HighPrecision Astrometry of the S 5 polarcap sources

High-Precision Astrometry of the S 5 polarcap sources Jose C. Guirado (Univ. Valencia) & J. M. Marcaide (UV), I. Martí-Vidal (MPIf. R), S. Jiménez (UV), E. Ros (UV)

The S 5 Polar Cap Sample • Studied in MPIf. R since 80 s (Eckart et al. , 1987, Witzel et al. , 1988, etc. ) • Flat spectrum Radiosources: • 8 QSOs • 5 BL-Lac objects

GLOBAL HIGH-PRECISION ASTROMETRY

GLOBAL HIGH-PRECISION ASTROMETRY

GLOBAL HIGH-PRECISION ASTROMETRY Epoch 1 Epoch 2 We can study astrometric variations in time and/or frequency

GLOBAL HIGH-PRECISION ASTROMETRY astrometric variations in time and/or frequency

GLOBAL HIGH-PRECISION ASTROMETRY astrometric variations in time and/or frequency

GLOBAL HIGH-PRECISION ASTROMETRY astrometric variations in time and/or frequency

GLOBAL HIGH-PRECISION ASTROMETRY astrometric variations in time and/or frequency

VLBA OBSERVATIONS Epoch 1997. 93 1999. 41 1999. 57 2000. 46 2001. 04 2001. 09 2001. 71 2004. 53 2004. 62 2005. 45 Frequency (GHz) 8. 4 15. 4 43

PHASE-DELAY ASTROMETRY • Relative separation determination by means of least squares fits: • Homogeneous sampling of all sources at different frequencies.

The Fitting Model (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 30 ms 5 -9 ns (E=90º) + str ( , t) + instrum (t) 0 -300 ps 1 ps/s 0. 1 -3 ns (E=90º)

T A EC N TO D R NI M ELA CS, O T T D IV ID EL I E S ST S, IC The Fitting Model (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 30 ms 5 -9 ns (E=90º) + str ( , t) + instrum (t) 0 -300 ps 1 ps/s 0. 1 -3 ns (E=90º)

M M ET EA EO SU RO RE L M OG EN Y TS T A EC N TO D R NI M ELA CS, O T T D IV ID EL I E S ST S, IC The Fitting Model (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 30 ms 5 -9 ns (E=90º) + str ( , t) + instrum (t) 0 -300 ps 1 ps/s 0. 1 -3 ns (E=90º)

) ES TA BL M M ET EA EO SU RO RE L M OG EN Y TS T A EC N TO D R NI M ELA CS, O T T D IV ID EL I E S ST S, IC The Fitting Model 5 -9 ns (E=90º) + str ( , t) + instrum (t) 0 -300 ps 1 ps/s (IO PS G 30 ms N EX (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 0. 1 -3 ns (E=90º)

) ES TA BL M M ET EA EO SU RO RE L M OG EN Y TS T A EC N TO D R NI M ELA CS, O T T D IV ID EL I E S ST S, IC The Fitting Model 5 -9 ns (E=90º) RA M D AP IO S SO O U F RC E S + str ( , t) + instrum (t) 0 -300 ps 1 ps/s (IO PS G 30 ms N EX (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 0. 1 -3 ns (E=90º)

) ES TA BL M M ET EA EO SU RO RE L M OG EN Y TS T A EC N TO D R NI M ELA CS, O T T D IV ID EL I E S ST S, IC The Fitting Model 5 -9 ns (E=90º) M TI ES F 1 ps/s LS 0 -300 ps W RA M D AP IO S SO O U F RC E S A TE + str ( , t) + instrum (t) (IO PS G 30 ms N EX (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 0. 1 -3 ns (E=90º)

) ES TA BL M M ET EA EO SU RO RE L M OG EN Y TS T A EC N TO D R NI M ELA CS, O T T D IV ID EL I E S ST S, IC The Fitting Model 5 -9 ns (E=90º) (IO PS G 30 ms N EX (t) = geo (t) + trop (E(t)) + ion ( , E(t)) + 0. 1 -3 ns (E=90º) M TI ES F 1 ps/s LS 0 -300 ps W RA M D AP IO S SO O U F RC E S A TE + str ( , t) + instrum (t) The Fitting Software • Geometric model and fitting procedures computed with the University of Valencia Precision Astrometry Package (UVPAP): - Possibility of multisource differential astrometry

The Fitting Strategy • Find a preliminary model by fitting the clock drifts and the atmospheric zenith delays to the GROUP DELAY data. • Use the resulting model to estimate the phase ambiguities of the PHASE DELAY (pre-connection). • Refine the phase connection and perform the astrometric analysis (check the quality of the differential observables).

EPOCH 2000. 46, 15 GHz PHASE-CONNECTION -Time between obs. ~ 120 s -2 cycle at 15 GHz ~ 65 ps THUS, -Residual rates should be lower than 33 ps/120 ps ~ 0. 3 ps/s

Check Phase Closures Phase closures should be NULL for point-like sources, or for observables from which we extract all the source structure information.

Check Phase Closures Phase closures should be NULL for point-like sources, or for observables from which we extract all the source structure information.

Automatic Phase Connector The Algorithm: - For a given scan: • Finds which baseline appears more times in the set of non-zero closures. • Adds and subtracts 1 phase cycle to the delay of that baseline. Computes the score corresponding to each of these corrections: score = (# of closures moved closer to 0) – (# of closures moved away from zero). • The highest score will determine which correction is applied definitely. • Recomputes the closures and repeats the previous steps until all closures are zero. Applies the set of corrections found for the actual scan to the next scan, before it computes the closures of that new scan.

Automatic Phase Connector (Simulations) Corrected baselines: Baselines: Closures:

Antenna-based corrections:

Antenna-based corrections: Antenna: OV Source: 04 Nº of ambs: +1

The phase connection completed (undifferenced):

The phase connection completed (undifferenced):

The phase connection completed (differenced):

When things are not as expected. . .

When things are not as expected. . . Residual delay rate (ps/s) Baselines with SC Weather dependent. . .

When things are not as expected. . .

The phase connection completed (differenced):

Relative Position Uncertainty Triangles = RA uncertainties Squares = Dec uncertainties

Relative Position Uncertainty

Results: differential positions We find some large corrections of the relative sources coordinates with respect to the ICRF positions. Nevertheless, our astrometric results are not directly comparable to the ICRF: -Our astrometric corrections are defined with respect to the “phase centers” of the maps. Our astrometry considers, then, the structures of the sources. -Source opacity effects could be present while comparing the source positions observed at 15 GHz and 8. 4/2. 3 GHz -Mean corrections are: 278 as in RA 170 as in DEC

Some Results Astrometry of 0212+735 15 GHz

Some Results Astrometry of 0212+735 15 GHz 43 GHz

Some Results Astrometry of 1928+738

Some Results Astrometry of 1928+738 Ros et al. 2000

Some Results Astrometry of 1928+738 Ros et al. 2000

Results: 1928+738 time series 43 GHz 15. 4 GHz 8. 4 GHz X 1988. 83 Q 1999. 01 K 1999. 57 X 1991. 89 K 2000. 46 X 2001. 09 Q 2004. 62 X 2004. 53 C 1985. 8

Results: 1928+738 time series 43 GHz 15. 4 GHz 8. 4 GHz X 1988. 83 Q 1999. 01 K 1999. 57 X 1991. 89 K 2000. 46 X 2001. 09 Q 2004. 62 X 2004. 53 C 1985. 8

Results: 1928+738 time series 43 GHz 15. 4 GHz 8. 4 GHz X 1988. 83 Q 1999. 01 K 1999. 57 X 1991. 89 K 2000. 46 X 2001. 09 Q 2004. 62 X 2004. 53 C 1985. 8

Results: 1928+738 time series 43 GHz 15. 4 GHz 8. 4 GHz X 1988. 83 Q 1999. 01 K 1999. 57 X 1991. 89 K 2000. 46 X 2001. 09 Q 2004. 62 X 2004. 53 C 1985. 8

Results: 1928+738 time series 43 GHz 15. 4 GHz 8. 4 GHz X 1988. 83 Q 1999. 01 K 1999. 57 X 1991. 89 K 2000. 46 X 2001. 09 Q 2004. 62 X 2004. 53 C 1985. 8

Some results: opacity effects 8. 4/43 GHz astrometry for 1928+738 + 43 GHz + 8. 4 GHz + + 8. 4 GHz 43 GHz = - 0. 07 mas = 0. 45 mas

Some results: opacity effects 8. 4/43 GHz astrometry for 1803+784 + 43 GHz + 8. 4 GHz = 0. 23 mas = 0. 14 mas + 43 GHz

Conclusions • We have performed high-precision, wide-angle, astrometry analysis of a radio sample. • The phase delays have been well connected and we have checked the good quality of differenced delays in the astrometric fit. The use of these observables improves the accuracy of the astrometry by a factor of 2 -3 (the main source of uncertainties comes from the modeling of the tropospheric delay). We obtain differential astrometry precisions ranging from ~10 to ~500 mas (depending on source separations), which are ~10 times higher than the precisions achivevable with the phase-reference technique… • …But, at 15 and 43 GHz the success of the analysis depends much of the weather • Combination with other epochs provide precise kinematics (where’s the core? ) • Combination with other freqs provide precise spectral information