APASS DR9 Best Neighbour (gaiadr3.apassdr9_best_neighbour)

The table has 74904004 rows, 7 columns.

Description

Table apassdr9_best_neighbour lists each matched Gaia object with its best neighbour in the external catalogue. The cross-match algorithm is not symmetric and searches Gaia sources counterparts in APASS DR9. The best neighbour is chosen among good neighbours as the one with the highest value of the figure of merit, which evaluates the ratio between two opposite models/hypotheses: the counterpart candidate is a match or it is found by chance. Good neighbours are nearby objects in the external catalogue whose position is compatible within position errors with the Gaia target. 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)

Attribution

If you have used Gaia data in your research, please use the following acknowledgement:

This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

More information can be found on the credit and citation instructions page.

Columns

Name Type UCD Unit Description
source_id long meta.id
meta.main
meta.ref

Unique Gaia source identifier

clean_apassdr9_oid long meta.id.cross

External Catalogue source identifier

original_ext_source_id long meta.id.cross

Original External Catalogue source identifier

angular_distance double pos.angDistance arcsec

Angular Distance between the two sources

number_of_neighbours integer meta.number

Number of neighbours in External Catalogue

number_of_mates short meta.number

Number of mates in Gaia Catalogue

xm_flag integer meta.code.status

Cross-match algorithm flag