Table 2
Global differences between the Gaia DR1 positions of ICRF sources and their positions in ICRF2, expressed by the orientation and glide parameters.
| Rotation | Glide | |||||||||
| Source selection | Weighting | N | x | y | z | x | y | z | ||
|
|
||||||||||
| All with ρ< 5 mas | no | 1884 | 0.00 ± 0.04 | 0.03 ± 0.04 | 0.01 ± 0.04 | 0.00 ± 0.04 | −0.11 ± 0.04 | −0.05 ± 0.04 | ||
| all with ρ< 10 mas | no | 2054 | −0.03 ± 0.06 | 0.02 ± 0.06 | 0.00 ± 0.05 | −0.02 ± 0.06 | −0.08 ± 0.06 | −0.10 ± 0.05 | ||
| All | yes | 2191 | 0.02 ± 0.05 | 0.06 ± 0.04 | 0.04 ± 0.05 | 0.01 ± 0.05 | −0.08 ± 0.05 | −0.13 ± 0.05 | ||
| All in region A | yes | 1982 | 0.03 ± 0.02 | 0.03 ± 0.02 | 0.01 ± 0.02 | 0.01 ± 0.02 | −0.07 ± 0.02 | −0.11 ± 0.02 | ||
| Defining | yes | 262 | 0.00 ± 0.08 | 0.04 ± 0.07 | 0.01 ± 0.08 | −0.04 ± 0.07 | −0.14 ± 0.07 | −0.07 ± 0.07 | ||
| Defining in region A | yes | 247 | 0.01 ± 0.04 | 0.01 ± 0.03 | 0.03 ± 0.04 | −0.01 ± 0.04 | −0.12 ± 0.04 | −0.12 ± 0.04 | ||
Notes. All numbers are in mas and the VSH analysis was done with lmax = 5. ρ is the angular separation between the optical and radio positions. Region A is defined in Sect. 4.3 (see Fig. 13). The weighted solutions use a non-diagonal weight matrix resulting from the combination of Gaia and ICRF2 covariances. In this way a quadratic combination of Gaia and ICRF2 uncertainties is considered, and also the effective correlation given by Eq. (5). If the correlation is neglected, the estimates are typically shifted by a half of the corresponding uncertainty. N is the number of sources used in the solution. The columns headed x, y, z give the components of the rotation and glide along the principal axes of the ICRS.
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