14.5.8 hipparcos2_neighbourhood

Hipparcos-2 Neighbourhood table includes all good neighbours for each matched external catalogue object. A good neighbour for a given external catalogue object is a nearby object in Gaia whose position is compatible (within position errors) with the target.

Columns description:

source_id : Unique Gaia source identifier (long)

Unique identifier of the Gaia source, the attribute corresponds to gaia_source.source_id

original_ext_source_id : Original External Catalogue source identifier (long)

The unique source identifier in the original External catalogue.

angular_distance : Angular Distance between the two sources (double, Angle[arcsec])

Angular distance between a Gaia source and its good neighbours in the External Catalogue

score : Score of neighbours (double)

The score is a figure of merit based on geometric distance and local density of the external catalogue: the higher the score, the more probable the match is.

gaia_astrometric_params : Number of Gaia astrometric params used (short)

This field indicates the number of Gaia astrometric parameters which were available in Gaia.
The field is set to 2 when only RA and DEC where available, while is set to 5 when RA, DEC, PMRA, PMDEC and PARALLAX are available and thus used to propagate a Gaia source position to the External Catalogue source coordinates epoch.