Cross Matcher tool for Multiple catalogues

Task Name CrossMatcher (Full)

Summary

Target VOTable and Match VOTable can be URLs or inserted from MySpace. If doing this manually, after inserting each Match VOTable a box will appear for the next one until you leave the last one blank. If you are running this from a script you can enter a list of multiple Match VOTable s separated by ++ .

The units of Maximum search radius and Match Radius are arcsec.

Description

Sources in a Target VOTable catalogue are matched with sources in one or more Match VOTable catalogues if a target source is within Maximum search radius of the matches position.

If more than one Match VOTable catalogue is specified then, if a pair of target-matched sources from separate matches catalogues are within Match Radius they are reported as a double match (and so on for triple matches etc.). Sources are only passed if they lie within Maximum search radius of a target source, inter-matches-catalogues matching is not sufficient.

Any relevant astrometric uncertainties should be included in Maximum search radius and Match Radius .

If you are importing catalogues which may not conform to AstroGrid standards, please see Further Information below.

Examples

Example 1
Target VOTables contains a catalogue of clusters of galaxies, maximum cluster radius 60", which is entered as Maximum search radius. Match VOTable lists 3 catalogues of individual galaxy positions in radio, optical and x-ray catalogues; the emission might come from different positions within the same galaxy. The position uncertainties and possible galaxy extents combine to give a Match Radius of 5". Thus the result might contain:

Example 2
Target VOTables contains an extract from the 2MASS catalogue and Match VOTable lists two optical catalogues covering the same region. The interesting sources are stars which should be point-like and exactly aligned apart from the respective PSFs and astrometric errors, which amount to 5" for 2MASS and 1.5" for each optical catalogue. The combined uncertainties are then approximately Maximum search radius = 5" for matches with 2MASS, and Match Radius = 2" for optical source matches.

• Further information (correct as of April 2005):
  • The input catalogues must be in VOTable format e.g. as produced by AstroGrid SExtractor. See WhatIsAVOTable for more information.
  • All data are assumed to be in the same, equatorial, celestial coordinate system; there is no provision for conversion between e.g. B1950 and J2000
  • The input catalogues must contain the correct and unique UCDs (POS_EQ_RA_MAIN, POS_EQ_DEC_MAIN) for positions in either decimal degrees (DDD.DDD +ddd.dd) or hexadecimal (HH MM SS.SSS +dd mm ss.ss or HH:MM:SS.SSS +dd:mm:ss.ss). + is optional for positive declinations.

• Future developments will include
  • Selection of units by user
  • Specification of minimum search radius
  • Specification of max. and min. numbers of matches
  • Use of errors from catalogue columns in matching
  • Matching on user-selected columns

Tool written by PatricioOrtiz

-- AnitaRichards - 14 Mar 2005