Closing Remarks

6.7GHz8GHz

22GHz43GHz(ImageCredit:Reto Stöckli,NASAEarthObservatory)

Ogasawara20mIriki 20m

Ishigakijima 20m

Mizusawa 20m

Kashima34m

Takahagi 32m

Hitachi32m

Usuda 64mGifu11m

Yamaguchi32m

Nobeyama 45m

Sheshan 25mKunming40m

Tianma 65m

Nanshan 26m

Miyun 50m Ulsan21mTamna 21m Yonsei 21mSejong 22m

VERA

KVN

JVN

CVN

Kenji TOMA (Tohoku U)

BH Jet

Disk

Wind (or Accretion?)

EHT 2017 & next- Jet driving mechanismLBZ = LBZ(WH, BH)

- BH spin, gravity theories- Polarization/time domain- GLT (350 GHz)

& more stations- Space VLBI- Sims: Rhigh, density floor

Bondi radius?

EAVN & next- Jet kinematics- Width profiles- Acceleration mechanism- Core shift:

B field strength- Energetics

Tazaki, Akiyama, Mizuno, Kawashima

Park, Nakahara, Jung, Niinuma, Nakamura, Kino, Tanaka, Ohmura

Radio Galaxies- LLAGN, NLSy1- Two key “3”s- Population

Blazars- EHT view, kinematics- Polarization Kim, Shin,

K-W Lee

Plasma microphysics- Te/Tp- Non-thermal p / neutrinos- Jet MHD breakdown

Kawazura, Kimura, Kisaka

Gamma-rays/X-rays- Jet, disk, magnetosphere?- Fe lines- X-ray interferometer

Mazin, Chamani, Hayashida

Limb-brightening

Ohsuga, Hada, K Lee

One point• Number of faster blobs looks smaller

Observer

t

r

Light

Blobs

Observer

t

r

Light

Faster blobs

9

�25�20�15�10�50RA (mas)

�4

�2

0

2

4

Dec

(mas

)

WISE - 0.2 mas

KaVA, 22 GHz

�6�4�202RA (mas)

�2

�1

0

1

2

WISE - 0.12 mas

KaVA, 43 GHz

Fig. 6.— Stacked maps of the CLEAN images at 22 (left) and 43 GHz (right) rotated clockwise by 18� with respect to the map center.Contours start at 0.8 mJy per beam and increase by factors of

p2. The displacements of several SSPs between adjacent epochs detected

at the finest SWD scales are shown with the arrows (see Section 4.3 for more details).

We assumed the minimum scale to be ⇡ 1/5 of thebeam size and maximum scale to be about one beamsize. We applied the SWD on three spatial scales of 0.2(0.12), 0.4 (0.24) and 0.8 (0.48) mas and amended themwith the IWD on scales of 0.3 (0.18), 0.6 (0.36), and 1.2(0.72) mas at 22 (43) GHz. We identify SSPs in adja-cent epochs by using the MCC method with a tolerancefactor of 1.5 and a correlation threshold of 0.7. In theMCC analysis, we search for velocity vectors with sym-metric search windows of [�31, +31] mas/yr and [�18,+18] mas/yr in a longitudinal direction relative to thejet axis at 22 and 43 GHz, respectively. We used searchwindows of [�10, +10] mas/yr and [�5, +5] mas/yr in atransverse direction at 22 and 43 GHz, respectively. Thisconstraint is based on the maximum SWD/IWD scalesand the typical time separation between adjacent epochs.We use velocity vectors of the SSPs matched in at leastfour successive epochs for our further analysis. We ob-tained the apparent speeds by fitting linear functions totheir separation from the core with time.

We note that we used symmetric velocity searchwindows, while previous studies using WISE analysisadopted asymmetric search windows in a longitudinal di-rection (Mertens et al. 2016; Boccardi et al. 2019). Thereason for using asymmetric windows in those studies isbased on our prior knowledge that fast inward motionsare not physically realistic. However, at least for thepresent study, we found that using an asymmetric ve-locity search window can lead to biased results towardsdetecting faster speeds. In Appendix B, we perform sev-eral tests by using one hundred randomly shu✏ed im-ages of the VLBA 1.7 GHz data presented in Section 5,which provide us with a number of detected WISE vec-tors and good statistics. We observed a systematic accel-eration pattern with distance even for the shu✏ed dataset when we use an asymmetric velocity search window.This indicates that an artificial acceleration feature canbe observed in the real data as well due to the asym-metric search window. Thus, we used symmetric searchwindows to ensure that the observed speeds and jet ac-celeration result from real jet motions.

Also, we found that the statistical behaviors of thereal data and the shu✏ed data become significantly dif-ferent when using the SSPs matched in more than four orfive successive epochs (Appendix B). This result implies

that false detection due to a chance alignment may besuppressed in our KaVA WISE analysis that uses SSPsmatched in more than four successive epochs. However,a number of jet motions are still detected in the ran-dom data set when a length-chain of four or five succes-sive epochs is used. This suggests that one needs to usea longer length-chain such as seven or eight successiveepochs, if possible, to obtain robust results. Neverthe-less, we had only eight epochs in total for the KaVA im-ages and using such a long length-chain was not available.Instead, we used a larger correlation threshold (0.7) com-pared to the previous studies (0.6, Mertens et al. 2016;Boccardi et al. 2019) for our KaVA data to reduce theprobability of false detection.

We found that our WISE results show a significantdependence on di↵erent SWD/IWD scales at both fre-quencies (see Appendix A for more details). This be-havior was not clearly observed in the previous WISEanalysis of the VLBA data at 43 GHz (Mertens et al.2016), nor in our WISE analysis of the VLBA data at 1.7GHz (Section 5). The scale dependence is likely due tothe limited angular resolution of our KaVA observationsbecause the sampling interval of our data (⇡ 2 weeks)is short enough compared to the previous studies (& 3weeks, Mertens et al. 2016; Boccardi et al. 2019). Basedon this argument, we selected the results of the finestscales, which provides the highest e↵ective spatial reso-lution among di↵erent scales. Figure 6 shows the WISEvectors detected at the finest scales. We found manyvectors having a wide range of speed from stationarymotions to fast outward motions up to ⇡ 2c.

4.4. Jet Apparent Speeds and Comparison with Other

Studies

We show the mean radial distances from the coreand the observed radial speeds of the jet componentsobtained by the three methods in Table 2. We presentthe apparent jet speeds in the left panel of Figure 7.The apparent speeds, in general, increase from ⇡ 0.3c ata distance ⇡ 0.5 mas to ⇡ 2.7c at ⇡ 20 mas. However,there is non-negligible dispersion in the speeds at a givendistance. Many of the slower speeds come from the WISEanalysis. On the contrary, the speeds of the fast outwardWISE vectors are in good agreement with the modelfitresults. This may imply that the WISE analysis can

Park, Hada, Kino et al. 2019

See Komissarov & Falle 1997

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Many thanks for your participations, contributions & discussions!Let us keep in touch & make our community more active.

We will prepare a next BH/jet workshop.