J/A+A/693/A172ivo://CDS.VizieR/J/A+A/693/A172doi:10.26093/cds/vizier.36930172CDSRicci L.Boccardi B.Roeder J.Perucho M.Mattia G.Kadler M.,Benke P.Bartolini V.Krichbaum T.P.Madika E.2025-03-07T20:01:04Z2025-01-14T08:46:44ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiradio-galaxiesvery-long-baseline-interferometryThe dynamic of relativistic jets in the inner parsec regions is deeply affected by the nature of the magnetic fields. The level of magnetization of the plasma, as well as the geometry of these fields on compact scales, have not yet been fully constrained. In this paper we employ multi-frequency and multi-epoch very long baseline interferometry observations of the nearby radio galaxy NGC 315. We aim to derive insights into the magnetic field properties on sub-parsec and parsec scales by examining observational signatures such as the spectral index, synchrotron turnover frequency, and brightness temperature profiles. This analysis is performed by considering the properties of the jet acceleration and collimation zone, which can be probed thanks to the source vicinity, as well as the inner part of the jet conical region. We observe remarkably steep values for the spectral index on sub-parsec scales (similar to -2) which flatten around -0.8 on parsec scales. We suggest that the observed steep values may result from particles being accelerated via diffusive shock acceleration mechanisms in magnetized plasma and subsequently experiencing cooling through synchrotron losses. The brightness temperature of the 43GHz cores indicates a dominance of the magnetic energy at the jet base, while the cores at progressively lower frequencies reveal a gradual transition towards equipartition. Based on the spectral index and brightness temperature along the incoming jet, and by employing theoretical models, we derive that the magnetic field strength has a close-to-linear dependence with distance going from parsec scales up to the jet apex.2025A&A...693A.172Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/693/A172CatalogResearchIsServedByTAP 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/A172https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/693/A172http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/693/A172https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/693/A172https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/693/A172http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/693/A172GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/693/A172/list (List of fits maps)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/693/A172/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/693/A172/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/693/A172/list?GETtext/xml+votable180.050000true14.4536830.352450.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/693/A1726/2214https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/693/A172?format=asciiRadiodefaultJ/A+A/693/A172/listList of fits mapsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFreqObserving frequency (from table 1)GHzem.freqfloatPCodeProject code (from table 1)meta.codecharBeam1Beam size, major axis (from table 1)masphys.angSize;instr.beamfloatBeam2Beam size, minor axis (from table 1)masphys.angSize;instr.beamfloatPA[] Beam size, position angle (from table 1)degpos.posAng;instr.beamfloatFtotTotal flux density (from table 1)Jyphot.flux.density;em.radiofloatFpeakBrightness peak value (from table 1)Jy/beamphot.flux.density;em.radiofloatrmsThermal noise (from table 1)Jy/beamstat.snr;instr.det.noisefloatRAJ2000Right 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.fitschar