NAOJ Achievements and Future
Planning Symposium 2019
December 12-13, 2019

VLBI Community:
Current assessment andexpectations for the future
FUJISAWA Kenta(Yamaguchi University)

VERA and JVN

VERA – a dedicated Japanese VLBI for astrometry• 4 20m telescopes• 2300 km, 22, 43 GHz• Dual-beam for highprecision astrometry• ~10mas accuracy• Simultaneous observation ofclose pair: target andreference source• Systematic errors including
atmospheric fluctuation arecancelled out
VERA’s high precision astrometry is mainly used for Galactic dynamics. Annual
parallax and proper motions of water maser (22 GHz) sources are measured,and the gas dynamics of the galactic plane is studied.

Achievements of VERA
Measurement of distance and 3D motion by annual
parallax and proper motion

Orion nebula
Orion Molecular Cloud

Observed motion of a water maserin Orion KLHirota+(2007)

Distance 480 pc

Galaxy rotation

VLBA/VERA/EVN

Galactic constants
Honma+ (2012)

Update52 SFRs

144 SFRs

R0 = 8.05±0.45 kpc

R0 = 8.16±0.26 kpc

Θ0 = 238±14 km/s

Θ0 = 237±8 km/s

Ω0 = 29.57±0.78 km/s/kpcΩ0 = 28.99±0.39 km/s/kpc(U, V, W) = (11.10, 12.24, 7.25) km/s (Schorich, Binney, Dehnen 2012) assumed

Rotation curve from 144 SFRs

Now GAIA is producing a huge amount of astrometric data, and VERA is shifting
the focus to imaging VLBI observation with EAVN collaborationVLBI imaging observation by VERA
Jet-clump interaction in the heart of 3C84

VERA/KaVA biweekly jet monitor

Nucleus

C3Size~0.15pc

C3 strong brightening along with flip

Kino+2018, Hiura+2018, Hirano in prep.

Japanese VLBI Network (JVN)

Imaging VLBI network including VERA and University’s telescopes• Collaboration• NAOJ (VERA)• Hokkaido, Ibaraki, Tsukuba, Gifu,Osaka-Pref, Yamaguchi,
Kagoshima universities• JAXA, NICT, GSI• Specifications• 13 telescopes (11m ~ 64m)
• 6~7 active telescopes• Baseline 50 - 2500 km• Frequency 6.7/8/22 GHz• Operation••

500hr/yr
100 observations/yr

Internal Motions of 6.7 GHz methanol maser
motions of maser spots in Cep A (Sugiyama et al. 2014)

6.7 GHz Methanol Maser distribution in High-mass star forming regionCepheus A HW2(Sugiyama et al. 2008)

Internal Motions of 6.7 GHz methanol maser
motions of maser spots in Cep A (Sugiyama et al. 2014)

Rotaion：1.2 km/s, Infall：2.4 km/s. The gas disk is rotating and infalling.

A systematic study of internal motion

for 36 sources by JVN + Shanghai (a precursor observation of EAVN)Time domain VLBI astronomy
by JVN (A-project of NAOJ, since 2019)• Advantage of university’s telescope: Long available time,flexible operation

Monitoring/Detecting ariable sources with amountof observing time• Three main science targets of JVN• Periodic methanol maser• Extremely Compact HII region• Gamma-ray objects• ・・・and various transient/variable targets

KaVA(KVN+VERA)KVN – multi-frequency mm VLBI
• 3 21m telescopes in South Korea• Baseline 500 km• 22, 43, 86, 129 GHz• Simultaneous observation at four
frequencies with quasi-optic system• Science• SiO/H2O/CH3OH Masers• Investigating spatial structures anddynamical effects from SiO to 22 GHz H2Omaser regions (atmosphere to circumstellarenvelope) according to stellar pulsation
through simultaneous monitoringobservations.

• AGN / polarization

The key features of KVN are (1) capability of multi-frequency simultaneousobservation, and (2) regular observation at mm wavelength. Imaging capability isgreatly enhanced by co-observation with VERA.

KaVA – Combined array of KVN and VERA• KaVA• KVN and VERA Array• 22, 43 GHz• Started in 2010
• Open use since 2014

• Good imaging capability• Almost uniform array• 7 sites, 21 baselines• Baseline 300 - 2300 km• The core of EAVNKaVA (KVN and VERA Array)• KaVA: KVN and VERA Array, 7station 21 baselines• Open-use started since 2014
• KaVA Large Project starts in 2015

M87 jet with VERA

KaVA

Demonstration of KaVA’s capability: Niinuma et al. (2014)

M87 jet motion monitorwith KaVA

M87 with HST
Hada et al. (2016)

Unveil jet acceleration zone with KaVA
Hada+2017 PASJ; Park+ in prep; Cui+ in prep

KaVA/EAVN• Question of M87 jet acceleration : where is the jet accelerated?
• Discovery of fast (~2-3c) motions in inner jet!
• Gradual acceleration between 500Rs – 20000Rs

“Heat-wave” propagation detected by KaVABurns et al. (2019) accepted to nature astronomy

Rapidly expanding maser emission region. Heat-wave generated in the central star is
propagating through the maser emission region.

EAVN(CVN+KVN+VERA/JVN+α)The East Asia VLBI Network (EAVN)• Situation in and around East Asia
• Regular operation of VLBI facilities in each EA country(VERA/JVN (JP); KVN (KR); CVN (CN))• A small task force, ‘the EAVN Tiger Team’ wasorganized on June 2013 to handle various issues
related to EAVN
• To promote VLBI test observations• To proceed data reduction of test observations• To clarify the problems for future regular operation andopen-use observations with EAVN

To construct a VLBI network in East Asia

The East Asian VLBI Network (EAVN)
An, Sohn, Imai 2018

• VERA/JVN (Japan), KVN (Korea), CVN (China)• Collaborative effort to form a large VLBI network in East Asia

M87
KaVA +TM +UR +HT
2017 March 18 (22GHz)

More results on EAVN-M87-2017 (22/43, spectra, kinematics, jet base)

EAVN MoU @ EAVN WS Sep/2018, Pyeongchang

EAVN open-use has just started
Urumqi26

NRO45
KaVA

KaVA
(KVN+VERA)

UrumqiTianmaTianma65• First EAVN open-use observations starting from Oct/2018• Available stations: 10 (KaVA, Tianma, Nobeyama, Urumqi)• Bands: 22GHz (13mm), 43GHz (7mm)• Angular resolution: 0.5 mas• Good sensitivity at 22/43GHz

Nobeyama

Array sensitivity of EAVN
2Gbps (512MHz BW), 1hr integration

43GHz
VLBA: 10EVN: Ef, On, Ys, Nt
EAVN: KaVA, TM, NY
22GHz
VLBA: 10EVN: Ef, Mc, On, Tr, Nt, Ur,Ys, Hh, Sv, Zc, Bd
EAVN: KaVA, TM, UR, NY,HT, TH, KS
6.7GHz
VLBA: 10
EVN: Ef, Mc, On, Tr, W1, Nt,Ys, Hh, Ir
EAVN: VERA, KUS, TM, KM,HT, TK, KS, YM, US• EAVN: “high-sensitivity” + “regular monitoring capability” at 6.7-43GHz• Complementary to other VLBI facilities

An, Sohn, Imai 2018

UV coverage of major VLBI arrays
Target: M87, Frequency: 22 GHz

An, Sohn, Imai 2018

EAVN (+ Italy) AGN Campaign• Main purpose• To obtain scientific results with EAVN
• To conduct VLBI monitoring quasi-simultaneously with EHT +ALMA campaign• (To evaluate system performance of EAVN)• (To check up on the array operation and availability ofKEY/VEX files at each station)• Brief summary of the Campaign• Main target: Sgr A* (43 GHz), M87 (22 and 43 GHz)
• Total observing time: 186 hours/18 epochs (83 hours/9epochs at 22 GHz; 103 hours/12 epochs at 43 GHz)• cf. EAVN campaign in 2017: 40 hours/5 epochs at 22 GHz; 100 hours/12epochs at 43 GHz• Number of participating telescopes: 14 (Italy: 2, China: 2,Korea: 3, Japan: 7)

Correlation and data reduction ongoing

M87
KaVA +TM +UR +HT
2017 March 18 (22GHz)

More results on EAVN-M87-2017 (22/43, spectra, kinematics, jet base)Intensive monitoring of M87/SgrA
EAVN

EHT

• EHT will see the first horizon-scale images of SMBHs (SgrA/M87)• Centimeter-VLBI plays key roles in many aspects:• Connect the horizon scales to large-scales (accretion flows, jet collimation)• Subsequent evolution/propagation of ejected jet (jet acceleration, shock)• Spectral information of synchrotron plasma (B-field, Ue/UB)• Scattering screen towards SgrA
• EAVN is a suitable facility to complement EHT

SgrA*Zhao+ in prep

KaVA+Tianma@43GHz• EAVN: Very dense uv-coverage for SgrA
• First 300Mλ detection at 43GHz (Tianma - Ogasawara)• Non-gaussianity?
• Contemporaneous 22GHz data => scattering properties• Millimeter-regime core-shift with KVN

More results are coming from EA-VLBI
SgrA* (Zhao+; Cho+; Johnson+2018)

High-z quasars (Zhang+2018; Furuya+)NLSy1 (Wajima+)

And more!

Future expansion of EAVN
• More stations• E-KVN• QTT 110m
• Thai 40m• Malaysia• Indonesia• EAVN with FAST (<3GHz)• Sensitivity comparable to
SKA1, but 30 times higher
angular resolution• “World Array” with
EAVN+EVN+VLBA

Expanding observing frequency to Lower and Higher

EA stations with 1-2GHz receivers
QTT 110m (2022~?)
Usuda 64m

Nanshan 26m
FAST 500m

Tianma 65m
Kashima 34m
Sheshan 25m

TNRT 40m (2020~)

Ultra-high-sensitivity VLBI in EA
To collaborate with SKA

Expanding observing frequency to Lower and Higher

NRO 45m Triple band observation• System change/upgrade• Kunming 40 m: 6.7 GHz receiver available• Nanshan 26 m: 43 GHz cooled receiver• Nobeyama 45 m: New quasi-optics at 22/43/(86) GHz
simultaneous reception (HINOTORI Project)• VERA:• Dual polarization system: receiver development ongoing• Installation of 22/43 GHz simultaneous reception system at allstations• 2 Gbps operation• KVN: operational (up to 16 Gbps)• VERA: test observations ongoingBlack hole Shadow
EHT observations in 2017

The shadow of M87’s super-massive
black hole

• 5 nights on April 5-11, 2017
• 8 stations at 6 sites participated• Maximum baseline ~ 10000 km• Wavelength ~ 1.3 mm• Nominal beam ~ 25 uas

EHT Collaboration

Ring-size：0.01 ly (4 light day)
Mass: 6.5 x109 Solar mass

A new station to EHT
Balloon-borne VLBI ?
• EHT collaborations seriously consider
the future array extension with spacestation• Better images, some more sources
with shadow• See Astro2020 paper (will be opened)

Balloon VLBI experiment by Doi et a.

Future Plan of VLBI astronomy in Japan• Under discussion in various layers• VLBI consortium• Working groups (in Mizusawa, VLBI consortium, JVN)
• Mizusawa VLBI User’s Meeting• VLBI Science Advisory committee in NAOJ

• Short term

• From VERA to EAVN, JVN• Just started good collaboration. We plan to keep and expand
the activity under the international collaboration.

• Long term

• Large international project (SKA, ngVLA, …), New Satellite
VLBI, New telescope led by Universities

New VLBI technologies developed by NAOJ
• High speed sampler, Digital filter• Optical fiber data transmission• High precision phase-referencing / astrometry• (Space-VLBI, 2-beam receiver, …)
OCTAVE system
VSI based VLBI terminal,32 Gbps (max) recording capacity
World compatibility, suitable to the East-Asian Correlator

10 GbE Switch

Optical fibertransmission system

Disk pack

OCTADISKNAOJ’s expected role in VLBI
• A research base is expected to be in NAOJ
• Cutting edge development research is expected to belead/backuped by NAOJ
• University’s research strongly depends on personality ofeach researcher (unstable). NAOJ is the stable core of VLBI.

• A key: Cooperation of Nobeyama and Mizusawa

Implication of EAVN
• Background• Simple ‘Expansion’ model is difficult in Japan now• Demographics, Social security expenses, Economical recession…

• Still, the achievements of Japanese astronomical society isrespected by communities of east Asian countries• Construction of new VLBI telescopes in east Asia
• ‘Collaboration’ strengthen the performance of VLBIEAVN construction• Let the owls of Minerva fly as messengers• To construct a new network of knowledge and research