03/000 Cosmologic astrometry Australian Government Geoscience Australia Yonsei University, Seoul 18 October 2010

Geoscience Australia 18 October 2010

The concept Geoscience Australia 18 October 2010 B   B = km,  = 0.03 cos  sec

ICRF2 defining sources 18 October 2010

ICRF1 → ICRF → 2010 total number of objects 608 → 3414 number of defining sources 212 → 295 formal error σ(0) = 60 µas → 7 µas “inflated” error σ = 250 µas → 41 µas Geoscience Australia 18 October 2010

Astrometry of stars (~2000 years) ↓ Astrometry of quasars Geoscience Australia 18 October 2010 no structure huge variable structure

ICRF source instability (structure) Geoscience Australia 18 October 2010

Instability of the ICRF sources ( ) Geoscience Australia 18 October 2010

Instability of ICRF sources ( , in sky plane, ) Geoscience Australia 18 October 2010 Kellermann et al. (2004) Position angle of the brightest jet ~ 158º Geodetic VLBI: Position angle ~ 148º apparent proper motion ~ 0.6 mas/year

October 2010

Change of position of a celestial object approximated by linear trend Geoscience Australia 18 October 2010 Definition of proper motion

October 2010

The apparent motions look random The systematic has been searched since (Gwinn, Eubanks et al. 1997; MacMillan 2003) Geoscience Australia 18 October 2010

Apparent motion 18 October 2010

FK5 → ICRF → 2010 position accuracy 0”.019= µas → 41 µas apparent motion accuracy 700 µas/year → µas/year Geoscience Australia 18 October 2010

Assumption (1995) “The reference radio sources have no measurable proper motion [ at the level of precision achieved by 1995 ]” Geoscience Australia 18 October 2010

Possible reasons of the assumption violation 1. Secular aberration drift (Bastian, 1995; Sovers et al., 1998, Klioner, 2003) 18 October 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 Geoscience Australia 18 October Centrifugal acceleration due to rotation of the Solar system around the Galaxy center

Geoscience Australia 18 October Centrifugal acceleration due to rotation of the Solar system around the Galaxy center

Geoscience Australia 18 October Centrifugal acceleration due to rotation of the Solar system around the Galaxy center V a V a

Geoscience Australia 18 October All quasars are attracted by the Galactic centre

Geoscience Australia 18 October Centrifugal acceleration due to rotation of the Solar system Volatile!

2 и 3 18 October 2010 Proper motion in the expanding Universe (Kristian and Sachs, 1966) “Observations in cosmology”

2. The Hubble law 18 October 2010 The Earth H - the Hubble constant It is supposed to be isotropic for all directions on the sky

2. Hubble constant anisotropy 18 October generalised Hubble expansion

18 October 2010 The Hubble law Anisotropic Hubble expansion and non- zero systematic 2. Hubble constant anisotropy

3. Primordial gravitational waves (Kristian and Sachs, 1966) 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 3. Primordial gravitational waves

Only three reasons are considered Geoscience Australia 18 October Dipole systematic 2. Rotation (no physics yet) 3. Gravitational waves and Hubble constant anisotropy

Proper motion model 18 October 2010 rotation Magnetic-type Gravitational waves Electric-type gravitational waves or Hubble constant anisotropy dipole

Proper motion model 18 October 2010 dipole rotation

18 October 2010 Systematic effect in apparent motion

This is not effect of intrinsic structure! Geoscience Australia 18 October 2010

~ hour sessions since 1980 ~ 6 million delays ~ 3000 sources Software CALC/SOLVE (S.Lambert, A.-M. Gontier; Paris Observatory) Geoscience Australia 18 October 2010 Global solution

Proper motion model 18 October 2010 dipole rotation

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

Quadrupole effect in apparent proper motion – component E(2,1)

18 October 2010 Quadrupole effect in apparent proper motion – component E(2,0)

Geoscience Australia 18 October 2010 Main results - Quadrupole systematic is marginal A = 3.5 +/- 0.9 μas Energy density of primordial gravitational waves Too much uncertainty!!!

- Galactocentric acceleration Geoscience Australia 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

Geoscience Australia 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 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