SkyMapper DR2 Neighbourhood

Table <code>skymapperdr2_neighbourhood</code> includes all good neighbours for each matched Gaia object. A good neighbour for a given Gaia source is a nearby object in the external catalogue whose position is compatible (within position errors) with the Gaia target. The cross-match algorithm is not symmetric and searches Gaia sources counterparts in SkyMapper DR2. The cross-match algorithm is positional and exploits the full 5 parameter covariance matrix of the Gaia astrometric solution when available and the external catalogue positions and position errors. In addition it takes into account the external catalogue environment using the local density.
Please note that the cross-match algorithm is a trade-off between multiple requirements, in particular between completeness and correctness. It is thus not limited to a simple cone search.
Reference papers:Marrese et al. (2017)Marrese et al. (2019)