S/X receiver for Parkes geodetic VLBI program

29 October 2012

ATNF, Sydney

29 October 2012

Оleg Titov (Geoscience Australia)

29 October 2012 Geoscience

Australia

IVS astrometric programs

International VLBI Service (IVS) supports several observational programs (Earth Orientation Parameters; geodesy; astrometry). All in S/X

Astrometric programs are designed for improvement and densification of the International Celestial Reference Frame (ICRF2, 2009)

Parkes participates in the IVS astrometric programs since 2004, and contributed to ICRF2.

29 October 2012 Geoscience

Australia

ICRF1 catalogue (1998)ICRF1 catalogue (1998)

Geoscience Australia

20 June 2012

1.212 defining sources with the positional accuracy ~0.25 mas

2.294 “non-defining” sources

3.102 “other” sources

608 sources separated into 3 groups

29 October 2012 Geoscience

Australia

ICRF2 catalogue (2009)ICRF2 catalogue (2009)

Geoscience Australia

1.295 defining sources with the positional accuracy ~0.04 mas

2.922 “non-defining” sources

3.1217 VCS sources

3414 sources separated into 3 groups

Geoscience

Australia29 October 2012

ICRF1

Geoscience

Australia29 October 2012

ICRF2

Geoscience

Australia29 October 2012

ICRF2

7 million group delays were measured for legacy since 1979

All done in S/X

Geoscience

Australia29 October 2012

Accuracy for 295 ‘defining’ sources

Geoscience

Australia29 October 2012

Accuracy for 1217 ‘non-defining’ sources

29 October 2012 Geoscience

Australia

ICRF2 catalogue (2009)ICRF2 catalogue (2009)

Geoscience Australia

295 defining sources with the positional accuracy ~0.04 mas

We have reached the limit of accuracy to

search for hidden systematic effects

Geoscience

Australia29 October 2012

The Galaxy

Geoscience

Australia29 October 2012

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

V

a

V

a

29 October 2012 Geoscience

Australia

Secular aberration driftSecular aberration drift

Geoscience Australia

Systematic proper motion (dipole effect) caused by the acceleration of the Solar system barycentre

P – angle between object and the Galactic centre

Psina 2R

GMa Gal

cossinsinsincos

cossincos

321

21

aaa

aa

03

002

001

sin

cossin

coscos

aa

aa

aa

Geoscience Australia

29 October 2012

directonvectoronacceleratitheof

ofscoordinate),( 00

sourcetheof

ofscoordinate),(

Analytical expression for the dipole proper motion

29 October 2012

Fanselow (1983) Observation Model and Parameter Partials for the JPL VLBI Parameter Estimation Software MASTERFITV1.0, JPL Publication 83-39.

Bastian (1995)Eubanks et al (1995)Gwinn et al (1997)Sovers, Jacobs, Fanselow (1998)Kovalevsky (2003)MacMillan (2005)Kopeikin and Makarov (2006)

References

year/as64

213103 seckma

year/as 64

40 sources observed in more > 1,000 sessions

29 October 2012

cossincos 21 aa

The dipole systematic is visually detected!

29 October 2012

Observed apparent proper motions

29 October 2012

a = 5.3 ± 1.1 as/yr toward = 268 ± 12°, = -30 ± 13°

The Dipole obtained from 643 radio sources

29 October 2012 Geoscience

Australia

Interim conclusion

We are able to detect a tiny systematic proper motion of the reference radio sources (up to 1 μas/year), free of the intrinsic motion caused by the relativistic jets.

Potentially, we could study the dynamics of the Universe by the same way as we used to study the dynamics of the Galaxy

29 October 2012 Geoscience

Australia

Redshift dependence

ALLALL(643)

0<z<0.64(128)

0.64<z<1.13

(120)

1.13<z<1.64

(132)

z>1.64(121)

Amplitude

(μas/y)

5.3 +/- 1.1

5.0 +/- 2.3 8.0 +/- 2.2 9.3 +/- 2.7 9.1 +/- 3.4

Direction 268 +/- 12

-30 +/- 13

275 +/- 30-27 +/- 30

295 +/- 20-50 +/- 16

226 +/- 19-37 +/- 18

244 +/- 21

+17 +/- 22

Weighted rms

(μas/y)

20.8 21.2 16.7 22.2 21.9

Quadrupole systematic (2012)

29 October 2012

Mean square mplitude ~ 4.3 ± 1.4 as/year

Redshift dependent

Astrometric stability: 0.2<z<1

Quadrupole sy

stematic

Dipole systematic

Covariance function

Consider correlation between two point in sphere, separated by the angular distance P

29 October 2012

ddcos)','(f),(f)P(K

One-dimensional covariance function

Correlation vs mutual angle

radian

0.0 0.5 1.0 1.5 2.0 2.5 3.0

corr

elat

ion

-0.2

-0.1

0.0

0.1

0.2

step 1 degree

29 October 2012

Correlation vs mutual angle

radian

0.0 0.5 1.0 1.5 2.0 2.5 3.0

corr

ela

tion

-0.2

-0.1

0.0

0.1

0.2

step 1 degreestep 2 degree

One-dimensional covariance function

29 October 2012

Correlation vs mutual angle

radian

0.0 0.5 1.0 1.5 2.0 2.5 3.0

corr

ela

tion

-0.2

-0.1

0.0

0.1

0.2

step 1 degreestep 2 degreesstep 5 degrees

One-dimensional covariance function

29 October 2012

29 October 2012

Spectra of two proper motion components

29 October 2012

Spectrum of vector proper motion

Geoscience

Australia29 October 2012

Accuracy for 295 ‘defining’ sources

643 measured proper motions

• DE>+40 117

• 0<DE<+40 247

• -40<DE<0 174

• DE<-40 83

• More observations are required, especially, in the southern hemisphere.

29 October 2012

Australian (AuScope) – New Zealand network

Geoscience Australia

29 October 2012

12m Antenna at Patriot12m Antenna at Patriot5 deg/sec in azimuth, 1.5 deg/sec in elevation

29 October 2012

Conclusions

• Positions of the reference radio sources are likely to be affected by positional instabilities, random or systematic

• Cosmologic signals may be presented.

• More observations are required, especially, in the southern hemisphere.

29 October 2012

Plans

• ICRF3 to be approved by IAU GA in 2018

• IVS is planning to run am intensive astrometric program since 1, July, 2013.

• Southern Hemisphere is the area of special attention

• AuScope network to play a key role

• Parkes (with S/X receiver) is very important for observing of weak quasars for ICRF densification

29 October 2012

Thank you!

29 October 2012

29 October 2012 Geoscience

Australia

Reference frames

Inertial – no acceleration of the origin, no rotation of reference axes

Non-inertial – non-zero acceleration, rotation of reference axes is permitted

Quasi-inertial – acceleration of the origin is permitted, no rotation of references axes

29 October 2012 Geoscience

Australia

ICRS definition

Assumption (1995)

“The reference radio sources have no measurable proper motion

[at the level of precision achieved to 1995]”

The secular acceleration drift (dipole effect) is not considered by the current ICRS assumptions and IERS conventions - tbd

29 October 2012

...]...)(2

1)(

)([

HueeEeuer

ehdt

de

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

σ – Shear

ω - Rotation

E – electric-type gravitational waves

H – magnetic-type gravitational waves

The Dipole obtained from 555 radio sources

a = 6.4 ± 1.5 as/yr toward = 263 ± 11°, = -20 ± 12°29 October 2012

29 October 2012 Geoscience

Australia

Solution of 2010 [Titov, Lambert, Gontier, A&A

(2011), 529, A91]

555 sources

0.7 +/- 1.1 μas/y -5.9 +/- 1.2 μas/y -2.2 +/- 1.2 μas/y

Amplitude

6.4 +/- 1.3 μas/y

RA = 263 +/- 11DE = -20 +/- 12

chi-sq = 1.5

wrms = 23.0 μas/y

Solution of 2012

643 sources

0.2 +/- 1.0 μas/y -4.5 +/- 1.1 μas/y -2.6 +/- 1.2 μas/y

Amplitude

5.3 +/- 1.1 μas/y

RA = 268 +/- 12DE = -30 +/- 13

chi-sq = 1.3

wrms = 20.8 μas/y

Conclusions

• The dipole effect does exist and is aligned with the theoretical prophecy.

• More distant radio sources (z>1.134) look less stable. It is important for future radio ICRF realizations.

• Cosmologic signals may be presented.

• Spectroscopic observations are essential.

29 October 2012

Part II

•Spectroscopic observations of reference radio sources (mostly in the southern hemisphere)

29 October 2012

29 October 2012

Team members:

David Jauncey (ATNF, CSIRO)Dick Hunstead, Helen Johnston (Uni of Sydney)Tapio Pursimo (Nordic Optical Telescope)Zinovy Malkin, Kirill Maslennikov, Alexandra Boldycheva (Pulkovo Observatory)Laura Stanford (Geoscience Australia)

How to implement the effect?

29 October 2012

Two ways (at least)Two ways (at least)

1. Introduce non-zero systematic proper motion at the level of IAU Resolutions

2. Incorporate the galactocentric acceleration to the conventional group delay model (IERS Conventions)

29 October 2012

))((1

1

)2

)(1)((

1)(

2

21

)(

2

222

2

2

2

wVsc

c

sVVb

cc

wV

c

V

c

U

c

sbgrav

Conventional group delay model

))((1

1

)2

)(1))(((

1)(2

21

)(

2

222

2

2

2

wtaVsc

csV

taVbcc

wVc

V

cU

csb

grav

Titov, Astronomy Report (2011), 55(1), 9529 October 2012