sub-mm VLBI for resolving
super-massive black hole
Mareki Honma
VERA / Mizusawa VLBI observatory,
NAOJ
Target : touching the event horizons of BHs
•AGN core is most-likely a
super-massive black hole.
•Yet, there is no confirmation
of existence of event horizon
Fukue et al 1989
Direct detection of BH shadow is an ultimate
confirmation of existence of BH. (or negative results
may indicate an existence of naked singularity !?)
•New breakthrough for experimental BH physics!?
BH size
source
MBH/Msun
Distance
Angular
radius
Sgr A*
4 x 10^6
8 kpc
10μas
M87
3 ~ 6 x 10^9
15 Mpc
4 ~ 7μas
M104
1 x 10^9
10 Mpc
2μas
Cen A
5 x 10^7
4 Mpc
0.25μas
Shadow diameter : 1~5 times Schwartshild radius
For imaging shadow, ~ 10μas resolution is required
Angular resolution of telescopes
• Wavelength – angular resolution diagram
cm wave
mm wave
IR
optical
Resolution in mas
AKARI
1 arcsec
Connected
array
VLBI
VERA
SUBARU
ALMA
HST
Single dish
1 mas
VLBA
VSOP-2
λ
Submm VLBI
Sgr A* BH size
Doeleman+(2008)
• 230GHz VLBI with JCMT – SMTO – CARMA
ARO/SMT－CARMA(600km)
ARO/SMT－JCMT
Non-imaging analysis (traditional UV distance plot)
･ 37±(16,10) Intrinsic diameter of Sgr A*
･ Non detection on the JCMT-CARMA（3075 km）
Sub-mm VLBI of Sgr A*
1995 Mar
…
2006 Mar
2007 Mar
2009 Mar
2010 Mar
2011 Mar
IRAM30m-PdB
Krichbaum+ (1998)
Hawaii-SMTO-CARMA
failed
JCMT-SMTO-CARMA
Doeleman+(2008)
but IRAM/PdB failed
Hawaii-SMTO-CARMA
SMA phase-up
Fish+(2011)
Hawaii-SMTO-ASTE
Hawaii-SMTO-CARMA-APEX-IRAM
but not fringes from Chile and Europe …
Sub-mm VLBI with ASTE (2010)
Chilean station will be a key for Sgr A* observations
good site & longest baselines
CARMA
SMTO
JCMT
ASTE
UV coverage for Sgr A*
（red: UV with ASTE）
fringe spacing ~30μas
Sub-mm VLBI in 2011 Mar/Apr
International campaign from Mar. 28 to Apr. 5
CARMA
SMTO
(Pico Veleta)
Hawaii
(APEX)
Planned Array for April 2011 obs.
US array (Hawaii-CARMA-SMTO) is the core
European stations may join (APEX / IRAM 30m)
Steps toward future
• Re-trial with Chilean stations (ASTE/APEX) ?
• Green land (ASIAA) : ALMA prototype move in 2013 ?
• LMT : VLBI capability ?
• ALMA phase-up is the key (both sensitivity & imaging capability)
Proposal to NSF MRI in 2011
Haystack/ NRAO/ MPI/ NAOJ/ ASIAA etc.
Highly-ranked by NSF review and
will be funded this year.
observation from ~2015 (?)
• Large (sub-)mm telescope will be very
useful.
ALMA phase-up plan
• Phased-sum in
baseline correlator
data transfer to OSF
& recording there
• Japan’s part :
optical-fiber transmission
between ALMA – OSF
Correlator
(sum-up)
Optical fiber
(8 x 8Gbps)
OSF(@2900m)
Science cases
•
•
•
•
BH shadows : Sgr A* & M87
Jet monitor: launch/accelaration mechanism
Detailed structure of accretion disk
Time variation (Sgr A*: 15min, M87 : a few days)
of structure near BH
• Rotation of hot spot/disk patch > test of General
Relativity in strong gravity field.
M87 at 43G
New laboratory for “Black Hole Physics”
+ non-BH sciences
SFR/AGB masers, astrometry
(LMC/SMC, for instance)
BH simulation
Gammie & Noble
Discriminating models for M87
• Simple simulations how ALMA works out
Gaussian with 13.0-μasRing between 15.0 - 25.5μas
radius shadow
Simulated and observed
visibilities vs. UV distance
Chile
baselines
Gaussian with 38μas FWHM
Disk with 30μas radius
Chile
baselines
γ-ray emitting AGNs
• Example : 3C84, radio jet detection (VERA) after
γ-ray flare (Fermi)
VLBI map (2 x 2 pc), at 22 GHz
Nagai+(2010)
Radio light curve
cm + (sub-)mm VLBI will lead
comprehensive understanding
(higher resolution &
lower optical depth …)
SSC model
for Mrk 501
(Kino+2001)
γ-ray mitting
region:<1000 AU
Science cases around 2020
Basic assumption : BH shadow itself is already seen
•Jet monitor: launch/accelaration mechanism
•Detailed structure of accretion disk
M87 at 43G
•Time variation (Sgr A*: 15min, M87 : a few days)
of structure near BH
•Rotation of hot spot/disk patch > test of General
Relativity in strong gravity field.
New laboratory for “Black Hole Physics”
BH simulation
Gammie & Noble
role of new large telescope in Chile in VLBI
• Even if ALMA phase-up goes, machine time should be very
limited (machine time is very important, e.g., for monitor).
50m(?) in Chile will expand possibility of doing VLBI.
• Combination of 50m in Chile and phase-up ALMA (50 of 12m) equivalent to 98-m dish !!
• 50m-ALMA for short baseline obs. (30 km – 100 km?)
Providing new “longest” baseline for ALMA
> additional science cases, such as resolving
nearby giant stars
Summary
• Sub-mm VLBI will open up wonderful science
cases with ultra-high resolution:
resolving BH shadows, Jet launching / gammaray-jet connection and more…
• Large (sub-)mm telescope will be useful to expand
science cases with sub-mm VLBI (e.g., monitor
etc.)