q_identify_srcs

q_identify_src calculates the distance between each pair consisting of an expected catalogue source and a source found in the FOV by the ISSW. This distance and the error radii of the sources are used to calculate the relative distance, . It is therefore essential that the quoted position error has a meaningful value. The relative distances are then stored in an array. Two new arrays are then created one ranking each catalogue source with relDist (the largest value of relative distance considered when matching sources) for its proximity to each found source, and the other ranking each found source with relDist for its proximity to each catalogue source. These two arrays are compared and five classes of source matches are found:

• Good matches: The found and catalogue source are the best fit to each other alone (relative distance between the match sources is much less than 1.
• Confused Sources: Two found sources are equally good fits to a particular catalogue source (within the slackness allowed by distFuzz,i.e., fractional difference in two relative distances that can be considered insignificant when making a match, and relDist) - one of them could be a new source.
• Multiple Identification: One found source can be equally well identified with two (or more) catalogue sources (within the slackness allowed by distFuzz and relDist).

• New Source: A found source that cannot be matched to any catalogue source.
• Not Found Source: A catalogue source that couldn't be matched to any of the found sources.

  In the case of the two ambiguous categories (Multiple and Confused) the program makes no attempt to separate sources further or resolve conflicts between various possible matches - this should be done by a human. More details on the format of the output result is given in Appendix C.6.2.

Table 16: q_identify_srcs parameters included into the main script

Name	Type	Description
IMA_relDist	real	This is a parameter that sets the allowed separation between CAT-sources and RES-sources that are to be considered as the 'same'. relDist is calculated from:relDist=d/ . Here d is a distance between the sources and and are the error radii. default: 1.5
IMA_fluxLimit	real	Lower flux limit for alerts of unfound sources [Counts/cm/s ]. default: 0.0
IMA_searchRad	real	Range of search grid (in degrees) around nominal found source positions default: 0.25
IMA_gridNum	integer	Number of grid steps on one side of search grid default: 25
IMA_distFuzz	real	Fractional difference in the relative distance of two found sources that allows them still to be considered equally good fits for a catalogue source. default: 0.15