J/A+A/634/A9ivo://CDS.VizieR/J/A+A/634/A9doi:10.26093/cds/vizier.36340009CDSMaccagni F.M.Murgia M.Serra P.Govoni F.Morokuma-Matsui K.,Kleiner D.Buchner S.Jozsa G.I.G.Kamphuis P.Makhathini S.,Molnar D.Cs.Prokhorov D.A.Ramaila A.Ramatsoku M.Thorat K.,Smirnov O.2020-05-05T12:20:46Z2020-01-28T08:07:54ZCDS support team

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

cds-question@unistra.frradio-galaxiesradio-sourcesWe present new observations of Fornax A taken at ~1GHz with the MeerKAT telescope and at ~6GHz with the Sardinia Radio Telescope (SRT). The sensitive (noise ~16uJy/beam), high-resolution (<10'') MeerKAT images show that the lobes of Fornax A have a double-shell morphology, where dense filaments are embedded in a diffuse and extended cocoon. We study the spectral properties of these components by combining the MeerKAT and SRT observations with archival data between 84MHz and 217GHz. For the first time, we show that multiple episodes of nuclear activity must have formed the extended radio lobes. The modelling of the radio spectrum suggests that the last episode of injection of relativistic particles into the lobes started ~24Myr ago and stopped 12Myr ago. More recently (~3Myr ago), a less powerful and short (<1Myr) phase of nuclear activity generated the central jets. Currently, the core may be in a new active phase. It appears that Fornax A is rapidly flickering. The dense environment around Fornax A has lead to a complex recent merger history for this galaxy, including mergers spanning a range of gas contents and mass ratios, as shown by the analysis of the galaxy's stellar- and cold-gas phases. This complex recent history may be the cause of the rapid, recurrent nuclear activity of Fornax A.2020A&A...634A...9Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/634/A9CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/634/A9https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/634/A9http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/634/A9https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/634/A9https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/634/A9http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/634/A9GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/634/A9/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/634/A9/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/634/A9/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/634/A9/list?GETtext/xml+votable180.050000true50.67403-37.208060.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/634/A96/34493https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/634/A9?format=asciiRadiodefaultJ/A+A/634/A9/tableb1Flux densities of Fornax A between 84MHz and 217GHzn_FreqNote (1)meta.notechare_FluxDensPer? Percentage error on flux density%stat.errorintnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFreqFrequency of measured flux density of Fornax AGHzem.freqdoubleFluxDens? Flux density measured in this workJyphot.flux.densityfloatnullableu_FluxDens[)] Uncertainty flag on FluxDensmeta.code.errorchare_FluxDens? Error on flux densityJystat.errorfloatnullableFluxDensMcK? Flux density measured by McKinley et al. 2015MNRAS.446.3478MJyphot.flux.densityfloatnullablee_FluxDensMcK? Percentage error on flux density%stat.errorintnullableFluxDensPer? Flux density measured by Perley et al. 2017ApJS..230....7P, Cat. J/ApJS/230/7Jyphot.flux.densityintnullableRefTelescope used for the measurements, or the reference to the published fluxesmeta.notecharJ/A+A/634/A9/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