03/000 Cosmologic astrometry Australian Government Geoscience Australia Yonsei University, Seoul 18...

03/000

Cosmologic astrometry

Australian Government

Geoscience Australia

Yonsei University, Seoul

18 October 2010


18 October 2010

The concept

;cos12 c

BTT

1T


18 October 2010

B

B = 10000 km,

= 0.03cos sec

2T

ICRF2 defining sources

18 October 2010

ICRF1 → ICRF21995 → 2010

total number of objects 608 → 3414number of defining sources 212 →

295

formal error σ(0) = 60 µas → 7 µas

“inflated” error σ = 250 µas → 41 µas 22

02 )250()5.1( as 22

02 )40()5.1( as


18 October 2010

40

60

Astrometry of stars (~2000 years)

↓ Astrometry of quasars


18 October 2010

no structure huge variable structure

ICRF source instability(structure)


18 October 2010

Instability of the ICRF sources (2201+315)

Variations of the 2201+315, RA

Year

2000 2001 2002 2003 2004 2005 2006

as

-2000

-1500

-1000

-500

0

500

1000

1500


18 October 2010

Variations of the 2201+315, DEC

Year

2000 2001 2002 2003 2004 2005 2006

as

-2000

-1500

-1000

-500

0

500

1000

1500

Instability of ICRF sources ( 2201+315, in sky plane, 2001-2004)

as

-1000-50005001000

as

-1000

-500

0

500

1000

Daily dataApproximation


18 October 2010

Kellermann et al. (2004)

Position angle of the brightest jet ~ 158ºGeodetic VLBI:

Position angle ~ 148º apparent proper motion ~ 0.6 mas/year

2145+067

1994 1996 1998 2000 2002 2004

as

-2000

-1000

0

1000

2000

18 October 2010

Change of position of a celestial object approximated

by linear trend

0t


18 October 2010

Definition of proper motion

t

)()()( 00 tttt

2145+067

18 October 2010

RA, 2145+067

Year

1990 1995 2000 2005 2010

sec

-0.0002

-0.0001

0.0000

0.0001

0.0002

The apparent motions look random

The systematic has been searched since

(Gwinn, Eubanks et al. 1997; MacMillan 2003)


18 October 2010

Apparent motion

18 October 2010

FK5 → ICRF2

1988 → 2010

position accuracy 0”.019= 19000 µas → 41 µas

apparent motion accuracy 700 µas/year → 10-100

µas/year


18 October 2010

Assumption (1995)

“The reference radio sources have no measurable

proper motion [at the level of precision achieved by

1995]”


18 October 2010

Possible reasons of the assumption violation

1. Secular aberration drift (Bastian, 1995; Sovers et al., 1998, Klioner,

2003)

18 October 2010

2. Hubble constant anisotropy (Kristian and Sachs, 1966)

3. Primordial gravitational waves (Kristian and Sachs, 1966; Pyne et al., 1996)

4. Motion of the Solar system with respect CMB

Kardashev (1986), Sovers et al (1998) <14 µas/year (Galaxy M81)

Directed towards the centre of Galaxy(RA= 270º, DE = -30º) a = V²/R


18 October 2010

yearaskma /4sec/102 213

1. Centrifugal acceleration due to rotation of the Solar system

around the Galaxy center


18 October 2010

1. Centrifugal acceleration due to rotation of the Solar system around the Galaxy center


18 October 2010

1. Centrifugal acceleration due to rotation of the Solar system around the Galaxy center

V

a

V

a


18 October 2010

1. All quasars are attracted by the Galactic centre

cossinsinsincos

cossincos

321

21

aaa

aa

03

002

001

sin

cossin

coscos

aa

aa

aa


18 October 2010

directonvectoronacceleratitheof

ofscoordinate),( 00 sourcetheof

ofscoordinate),(

1. Centrifugal acceleration due to rotation of the Solar system

Volatile!

2 и 3

18 October 2010

...]...)(2

1)(

)([

HueeEeuer

ehdt

de

Proper motion in the expanding Universe (Kristian and Sachs, 1966) “Observations in

cosmology”

2. The Hubble law

18 October 2010

The Earth

HrV

H - the Hubble constant

It is supposed to be isotropic for all directions on the sky

2. Hubble constant anisotropy

332211 ,, eee

reeeeeHV

2

22112

221133 cos2cos)(2

1sin))(

2

1(

cos2sin)(2

12211 ee

cossin2cos))(2

1cossin))(

2

1( 2211221133 eeeee

18 October 2010

- generalised Hubble expansion )(5.0 2211 eeH

332211 eee Heee 332211

rHV ),( HrV

00

18 October 2010

The Hubble law

00

Anisotropic Hubble

expansion and non-zero

systematic

2. Hubble constant anisotropy

3. Primordial gravitational waves

(Kristian and Sachs, 1966)

...]...)(2

1)(

)([

HueeEeuer

ehdt

de

18 October 2010

σ – “Shear”

ω - rotation

E – Electric-type gravitational waves

H – Magnetic-type gravitational waves

18 October 2010

Gwinn et al (1997) – power density of gravitational waves

2

),(

),(,22

0

2

10

3 mME

MEmGW a

H

yearasMpckmH /12sec102sec*/60 1180

3. Primordial gravitational waves

Only three reasons are considered


18 October 2010

1. Dipole systematic2. Rotation (no physics yet)3. Gravitational waves and Hubble constant anisotropy

Proper motion model

18 October 2010

rotation

2

2,2,2,2,2

1

1,1,1

1

1,1,1 )(),(

m

Mm

Mm

Em

Em

m

Mm

Mm

m

Em

Em YaYaYaYa

Magnetic-type

Gravitational waves

Electric-type gravitational waves or Hubble constant anisotropy

dipole

Proper motion model

)cossin(1

)cossinsinsincos(1

)cossinsinsincos(1

)cossin(1

cos

21321

32121

caaa

c

caa

c

18 October 2010

dipole

rotation

18 October 2010

Systematic effect in apparent motion

This is not effect of intrinsic structure!


18 October 2010

~ 5000 24-hour sessions since 1980 ~ 6 million delays~ 3000 sources

Software CALC/SOLVE (S.Lambert, A.-M. Gontier; Paris Observatory)


18 October 2010

Global solution

Proper motion model

)cossin(1

)cossinsinsincos(1

)cossinsinsincos(1

)cossin(1

cos

21321

32121

caaa

c

caa

c

18 October 2010

dipole rotation

0.16.1

8.05.5

7.06.0

3

2

1

a

a

a

7.07.0

9.06.0

9.05.1

3

2

1

Dipole effect in apparent proper motion

18 October 2010

α = 266º +/-8º

δ= -18º+/- 18º

A = 5.8 +/- 1.4 μas

18 October 2010

Quadrupole effect in apparent proper motion

18 October 2010

18 October 2010

Quadrupole effect in apparent proper motion – component

E(2,1)

18 October 2010

Quadrupole effect in apparent proper motion – component

E(2,0)


18 October 2010

Main results- Quadrupole systematic is marginal A = 3.5 +/- 0.9 μas

Energy density of primordial gravitational waves

20002.00031.0 hGW

Too much uncertainty!!!

- Galactocentric acceleration

213 sec/10)7.0(0.3 km


18 October 2010

Dipole effect α = 266º +/-8º

δ = -18º+/- 18º

A = 5.8 +/- 1.4 μas

Main results

First direct identification of Galactocenrtic acceleration of the Solar system barycentre


18 October 2010

Main results

Problems for ICRS definition

Assumption (1995)

“The reference radio sources have no measurable proper motion

[at the level of precision achieved by 1995]”

The secular acceleration drift (dipole effect) is not taken into account by the current ICRS definition/assumption

Question

18 October 2010

If proper motion are real, then the reference axes

are not fixed by the positions of the defining sources!

How to deal with the non-zero proper motion???

Conclusion

• Secular aberration drift has been found.

• Fundamental astrometry has a strong cosmologic component

• Geodetic VLBI is able to measure apparent motion of several

thousand reference radio sources and promote some fundamental

discoveries about the Universe

• Attract more resources (funds, grants, students) and public/media

attention

18 October 2010

Suggestion• Modify the IVS observational program to obtain about 3000 proper

motion by 2020 (instead of 700).

• This number increases very slowly, from ~500 in 2001 to ~700 in 2010.

Just because existing IVS observational programs target on the well-

known sources with long observational history. New sources are

observed rarely.

• To organize a dedicated astrometric program in the southern

hemisphere. New AuScope network + New Zealand dish + Asia-Pacific

network + Kokee.

18 October 2010

Thank you!

18 October 2010

03/000 Cosmologic astrometry Australian Government Geoscience Australia Yonsei University, Seoul 18...

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