combined with archival radio and X-ray observations. We produced a new, resolved spectral index map of the source with a resolution of 7″ and we studied the spatial correlation of radio and X-ray emission to investigate the interplay between thermal and nonthermal plasma. Results. The new LOFAR data changed our view of the Kite because we discovered two steep-spectrum (α < −1.5) plumes of emission connected to the arcs. The spectral analysis shows, for the first time, a spatial trend of the spectrum along the arcs with evidence of curved synchrotron spectra and a spatial correlation with the X-ray surface brightness. On the basis of our results, we propose that the Kite was originally an X-shaped radio galaxy whose fossil radio plasma, after the end of the activity of the central active galactic nucleus, has been compressed as a consequence of motions of the thermal plasma encompassing the galaxy. The interplay between the compression and advection of the fossil plasma, with the restarting of the nuclear activity of the central galaxy, could have enhanced the radio emission of the fossil plasma producing the arcs of the Kite. We also present the first, low-frequency observation of a jellyfish galaxy in the same field, in which we detect extended, low-frequency emission without a counterpart at higher frequencies.

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Section: The Role Of the Icm Dynamicsmentioning

confidence: 98%

The great Kite in the sky: A LOFAR observation of the radio source in Abell 2626

Ignesti

Shimwell

Brunetti

et al. 2020

A&A

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“…Enßlin & Gopal-Krishna 2001), forming the so-called radio phoenixes (e.g. Slee et al 2001;Cohen & Clarke 2011;van Weeren et al 2011;Kale & Dwarakanath 2012;Mandal et al 2020); moreover, the possible connection between the T-bone and Original TRG could also indicate the presence of a Gently Re-Energized Tail (GReET; de Gasperin et al 2017). Regardless of their precise origin, the existence of "radio ghosts" in the ICM (i.e.…”

Section: Surface Brightness Propertiesmentioning

confidence: 99%

The Beautiful Mess in Abell 2255

Botteon

Brunetti

Weeren

et al. 2020

ApJ

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We present LOFAR observations of one of the most spectacular objects in the radio sky: Abell 2255. This is a nearby (z = 0.0806) merging galaxy cluster hosting one of the first radio halos ever detected in the intra-cluster medium (ICM). The deep LOFAR images at 144 MHz of the central ∼ 10 Mpc 2 region show a plethora of emission on different scales, from tens of kpc to above Mpc sizes. In this work, we focus on the innermost region of the cluster. Among the numerous interesting features observed, we discover remarkable bright and filamentary structures embedded in the radio halo. We incorporate archival WSRT 1.2 GHz data to study the spectral properties of the diffuse synchrotron emission and find a very complex spectral index distribution in the halo spanning a wide range of values. We combine the radio data with Chandra observations to investigate the connection between the thermal and non-thermal components by quantitatively comparing the radio and X-ray surface brightness and the spectral index of the radio emission with the thermodynamical quantities of the ICM. Despite the multitude of structures observed in the radio halo, we find that the X-ray and radio emission are overall well correlated. The fact that the steepest spectrum emission is located in the cluster center and traces regions with high entropy possibly suggests the presence of seed particles injected by radio galaxies that are spread in the ICM by turbulence generating the extended radio halo.

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“…Sources of this type can have spectral indices as steep as α = −4 (e.g. Gently Re-Energised Tails de Gasperin et al 2017 or radio Phoenixes Mandal et al 2020). Since the LBA system is nearly ten times more sensitive than HBA for such steep spectra, LOFAR LBA is the only instrument able to efficiently detect this new population of elusive sources.…”

Section: Galaxy Clusters and Large-scale Structurementioning

confidence: 99%

The LOFAR LBA Sky Survey

Gasperin

Williams

Best

et al. 2021

A&A

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Context. The LOw Frequency ARray (LOFAR) is the only radio telescope that is presently capable of high-sensitivity, high-resolution (i.e. < 1 mJy beam −1 and < 15) observations at ultra-low frequencies (< 100 MHz). To utilise these capabilities, the LOFAR Surveys Key Science Project is undertaking a large survey to cover the entire northern sky with Low Band Antenna (LBA) observations. Aims. The LOFAR LBA Sky Survey (LoLSS) aims to cover the entire northern sky with 3170 pointings in the frequency range between 42 − 66 MHz, at a resolution of 15 and at a sensitivity of 1 mJy beam −1 (1σ). In this work, we outline the survey strategy, the observational status, and the calibration techniques. We also briefly describe several of our scientific motivations and present the preliminary public data release. Methods. The preliminary images were produced using a fully automated pipeline aimed at correcting all direction-independent effects in the data. Whilst the direction-dependent effects, such as those from the ionosphere, have not yet been corrected, the images presented in this work are still ten times more sensitive than previous available surveys at these low frequencies. Results. The preliminary data release covers 740 deg 2 around the HETDEX spring field region at an angular resolution of 47 with a median noise level of 5 mJy beam −1. The images and the catalogue of 25,247 sources have been publicly released. We demonstrate that the system is capable of reaching a root mean square (rms) noise of 1 mJy beam −1 and an angular resolution of 15 once directiondependent effects are accounted for. Conclusions. LoLSS will provide the ultra-low-frequency information for hundreds of thousands of radio sources, providing critical spectral information and producing a unique data set that can be used for a wide range of science topics, such as the search for high redshift galaxies and quasars, the study of the magnetosphere of exoplanets, and the detection of the oldest populations of cosmic-rays in galaxies, clusters of galaxies, as well as those produced by active galactic nuclei (AGN).

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Revived fossil plasma sources in galaxy clusters

Cited by 48 publications

References 79 publications

The great Kite in the sky: A LOFAR observation of the radio source in Abell 2626

The great Kite in the sky: A LOFAR observation of the radio source in Abell 2626

The Beautiful Mess in Abell 2255

The LOFAR LBA Sky Survey

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