SummaryofKaVA/EAVNobservationsofM87andSgrA*in2014-2018

M.Kino(NAOJ/KUTE)&BWSohn(KASI)onbehalfofEAVNAGNScienceWG

2019/Sep EAVNWorkshop2019Sep,atIbarakiUniv

Grandchallenge#1:solvingjetformationmechanism

EHTtalksG.Bower(ASIAA)F.Tazaki(NAOJ)

(c)EAVNCollaboration

(c)EHTC

TotestB-drivenjetmodel,wemeasure/constrainbasicquantitiesof

1.  velocityfield2. B-field3.  flowgeometry

BZprocessatwork?

v-field,B-field,andflowgeometryofM87Park+2019submittedRoetal.inprepCuietal.inprep

EAVNWorkshop2019

Longstandingproblem:“IstheM87jetfastorslowinthecollimationzone?”

Asada+(2014)

fastorslow?

Keytoresolvetheproblemishighcadencemonitoring,

whichcanavoidmisidentificationsofthemultiplejetcomponents!

TheKaVAhigh-cadence(bi-weekly)monitoringin2016revealstheprofileofM87’sjetvelocityfield.

22GHz

Park+submitted

43GHz

1.Velocitystratification!2.Discrepancybtw.observationandGRMHD?!

Park+submitted

ConstrainingB-fieldinM87at22/43GHz(2015-2016data)

H.RowillpresentnewconstraintsonB-fieldpropertiesviaradialprofileofthespectralindex.Staytuned!

Ro+inprep

Flowgeometryatthejetbase

l Unfortunately,EHTcouldnotdetectthejetemissioninEHT2017.

whichdirection?jetopeningangle?

EHTC’sestimateofPositionAngle(PA)ofForwardJet(FJ)viamatchingGRMHDsnapshottothephotonring

EHTC+2019,ApJL

EAVNmeasuretherealjetPAin2017AprilCui+inprep

Southernlimb

Northernlimb

FromtheEAVNdata,wefindthat(1)widejet-openingangle,and(2)EHTCestimatesofPA_FJreasonablyagreewithEAVNjet.

Cui+inprepPo

sition

Ang

le[d

egree]

RelativeRA[mas]

320

230

Northernlimb

Southernlimb

ProbingrealvicinityofSMBHCho+inprep(Zhao+inprep)

EAVNWorkshop2019

Grandchallenge#2:UnveilingaccretionflowontoSMBH

VLAimage(c)Lo

minispiralatGal.Center

(VLA)

1pc

SgrA*(EAVN)

100Rs

Wearealmostthere.However,thereisoneseriousissue.

Longstandingproblem:“ObservedradioimagesofSgrA*isdominatedbyinterstellarscattering.

So,aninferenceofSgrA*imageissensitivetoanassumedscatteringmodel.”

(c)Akiyama

angularbroadening

non-Gaussian&substructure

Johnson+2018

KaVA7mmdata(2014Nov)showsnon-Gaussiananditsignificantlyconstrainsscatteringkernel.

Johnson+2018

Thescatteringparameters(αandr_in)arefinallyconstrainedverytightly!

So,usingtheseparametersinJohnson+2018wecanremovetheeffectofthescatteringandthuswecanderiveintrinsicsizeofSgrA*in2017.

EAVNobservationofSgrA*on2017April3rd@22GHz

Cho+inprep

IntrinsicsizeofSgrA*!

Fromthis,wecanpotentiallyconstrainongeometryofSgrA*andelectrondistributioninit.

Cho+inprep

ThearrayisinatransitionphasefromKaVAtoEAVN.(i)TransversemotionoftheM87jet(ii)OriginofflaresinSgrA*

EAVNworkshop2019

TimeallocatedforinitialphaseofEAVNLPin2019Sep–2020Jan

IljeCHOandGuangyaoZHAO

HyunwookRO

EAVNLPofinvestigatingthetransversemotioninM87

Thetimescaleofapossibleoscillationisoneyearscale.Hence,longtermmonitoringat22GHzisessentialtocharacterizeitsproperties.Wecanstudyoninstabilitiesinthejet.

RA[mas]

Declin

ation[m

as]

Ro+inprep

SignificantIRflareactivityin2019Doetal.(2019)

observedflareflux(mJy)freq

uencydistrib

uXon

TheelevatedIRflareactivityencouragesEAVNLPmonitoringofSgrA*.

Doetal.(2019)saysl  “Thedistributionoffluxvariationsobservedthis

yearissignificantlydifferentthanthehistoricaldistribution.”

l  “PotentialphysicaloriginsofSgrA*’sunprecedentedbrightnessmaybefromchangesintheaccretion-flowasaresultofthestarS0-2‘sclosestpassagetotheblackholein2018orfromadelayedreactiontotheapproachofthedustyobjectG2in2014.”

SummaryofEAVNAGNScienceWGactivities

l  Paperdraftingw/KaVALargeProgramdatain2014-2018ü  Park+2019submitted(M87velocityfieldin2016)ü  Ro+inprep(M87magneticfieldin204-2016)ü  Cui+inprep(M87jetPAin2017-2018)ü  Cho+inprep(SgrA*intrinsicsizein2017April)ü  Zhao+inprep(SgrA*intrinsicsizein2013-2016)

l  ConductinginitialphaseEAVNLPin2019Bü  TransverseoscillationoftheM87jetü  OriginofsignificantflaresinSgrA*

l  Development/upgradeofEAVNü  KaVA/EAVNpolarimetry(BWSohn+,K.Hada+,J.Park)ü  KaVA/EAVNphase-ref(J.Oh+)ü  EATINGVLBI(M.Giroletti+)ü  EAVN-high(K.Asada+)