ミリ波サブミリ波VLBIの現状と将来

国立天文台 水沢VLBI観測所
本間 希樹

Contents• EHT	  and	  (sub)mm	  VLBI	  for	  imaging	  black	  hole	  shadow• Our	  recent	  activity	  • Future	  Prospect1.	  EHT	   and	   mm	  VLBI	  for	   imaging	  black	  hole	   shadow

Resolving the event horizons of BHs•AGN core is most-likely asuper-massive black hole.
•Yet, there is no confirmationof existence of event horizon

Fukue et al 1989

Direct detection of BH shadow is an ultimate confirmation ofexistence of BH. (or negative results may indicate an existenceof naked singularity !?)•New breakthrough for experimental BH physics!?

BH	  size
sourceMBH/MsunDistance

Angularradius

Sgr A*

4  x  10^68  kpc

10μas

M87

6  x  10^915  Mpc

7μas

M104

1  x  10^910  Mpc

2μas

Cen  A

5  x  10^74  Mpc

0.25μas

Shadow diameter : 1~5 times Schwartshild radius
For imaging shadow, ~ 10µas resolution is requiredAngular	   resolution	  of	  telescopes• angular	  resolution:	  Θ～λ	  /	  D
cm wavemm wave

IR

opticalResolution in mas

AKARI
1 arcsec

Connectedarray

VLBI
VERASUBARU

ALMAHST

Single dish
1 mas

VLBA
Submm VLBIλSgr  A*  BH   size

Sgr A*	  case
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*• As compact as ~ 4 R_s

M87	  jet-­‐base	  detection

VLBA	  @	  7mm

Science	  338,	  355	  (2012)シュバルツシルト半径の5.5倍の構造を検出

EHT	  (Event	  Horizon	  Telescope)(sub)mm	  VLBI	  array	  to	  resolve	  BH	  images
Green land
CARMASMTO
Pico Veleta

HawaiiLMT

ALMA (NRAO/ESO/NAOJ)
ALMASPTAPP	  (ALMA	  Phase-­‐up	  Project)International	  collaboration	  for	  ALMA	  up-­‐grade• ALMA	  board	  acceptance	  in	  2012
• APP	  CDR	  (Critical	  Design	  Review)	  held	  in	  2013
• APP	  test	  observations	  in	  2014/15	  • Open	  use	  in	  2016	  ?	  (Cycle-­‐4	  ?)ALMA VLBI era is coming soon
We need to get prepared for the era for sub-mm VLBI with ALMAAPP	  contribution	  from	  Japan• contribution	  to	  APP:	  optical	  fiber	  link	  (AOS-­‐OSF)
data	  transmission	  between	  ALMA	  site	  (5000m)	  and	  OSF	  (2900m)	  through	  one	  fiber8	  x	  8	  Gbps DWDM	  modules
installed	  in	  June	  2014

APP	  First	   Fringe	  detection• 13	  Jan	  2015
• Short-­‐baseline	  experiments	  with	  APEX
• Full	  VLBI	  mode	  (Independent	   maser,recorder)• Fringe	  detected	  for	  0522-­‐0364(bright	  calibrator)

Fringe	  detection	  with	  SPT
• Test	  observations	  in	  Jan	  2015
• Fringe	  detected	  at	  1.3	  mm	  between	  SPT	  and	  APEX	  !!

Inter-­‐continental	  fringe	  detection	  Fringe	  detection	  at	  1.3mm	  between	  ALMA	  and	  IRAM	  30mGreen land
CARMA
ALMA

HawaiiSMTO

LMT

Pico Veleta

Pico Veleta 30m

ALMA

ALMAーPico	  Veleta fringe	  on	  29	  Mar	  2015

2.	  Our	  recent	  activity	  EHT	  activities	  in	  Japan• Science	  activities
EHT	  data	  analysis

M87	  at	  230G	  (Akiyama+	  2015)

Closure	  phase	  detected	  at	  1mm	  !

EHT	  activities	  in	  Japan• Science	  activities
EHT	  data	  analysis
mm	  VLBI	  M87	  at	  230G	  (Akiyama+)
M87	  86G	  imaging	  (Hada+)

Preliminary

M87	  with	  HSA	  at	  86G

Possible	   polarization	  at	   86G

M87	  86G	  image:	  Hada+	  in	  prep.

EHT	  activities	  in	  Japan• Science	  activities
EHT	  data	  analysis
M87	  at	  230G	  (Akiyama+)mm	  VLBI	  M87	  86G	  imaging	  (Hada+)
long-­‐mm/cm	  monitoring	  with	  VERA	  and	  KaVA (Hada+)

M87	  VHE	  and	  radio	  flare:	  	  	  Hada+(2014),	  ApJ,	  785,	  165

Super-­‐resolution	  with	  sparse	  modeling• M87	  with	  VLBA	  at	  22G/43G	  (Tazaki	  et	  al.	  in	  prep)
Super-­‐resolution	  images
24	  GHz

standard	  image

Preliminary	  Results	  ! 43	  GHz2	  mas2 mas

43	  GHz	  (Hada+)

2 2	  masmas

2 2	  masmas

This	  kind	  of	  technique	  will	  be	  powerful	  for	  BH	  imaging

3.	  Future	  ProspectNear future	  prospect• Nearly	   everything	  ready	   for	   imaging	  black	   hole	  shadow	  !?
• mm-­‐VLBI	  with	  ALMA	  will	   be	   coming	  in	   Cycle-­‐4(band	  3	  most	   certainly,	   and	   possibly	  band	   6)• EHT	   observations	  of	   Sgr A	  and	   M87	  with	  ALMAin	   early	   2017.

南極望遠鏡への期待
SPTの参加からもわかるように、（サブ）ミリ波
VLBIにとって重要な局• 優れた観測条件• 地理的要因（南北基線 etc.）• もし30ｍ鏡が出来たらインパクト大• 10mクラスでも面白い
サブミリ波南極VLBI	  ??
e.g.,	  VLBI	  at	  500	  GHz	  -­‐-­‐ 1	  THzALMA,	  南極(x2) +	  気球