""Stellar-Mass, Intermediate-Mass, andStellar-Mass, Intermediate-Mass, and Supermassive Supermassive Black Holes" Black Holes"

Kyoto International Community House, Kyoto, JapanKyoto International Community House, Kyoto, JapanOctober 28 - 31, 2003October 28 - 31, 2003

　 Direct imaging of a super massive black hole, SgrA*

M.Miyoshi, Pepe Ishitsuka, S. Kameno (NAOJ),

Z. Shen (Shanghai Astronomical Obs.) ＆ S. Horiuchi (SKA)

Imaging the vicinity of black hole is one of the ultimate goals of VLBI astronomy. SgrA*, the closest super massive black hole, located at our Galactic center is the leading candidate for such observations. Because of the apparent Schwarzschild radius is estimated to be larger than 6- micro arc seconds from the mass (2.6-3.7*10^6 solar mass) and the distance (8 kpc), the corresponding shadow of black hole is 30 micro arc seconds in diameter and because mm and sub-mm VLBI will soon obtain the sufficient spatial resolutions for the imaging. Recent detections of the rapid flaring from a few hours to 30 min at mm-wave, infrared, and x-ray emissions mean that the structure of the black hole system of SgrA* will also change rapidly. One of VLBA observations at 43GHz really shows such rapid changes of structure of SgrA* occur. We also show performance of a supposing but realistic ground-based mm and sub-mm VLBI array for imaging the SgrA* black hole system.

A simulation of the appearance of black hole with accretion A simulation of the appearance of black hole with accretion disk (Fukue et al 1989). Light from the other side is bended disk (Fukue et al 1989). Light from the other side is bended by the black hole gravity, and then we can see opposite sidby the black hole gravity, and then we can see opposite side. At the center ‘black hole ‘ can be seen from where no lighe. At the center ‘black hole ‘ can be seen from where no light come towards us.t come towards us. 　　　　　　http://quasar.cc.osaka-kyoiku.ac.jp/~fukue/http://quasar.cc.osaka-kyoiku.ac.jp/~fukue/

See also Fukue’s poster in this meeting.

Radio Interferometer has been trying to resolve the central part o

f the monsters. Above all, VLBIs have the best instruments for investigating fine structures of the s

ources.

The nucleus of M87 (VLA,VLBA ）This is one of the highest resolution VLBI maps. But, the true face of central massive black hole cannot be seen.As you already saw at Hirabayashi’s talk

So we must check. So we must check. How small are the black holes?How small are the black holes?

～５ RsTakahashi & Mineshige (2003)

See also Takahashi’s poster in this meeting.

Shadow Size of Black Holes

If you want to look If you want to look a black hole (shadow),a black hole (shadow),

ＳｇｒＡ＊ ＳｇｒＡ＊ should be observeshould be observedd

because it is the biggest.because it is the biggest.

Our galactic central black holeOur galactic central black holeＳｇｒＡ＊ＳｇｒＡ＊ is is

the most convincing black hole the most convincing black hole candidate.candidate.

SgrA* is now the best convincing MBH.

M=3.65±0.25×106 M. Eisenhauer et al. 2003

ＮＧＣ４２５８の中心核周円盤（３９００万太陽質量）

Herrnstein et al 1999

Miyoshi et al 1995

NGC4258 is the second one.

# Eckart’s talk

Our galactic central black holeOur galactic central black holeＳｇｒＡ＊ＳｇｒＡ＊ is is

not only the most convincing blnot only the most convincing black hole candidate,ack hole candidate,

but now also showsbut now also shows some activities some activities

though not so spectacular as though not so spectacular as its’ old days (# Koyama’s talk).its’ old days (# Koyama’s talk).

Zhao et al 2003

２３０ＧＨｚ

１５，２２ＧＨｚ

ＳｇｒＡ＊Periodic Variation with 106day circle,Corresponding Flares at 230GHz

Our Galactic central BHOur Galactic central BH ，，ＳｇｒＡ＊ＳｇｒＡ＊ Rapid changes of its intensity Rapid changes of its intensity

are revealed recently. are revealed recently.X ray flare (Td=10^4 –3×10^3sec)　 (Baganoff et al. 2001, Porquet et al. 2003) 　

IR flare up for about 30 min 　 (Genzel et al. 2003)

Radio flare up 　 at mm-wave length 　 (Miyazaki, Tsutsumi & Tsuboi 準備中 ) 　

Duration ~ Td=10^4 – 3*10^3 sec

Time

我々我々のの銀河中心ＢＨ銀河中心ＢＨ，，ＳｇｒＡ＊ＳｇｒＡ＊Short Time Flare of Short Time Flare of ＸＸ ray ray

((Baganoff et al 01, Porquet et al 03Baganoff et al 01, Porquet et al 03))

Baganoff et al 01Baganoff et al 01

Our Galactic central BHOur Galactic central BH ，，ＳｇｒＡ＊ＳｇｒＡ＊ Rapid changes of its intensity Rapid changes of its intensity

are revealed recently. are revealed recently.X ray flare (Td=10^4 –3×10^3sec)　 (Baganoff et al. 2001, Porquet et al. 2003) 　

IR flare up for about 30 min 　 (Genzel et al. 2003)

Radio flare up 　 at mm-wave length 　 (Miyazaki, Tsutsumi & Tsuboi 準備中 ) 　

我々の銀河中心ＢＨ，ＳｇｒＡ＊

Flare at NIR about 30min. Genzel et al. 2003　　　　　　　　　　 (Nature today ）

# Eckart’s talk

Our Galactic central BHOur Galactic central BH ，，ＳｇｒＡ＊ＳｇｒＡ＊ Rapid changes of its intensity Rapid changes of its intensity

are revealed recently. are revealed recently.X ray flare (Td=10^4 –3×10^3sec)　 (Baganoff et al. 2001, Porquet et al. 2003) 　

IR flare up for about 30 min 　 (Genzel et al. 2003)

Radio flare up 　 at mm-wave length 　 (Miyazaki, Tsutsumi & Tsuboi 準備中 ) 　

Td=2*10^3 sec

我々我々のの銀河中心ＢＨ銀河中心ＢＨ，，ＳｇｒＡＳｇｒＡ＊

Short Time FlareShort Time Flare

at mm-waveat mm-wave ((Miyazaki et al.Miyazaki et al.

準備中 準備中 ))

Next day

With Nobeyama mm array (NMA)

Structural change of SgrA* (43GHz)Structural change of SgrA* (43GHz)

15min integration each （ 3mas*6mas ）

Time

Ｍｉｙｏｓｈｉ ｅｔ ａｌ．準備中

Flu

x D

ensi

ty(J

y)

0115UT-0700UT

3mas=24au@8kpcor

500Rs(2.6*10^6Msun)

Kato,Mineshige & Shibata 03See Kato’s poster

← An example of testing performance

2) Simplification and Generalization of the reduction procedure from which the images derived. The procedure will be useful for mm-VLBI where atmospheric fluctuations often damage the data.

1)Tests of performance of the snap shot observation mode with VLBA

I must do two things before publication of the results.

SS ｇｒＡ＊ｇｒＡ＊ is is not only the most convincing blnot only the most convincing bl

ack hole candidate,ack hole candidate,

but now also showsbut now also shows some activities, has become some activities, has become

interestinginterestingHowever one nuisance remains.However one nuisance remains.

Scattering by surrounding plasmaScattering by surrounding plasma

VLBI images of the SgrA* from 5GHz to 43GHz. from Ｌｏ　ｅｔ　ａｌ　（１９９９）

The intrinsic image is blurred and broadened because of scattering effect.

Apparent Size of SgrA*

Free from Scattering Effects by Plasma

（∝ λ ＾２）At mm-, sub-mm wave

length !

So we can expect observe the intrinsic

image at mm-, sub-mm wave length.

Ｄｏｌｌｍａｎｎ　ｅｔ　ａｌ．　（２００１）

Shen et al. Shen et al. (200(200４４ ))

VLBA 86 GH ｚ

１ｍａｓ

SgrA*

This is the result from the highest frequency VLBI.

SgrA* should be observed at SgrA* should be observed at mm to sub-mm VLBImm to sub-mm VLBI

if you want to look black hole.if you want to look black hole.

First,First,Can we get the image of the Can we get the image of the black hole shadow of SgrA* black hole shadow of SgrA*

with 86GHz VLBA?with 86GHz VLBA?

note. VLBA 86GHz observations of SgrA* is really important to measure the intrinsic size.

See deeply the Poster of Shen et al. at this meeting.

Image Model

Observed typical image

+Black Hole Shadow

(30×24μas 　PA=80° ）

VLBA VLBA+ Huancayo+ALMA+SEST 　　さかさＶＬＢＡ at south

Here in order to estimate the performance of spatial resolutions of several arrays, ignoring scattering effects and weather conditions, but using the real sensitivities, we made clean simulations. At 86GHz ground based VLBI, the shadow of SgrA* will not be detected only because insufficient spatial resolutions.

Then,Then,What kind of sub-mm VLBI arrayWhat kind of sub-mm VLBI arrayshould we construct for imaging should we construct for imaging the black hole shadow of SgrA*?the black hole shadow of SgrA*?

I made simulations with three I made simulations with three types of arrays.types of arrays.

ＳｇｒＡ＊ locates at δ ＝－３０ °,

Observations from the southern hemisphere is preferable.

２５ｍ鏡１０台最大８０００ km 基線（最小フリンジ間隔０．２ mas ＠４３ＧＨｚ）３００ＭＨｚ～ 86 ＧＨｚ

Case 1. VLBA

NOTE. VLBA antennas do not have sufficient surface accuracy

to receive sub mm radio waves.

2005: High site is fully operational

BIMA

Photo by Ota NaomiSMA

ALMA

OVRO

SEST

Huancayo

virtualCase2.

realistic sub mm Stations

ＶＬＢＡ（ VLBI 　Array ）

Ｎｏｒｔｈ　　北

南Ｓｏｕｔｈ

Case 3.

Ｉｎｖｅｒｓｅｄ　ＶＬＢＡ（さかさＶＬＢＡ）

• 　 uv coverage for SgrA*

１．５　 mas＠８６Ｇ0.56mas@230GHz

1.VLBA 　　　　　　　　　　 2.SMA+CARMA+Huancayo+ALMA+SEST 　　　　　　 3. さかさＶＬＢＡ

• 　 dirty beam for SgrA*

Gaussian 0.1×0.08mas, PA=80°,f=3Jy Black Hole Shadow 30×24μas 　PA=80°

230GHzsimulations

250μasSuper resolution(20μas beam) 使用

Outer size 0.1mas

from Krichbaum obs

1.VLBA 2.SMA+CARMA+Huancayo+ALMA+SEST 　　　　　　 3. さかさＶＬＢＡ

Good image was obtained

from ‘inversed VLBA’ as expected

In order to image the black hole of In order to image the black hole of SgrA*, we must observe with sub-mm SgrA*, we must observe with sub-mm

VLBI.VLBI.

We need the same scale array like VLBA, (8000km,10 Stations, same sensitivity as that

of 86GHz of real VLBA)

located at the southern hemisphere.

model Image from simulation

But, How about sub-mm VLBI But, How about sub-mm VLBI with small number of stations?with small number of stations?

Is it useless for investigating the black hole shadow of SgrA*?

model Image from simulation

We can estimate the shadow size and then the BH mass with submm VLBI including only small number of stations.b

Null point shifts with the size of BH shadow, namely BH mass

ＢＨ　２．６ × １０＾６Ｍｓ Ds= ３０ μ

ａｓ

NO Black holeNO Shadow

An Example of the relation of Visibility Amplitudes and Structure of S ｇｒＡ＊ （２３０ＧＨｚ）ＢＨ　 ３．７ × １０＾６

ＭｓDs= ４４ μ ａｓ

Huancayo

ＳＥＳＴ１５ｍ鏡（ＥＳＯ）

ＡＬＭＡ（日米欧）1960km

800km

1520km

South America

Photo by Ota Naomi

Virtual now

Construction begins

Since 1987

Old 32m communication antenna

In order to image Black Hole directly:

1)the first and best target should be SgrA*

SgrA* has the biggest apparent size of black hole shadow (D=30-45 micro arc sec )

SgrA* shows short time flares, then we can expect to investigate the active phenomena occurring on accretion disk.

2) Sub mm VLBI (230GHz or higher frequency)

with like VLBA location (=10 stations & 8000km ) in southern hemisphere is needed to image clearly.

However, from visibility analysis with image models we can begin to investigate BH shadow even with sub-

mm VLBI using only small number of stations.

Conclusions

So We Should Start sub-mm VLBI

at the Southern Hemisphere at once!

Image of an optically thin emission region surrounding a black hole with the characteristics of Sgr A* at the Galactic center. The black hole is here either (a c) maximally rotating (a* = 0.998) or (d f) nonrotating (a* = 0). The emitting gas is assumed to be in free fall with an emissivity proportional to r-2 (top panels) or on Keplerian shells (bottom panels) with a uniform emissivity (viewing angle i = 45 ). (a, d) GR ray-tracing calculations; (b, e) images seen by an idealized VLBI array at 0.6 mm wavelength, taking interstellar scattering into account; and (c, f) images seen for a wavelength of 1.3 mm. The intensity variations along the x-axis (solid green curve) and the y-axis (dashed purple curve) are overlayed. The vertical axes show the intensity of the curves in arbitrary units, and the horizontal axes shows the distance from the black hole in units of Rg, which, for Sgr A*, is 3.9 × 1011 cm 3 as.　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　Ｆａｌｃｋｅ et　 al　 （２０００）

回転あり

回転なし

　 　 　 　 　実像 VLBI 　 　像０．６ミリ VLBI像１．３ミリ

SgrA* Black Hole Shadow (Falcke et al 00)

Thanks Thanks !!