J/A+A/693/A99ivo://CDS.VizieR/J/A+A/693/A99doi:10.26093/cds/vizier.36930099CDSGroeneveld C.van Weeren R.J.Botteon A.Cassano R.de Gasperin F.,Osinga E.Brunetti G.Roettgering H.J.A.2025-03-07T20:01:11Z2025-01-07T09:19:55ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxy-clustersradio-sourcesSome galaxy clusters contain non-thermal synchrotron emitting plasma permeating the intracluster medium (ICM). The spectral properties of this radio emission are not well characterized at decameter wavelengths ({nu}<30MHz), primarily due to the severe corrupting effects of the ionosphere. Using a recently developed calibration strategy, we present LOFAR images below 30MHz of the low mass galaxy cluster Abell 655, which was serendipitously detected in an observation of the bright calibrator 3C 196. We combine this observation with LOFAR data at 144MHz, and new Band 4 Giant Metrewave Radio Telescope observations centered at 650MHz. In the 15-30MHz LOFAR image, diffuse emission is seen with a physical extent of about 700kpc. We argue that the diffuse emission detected in this galaxy cluster likely has multiple origins. At higher frequencies (650MHz), the diffuse emission resembles a radio halo, while at lower frequencies the emission seems to consist of several components and bar-like structures. It suggests that most low-frequency emission in this cluster comes from re-energized fossil plasma from old AGN outbursts, coexisting with the radio halo component. By counting the number of cluster radio detections in the decameter band, we estimate that around a quarter of the Planck clusters host re-energised fossil plasma that is detectable in the decameter band with LOFAR.2025A&A...693A..99Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/693/A99CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/693/A99https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/693/A99http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/693/A99https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/693/A99https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/693/A99http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/693/A99GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/693/A99/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/693/A99/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/693/A99/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/693/A99/list?GETtext/xml+votable180.050000true126.3692347.13320.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/693/A996/6609 6611https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/693/A99?format=asciiRadiodefaultJ/A+A/693/A99/listList of fits imagesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableFreqObservation frequencyMHzem.freq;obsdoublesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar