J/ApJ/952/34ivo://CDS.VizieR/J/ApJ/952/34doi:10.26093/cds/vizier/ba-xr-12CDSKim J.-Y.Savolainen T.Voitsik P.Kravchenko E.V.Lisakov M.M.,Kovalev Y.Y.Muller H.Lobanov A.P.Sokolovsky K.V.Bruni G.,Edwards P.G.Reynolds C.Bach U.Gurvits L.I.Krichbaum T.P.Hada K.,Giroletti M.Orienti M.Anderson J.M.Lee S.-S.Sohn B.W.,Zensus J.A.2026-07-02T12:00:06Z2025-09-26T13:15:58ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiradio-galaxiesinterferometryradio-astronomyWe present results from the first 22GHz space very long baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in 2014 February at 22GHz with 21 ground stations, reaching projected (u, v) spacings up to ~11G{lambda}. The imaging experiment was complemented by snapshot RadioAstron data of M87 obtained during 2013-2016 from the AGN Survey Key Science Program. Their longest baselines extend up to ~25G{lambda}. For all of these measurements, fringes are detected only up to ~2.8 Earth diameter or ~3G{lambda} baseline lengths, resulting in a new image with angular resolution of ~150{mu}as or ~20 Schwarzschild radii spatial resolution. The new image not only shows edge-brightened jet and counterjet structures down to submilliarcsecond scales but also clearly resolves the VLBI core region. While the overall size of the core is comparable to those reported in the literature, the ground-space fringe detection and slightly superresolved RadioAstron image suggest the presence of substructures in the nucleus, whose minimum brightness temperature exceeds T_B,min_~10^12^K. It is challenging to explain the origin of this record-high T_B,min_ value for M87 by pure Doppler boosting effect with a simple conical jet geometry and known jet speed. Therefore, this can be evidence for more extreme Doppler boosting due to a blazar-like small jet viewing angle or highly efficient particle acceleration processes occurring already at the base of the outflow.2023ApJ...952...34Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/952/34CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/MNRAS/313/469 : Streaming motions of galaxy clusters. I. (Smith+, 2000)J/AJ/130/2473 : Fine-scale structure at 15GHz (Kovalev+, 2005)J/AJ/136/159 : 86GHz VLBI survey of compact radio sources (Lee+, 2008)J/AJ/138/1874 : MOJAVE. VI. Kinematics of blazar jets (Lister+, 2009)J/AJ/142/35 : The VLBA Galactic Plane Survey (VGaPS) (Petrov+, 2011)J/A+A/545/A113 : MOJAVE IX. Core shift effects (Pushkarev+, 2012)J/ApJ/846/98 : Jet kinematics of blazars at 43GHz (Jorstad+, 2017)J/MNRAS/468/4992 : MOJAVE XIV. AGN jets & opening angles (Pushkarev+, 2017)J/A+A/616/A188 : M87 jet VLBI images (Kim+, 2018)J/ApJ/866/137 : Bright blazars var. brightness temp. (Liodakis+, 2018)J/ApJS/234/12 : MOJAVE XV. 15GHz obs. of AGN jets 1996-2016 (Lister+, 2018)J/A+A/622/A92 : Ultracompact extragal. radio sources at 86GHz (Nair+, 2019)J/MNRAS/485/1822 : AGN core shift measurements (Plavin+, 2019)J/ApJS/247/57 : Compact bright radio-loud AGNs. III. 43GHz (Cheng+, 2020)J/A+A/640/A69 : 3C 279 Event Horizon Telescope imaging (Kim+, 2020)J/ApJ/893/68 : RadioAstron. III. S5 0716+71 (Kravchenko+, 2020)J/A+A/641/A40 : S50836+710 Ground and Space VLBI images (Vega Garcia+, 2020)J/ApJ/923/67 : MOJAVE. XIX. Brightness temperatures of jets (Homan+, 2021)J/ApJS/260/12 : Jet kinematics of blazars at 43GHz (Weaver+, 2022)J/A+A/672/A130 : Blazar 3C 454.3 time variability (Chamani+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/952/34https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/952/34http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/952/34https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/952/34https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/952/34http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/952/34GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/952/34/table5Upper limits on the flux densities of M87 at 22GHz for space baselines to RadioAstron, in the order of increasing baseline lengthrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTobsstarting time of the scans, ISO8601 format UTCstime.epoch;time.startnullableCodeExperiment code for each observation (1)meta.id;obscharStationName of the ground station (2)meta.id;instr.obstycharTsol[559/1200] Solution interval used in the estimates of the S/Nstime.intervalintSN-obs[4/6.3] observed signal-noise ratiostat.snr;obsfloatSN-det[6.1/7] detection-threshold signal-noise ratiostat.snr;instr.sensitivityfloatBaseline[0.26/25.3] Baseline length in 10+6*{lambda}instr.baselinefloatPA[-177/179] baseline position angle, east of northdegpos.posAng;instr.baselinefloatFup[0.07/2.9] Upper limit on flux densityJyphot.flux.density;em.radio.12-30GHz;stat.maxfloat