J/A+A/669/A1ivo://CDS.VizieR/J/A+A/669/A1doi:10.26093/cds/vizier.36690001CDSRajpurohit K.Osinga E.Brienza M.Botteon A.Brunetti G.Forman W.R.,Riseley C.J.Vazza F.Bonafede A.van Weeren R.J.Brueggen M.,Rajpurohit S.Drabent A.Dallacasa D.Rossetti M.Rajpurohit A.S.,Hoeft M.Bonnassieux E.Cassano R.Miley G.K.2023-01-18T06:39:49Z2022-12-22T16:10:16ZCDS support team

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

cds-question@unistra.frgalaxy-clustersradio-sourcesWe present the first detailed analysis of the radio halo in the merging galaxy cluster Abell 2256 using the LOw Frequency ARray, the upgraded Giant Metrewave Radio Telescope, and the Karl G. Jansky Very Large Array. Radio observations (120MHz-2GHz) combined with archival Chandra and XMM-Newton X-ray data allowed us to study the central radio halo emission with unprecedented detail. The integrated radio emission from the entire halo is characterized by an ultra-steep spectrum, which can be described by a power law with alpha_144MHz_^1.5GHz^=-1.63+/-0.03 and radial steepening in the outer regions. The halo is significantly underluminous according to the current scaling relations between radio power and mass at 1.4GHz, not at 150MHz; ultra-steep spectrum halos are predicted to be statistically underluminous. Despite the complex structure of this system, the halo morphology is remarkably similar to that of the X-ray emission. The radio surface brightness distribution across the halo is strongly correlated with the X-ray brightness of the intracluster medium (ICM). The derived correlations show sublinear slopes and distinct structures: the core is I_R_{prop.to}I_X_^1.51^, the outermost region I_R_{prop.to}I_X_^0.41^, and we find radio morphological connections with X-ray discontinuities. We also find a strong anticorrelation between the radio spectral index and the X-ray surface brightness, implying radial steepening. We suggest that the halo core is either related to old plasma from previous active galactic nuclei activity, being advected, compressed, and reaccelerated by mechanisms activated by the cold front or less turbulent with strong magnetic field in the core. The change in the radio versus X-ray correlation slopes in the outer regions of the halo could be due to a radial decline of the magnetic field, the increase in the number density of seed particles, or increasing turbulence. Our findings suggest that the emitting volume is not homogenous according to turbulent reacceleration models.2023A&A...669A...1Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/669/A1CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/123/2261 : Radial velocities in A2256 (Berrington+, 2002)J/AJ/125/2393 : A2256 galaxies redshifts and 1.4GHz fluxes (Miller+, 2003)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/669/A1https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/669/A1http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/669/A1https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/669/A1https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/669/A1http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/669/A1GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/669/A1/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/669/A1/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/669/A1/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/669/A1/list?GETtext/xml+votable180.050000true255.9431178.719850.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/669/A16/12121https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/669/A1?format=asciiRadiodefaultJ/A+A/669/A1/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;obsnullablesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharAssocDataAssociated Data web pagemeta.ref.urlchar