Variation of M87 jet base revealed
by EAVN 2017-2019 campaign
Cui Yuzhu, Hada Kazuhiro, Honma Mareki, on behalfof EAVN AGN Science Working GroupContent• Background:- Previous work on M87 jet and black hole
- EAVN campaign in 2017, 2018 and 2019

• Results:- Light curve- Position angle- Connection with EHT scale- Time variation of position angle, opening angle and jet width• Discussion• Summary and future plan!2

BackgroundM87: the Best Laboratory To
Study the Jet and Black Hole• Highly collimated jetextended to kpc scale (5000ly) which is detectable atmulti-wavelength.

• Nearby radio galaxy: one ofthe closet AGN, D=16.7 Mpc(~53 million ly);?
Jet formation:
Why we didn’t
see the jetaround BH?

• Supermassive black hole?

inside: MBH=6.6 ×109M⊙?
!3

Position angle at mas scale:variable along 288∘

Stacked VLBA at 43 GHz

ti
Posi

gle
naon

+: more toward to northern

8°82~-: more toward to southern
Figure 20 in Walker+ 2018

• Position angle of M87 jet can be variable over time;• Comparison with simultaneous, low-frequency and multi-epoch VLBI
images (eg, EAVN/VLBA) is necessary.
!4

Background

East Asian VLBI NetworkTianmaKaVA𝛉 = 630 𝝁as

5100 km
Urumqi
KaVA+Tianma• Eight antenna joined at Q band;• Nine and more other antenna joined at K band.
!5𝛉 = 550 𝝁as

Background

EAVN campaigns during 2017-2019
Obs. Year Obs. Freq. Before April

April(EHT)

After April

Sum122 GHz

3195

2017

2143 GHz

6511222 GHz

23272018

1643 GHz

333922 GHz

52292019

SumSum21943 GHz62210227181156• EAVN total: 56 epochs (25@22 GHz, 31@43 GHz);• KaVA total: 22 epochs (11@22 GHz, 11@43 GHz)
!6PI: Hada

Uniqueness of our EAVN/KaVA M87
observations:• Multiple epochs fully cover EHT window:- Long-term variation (light curve, position angle, collimation,proper motion…)- connection between BH and jet• Simultaneous K and Q observation:- Reliable spectral index to trace the particle distribution!7

Q1: What was the status of M87
during EHT-2017/2018 window?

Results

M87: Falling into low statusfrom 2017 to 2019

✓ VLBA -> Q: 12 epochs(PI: Hada)✓ Genji -> Q: 19 epochs
K: 133 epochs(PI: Niinuma)• Starting from 2017, the flux of M87 keeps

decreasing; EAVN: (2.03±0.21) Jy, Genji: (1.83±0.36)
Jy, VLBA: (1.23±0.17) Jy, SMA: (1.6±0.23) Jy• It seems in 2019 the flux is recovering!9Q2: Can the long term position
angle variation be confirmed?

Results

Position angle of M87 jet(time variation)• We confirmed the transverse motion with 2017/2018/2019 EAVN (KaVA) data;• Around EHT period, the jet center has around 0.18 mas oﬀset which indicatesthe jet center in this method is toward to ~280 degree.
• The jet seems to reach the south-most!11point at the end of 2017

Q3: Why we didn’t see the jetemission surrounding the BH?

Results

Group our 2017 data into four groups tocompare the PA before/during/after EHT period
Stacked EAVN before EHT(January 11 - March 27)

Stacked EAVN during EHT(April 04 - 14)

Stacked EAVN after EHT(April 18- May 26)

VLBA (2017 May 05)

rotated -18∘

Results

Position angle of the M87 jet edges
and center at mas scale (2017)

Finally, by average theinformation at two sides,
the PA of the jet center at
mas scale is around(270~285)∘.
CloserOnlyoverall
The
EAVN data:
trend
confirmof tothethe
PAThenitthe
safe
to makeuse
core,
jetsignificant
center
towards
there
fornorthern
isisnoandsouthern
ofto
VLBA
on
05 to
more
horizontal
diﬀerencesides
isdatalikeofthis.
PAMayhappenedzoom
theregion
0.3
directionis diﬀerent
from intoJan.whichto May.
masto the core.
withcloser
the well-known
288∘PA.
0-1-2-3

Results

The non-detection of the jet at 𝛍as scale may be
due to the super-extended jet with a wide rangeof opening angle? (2017)
103

CenterEHT+ALMARadio Astron

GMVA+ALMABP jet10BZ jet
1Pitch angle of helical B field [deg.]

Northern

Radius: r [Rs]

(a)
102

90
80

Poloidal B
dominated

7060
50
4030

Toroidal B
dominated

2010(b)10 -1

110102

103

104

Distance from the black hole: z [Rs]Figure 3. Synergy of multi-wavelength imaging of M 87 jet: (a) Collimation profile of the M 87 jet. Sy
denote the measured jet radius (r) along the jet axis (z); the thick grey area shows the theoretical model ofergosphere-driven force-free jet (Narayan et al. 2007) with various BH spins. (b) Expected B-field pitch angle pvs. BH distance for di↵erent BH spins (solid lines). A transition from a poloidal-dominated B-field to a todominated B-field is expected near the Alfvén surface (black squares), where the pitch ' 45 (red line) is exp(c,d) GRMHD simulation images of the M 87 jet at 1.3 mm and 3 mm (Mościbrodzka et al. 2016).

Southern

1. The jet PA at 𝛍as scale istimates that rely on stellar dispersion (Gebhardt et al. 2011) and gas dynamics (Walsh et al. 2013
consistentwiththat
ataddition, the exact determinationof the BH parameters
will also
allow us tocheckmas
for deviations
the canonical Kerr solution (e.g., Kerr with scalar hair: Cunha et al. 2016; Einstein-dilaton-G
especiallyat theBonnet: Cunha et scale,al. 2017) and potentiallyeven constrain quantum
fluctuations at the ho(Giddings & Psaltis 2016).
regioncloseObjective #2:innermost
Resolve Jet Formation
Near a Black
Hole toIdentifying the processes that govern the formation, acceleration and collimation of powerfultivistic jets is a half-century-longgoal in the BH astrophysics. GRMHD simulations have dramat
the core
improved our theoretical understanding of BH ergosphere-driven jets (e.g., McKinney 2006),
our recent extensive VLBI imaging of M 87 at long wavelengths ( 7 mm) has revealed that th
2. Further
exhibits a parabolic
collimation shape atjoint
large scalesmm/cm-VLBI(z / r : Asada & Nakamura 2012; Haal. 2013; see Fig. 3(a)). With Cycle 5 EHT observations, we seek definitive evidence to validat
BH-driven jet paradigm
by addressing three key unresolved
challenges:
monitoringin thefollowing
Paper VI,
Jet Collimation Slope Near the BH: While our previous M 87 studies based on cm-VLBI im
a parabolic jetcampaign
profile beyond z ⇠ 100 R ,will
the collimationof thesome
innermost region b
Table 5 show
fill slope
the100 R is still poorly determined (Nakamura & Asada 2013; Hada et al. 2013) due to the lasufficient N-S (= transverse to the jet) angular resolution (Fig. 3(a)). Determining this inner
betweenscaleandcollimation slope is gap
crucial to conclude
whether the jet 𝛍as
is ultimately
anchored in theBH ergos(BZ jet; Blandford & Znajek 1977) or the inner part of accretion disk (BP jet; Blandford & P1982). A joint image analysis of quasi-simultaneous EHT+ALMA 1.3 mm data (sensitive to tmas scale and better solve
emission at z . 10 R ), GMVA+ALMA 3 mm data, and RadioAstron 13 mm data (which aresensitive to the outer jet), is crucial to uniquely determine the jet collimation slope over thethiskey
two orders of magnitude
in distancenear question
the BH. Because neither of the latter two observation
1.7sssavailable for our Cycle 4 observations, they are an important new opportunity for Cycle 5.
Topology of B-field: In the MHD jet scenario, the jet is initially accelerated by magneto-centr
force, up to the Alfvén surface (Fig 3(b)). Thereafter, the jet acceleration is ascribed to magpressure and/or magnetic tension forces (e.g., Meier 2013). Recent GRMHD analyses have s

Q4: What is the long-term variationof the jet width, opening angle andS-N brightness ratio?

Results

Time variation of PA, OA Jet width,and S-N BR
Fig1: Position angle

Fig2: Opening angle

Fig3: Jet full widthFig4: S-N brightness ratio!17

Discussion

Well confined jet shape no matter
how jet direction changes?
z

PI: J. Kim+, GMVA+ALMA proposal (Cy. 7)• Well confined jet shape which is with fixed opening

angle and jet width at certain distance to the BH, thejet axis direction is changing with the time

FigureGRMHD+GRRT images and simulated GMVA(+ALMA) observations of the1.
2-D2:oscillation

the legend for references). Top and bottom : jet formation with high and low magnetic
2.
oscillation:is asimulations,
5 degree error
bar ofGMVA+ALMA
openingleft 3-D
to right: images therefrom thesynthetic
observations, aangle
in the projected plane, that means the possible
without
ALMA.

precession angle is within 11 degree

the structure of the onset of the jet, (iii) establish firm evidence for the mlaunching in M 87 based on polarization measurement.
3 Immediate Objectives :!18

Discussion

The brightness distribution variationis connected with the jet PA change?

imilre!
yrnai!
yrnamreli

PP!19

Summary and future plan
1. Data analysis:• Jet collimation profile;• Jet position angle (north/south/average);• S-N brightness ratio variation;• Jet kinematics / motion;• Spectra profile
2. Theoretical model
3. New proposal of EAVN-EHT
campaign in 2020A: submitted

12 sessions, 7 h/session!20