Black Hole Imagingwith EHT and Sparse Modeling

Fumie Tazaki (NAOJ)Mareki Honma, Kazunori Akiyama, Kazuhiro Hada,

& Tomoaki Oyama (NAOJ)

Self Introduction

Fumie Tazaki (田崎文得)

• PhD @Kyoto University in March 2014

• “Study of Radio-Loud Active Galactic Nuclei with X-Ray Observations”

• Main Work: Development of a system to reproduce super-resolution images with “sparse modeling.”

Scientific Goal: Snapshot of Black Hole

by Subaru/NAOJ

• Supermassive black holes exist in the center of most galaxies.

• However, no one has taken a picture of the black hole shadow.

• If we succeed,..✤ It will be the ultimate evidence of black holes.✤ We will know the environment around black holes

(e.g., mass accretion processes, formation of jets, and particle acceleration). Active black hole image

by NASA

Angular Radius of Supermassive Black Holes

Shadow Diameter ~ several x Black Hole Radius

Source Black Hole Mass (Msolar)

Distance(light-year)

Black Hole Radius (µas)

Sgr A*(milky way center)

4 x 106 2 x 104 10

M87 (3−6) x 109 7 x 107 3−7

M104 1 x 109 6 x 107 2

Cen A 5 x 107 3 x 107 0.25

The spatial resolution of a few tens μas is required for black hole shadow imaging.

Event Horizon Telescope (EHT)Global mm/sub-mm VLBI array, including ALMA!

Hawaii

CARMA SMTO

ASTE/APEX

Pico Veleta

Planned Array around 2015

Green land�

ALMA�

LMT�

Wavelength : 1.3 mm / 230 GHz (0.85 mm / 345 GHz in future)Spatial Resolution (λ/D) : ~ 40-60 μas @ 1.3 mm, (~ 10-20 μas in future)

South Pole

( )

Hardware Contribution:ALMA Phase-up Project (APP)

• Adding ALMA to EHT as a VLBI station

• Contribution by Japanese team

✤ Developed and tested the optical fiber link system in Japan.

✤ Installed the optical fiber link system on ALMA in 2014.

✤ Performed the setup test in 2014.

Optical Fiber Link System:✓ connect between ALMA/OSF and AOS✓ 8Gb/s x 8ch

Science Contribution: M87 Observation Radio flares were detected with VERA at the radio core, following after a TeV γ-ray flare in 2012.

Hada et al. (2014)

Detection of a high energy phenomenon in the vicinity of the black hole (< 0.1 light-year, < 60 RBH)!

2011 2012 γ-ray flare

VERA 43GHz core (total)VERA 43GHz core (peak 0.6 mas)

VERA 22GHz core (total)VERA 22GHz core (peak 0.6 mas)

EHT has so tiny angular resolution that cannot detect TeV γ-ray flare region (< 0.1 light-year, < 60 RBH).Akiyama et al. to be submitted

Inconsistency between Hada+ and EHT observation?

✤ Flux increase is detected within ~ 1 mas (60 RBH).

✤ Flux does not change in ~ 0.3 mas (20 RBH).

black hole

TeV γ-ray flare region

~ 1

mas

~ 0.

3 m

as

2009 data (black)

2012 data (colored)

Core Flux Density in 2012

Core Flux Density in 2009

EHT Baseline (109 λ)0.0 2.0 4.0

Cor

rela

ted

Flux

Den

sity

(Jy)

~ 0.3 mas

Science Contribution: M87 Observation

Which model is acceptable?

Approaching Jet

Counter Jet

An optimal model will be obtained by long baseline observations.

Simulated Image (Akiyama et al. to be submitted)

Science Contribution: M87 Observation

Simulated and Observed Closure Phases

Gas Accretion Disk

error ~ a few degrees

Software Contribution:Development of Super-Resolution Technique

Can we draw black hole shadows?✤ With CLEAN → NO!✤ With Sparse Modeling → YES!

Simulated image of M87 black hole (small mass end and large noise)(Honma et al. 2014)

Pseudo image CLEAN image Sparse modeling image

Applying sparse modeling to real data

VLBA data of M87

Standard Imaging(Hada et al. 2013)

Sparse Modeling(Tazaki et al. in prep.)

4 mas 4 mas

4 mas43 GHz 24 GHz

Preliminary

Clear jet’s limb and counter-jet are reproduced!

Software Contribution:Development of Super-Resolution Technique

Summary✤ Adding ALMA to EHT is going well.✤ Japanese group is contributing to

- ALMA phase-up project (APP).- science of M87.- development of imaging method with “sparse modeling.”

Black hole shadow will be coming soon!

Future Plan✤ Evaluation exam. of APP and ALMA-APEX test in 2015.✤ Test observation of the full EHT in 2015 or 2016.✤ The open use is also under consideration in the long-

term plan.