Preview of VLBI/Gaia Data Release 2 differences

On 2018.04.25 Gaia DR1 catalogue of 1,692,919,135 objects was released. The data are accessible here, 1.3 Tb after uncompressing.

There are 8801 matching sources between VLBI RFC 2018a source position catalogue and Gaia DR2.

VLBI and Gaia DR2 errors

Gaia DR2 position errors are smaller than position errors of 8801 matching VLBI sources.

 

Here is the raw distirbution of 8801 normalized arc lengths. The arc lengths were divided by their formal uncertainties computed using reported VLBI and Gaia DR2 uncertainties and the correlation between right ascension and declination.

Here VLBI position uncertainties were scaled by 1.25 factor. The distribution was transformed using the power low D(x) = d(x)λ with parameter λ=0.8. The distribution is reconciled with the Rayleighian, if either VLBI position uncertainties are scaled by 1.25 factor or Gaia DR2 position are scaled by 1.4.

Distribution of VLBI and Gaia DR2 offset directions

It was found ( Kovalev et al.(2017); Petrov, Kovalev (2017a); Petrov, Kovalev (2017b) ) that Gaia DR1 minus VLBI offsets directions with respect to parsec-scale jet direction show a strong anisotropy. This anisotropy was interpreted as manifestation of optical jets at scales 1–200 mas that cannot be observed directly. It was predicted that the anisotropy will be sharper for Gaia DR2 minus VLBI. This prediction has been confirmed!

Here is the table of the distribution of position angles of Gaia DR2 minus VLBI offsets with respect to jet directions at parsec scales found from analysis of VLBI images. Only those matches for which jet directions were reliably identified were used for producing these distributions.

All matches in a range 0 to 200 mas
Gaia DR2 Gaia DR1
Matches in a range 0 to 200 mas with σ > 2
Gaia DR2 Gaia DR1
Matches in a range 10 to 200 mas with σ > 4
Gaia DR2 Gaia DR1
Matches in a range 3 to 10 mas with σ > 2
Gaia DR2 Gaia DR1
Matches in a range 2 to 3 mas with σ > 2
Gaia DR2 Gaia DR1
Matches in a range 1 to 2 mas with σ > 2
Gaia DR2 Gaia DR1
Matches in a range 0 to 1 mas with σ > 2
Gaia DR2 Gaia DR1

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Last update: 2018.05.09_18:24:17
Web page was prepared by Leonid Petrov ()