IRAS Explanatory Supplement
V. Data Reduction
E. Overview of Small Extended Source Data Processing
E.6 Band-Merging
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The weeks-confirmed, single-band sources were analyzed to see if they
could merge with weeks-confirmed sources in other bands to become multi-band
sources. Those sources in the four wavelength bands which positionally
confirmed were linked together. The sources were tested for positional
confirmation in the same way as in the cluster analysis processor, i.e.
two sources positionally confirmed if their link parameter,
2
as in Section V.E.5, was less than a certain threshold.
If all the single-band sources contributing to a band-merged source confirmed
with one another, then the source was said to be a mutually confirmed merger.
The information describing each band-merged source became the basis for the small extended source catalog. A full description of the contents of the catalog is given in Section X.C. Where two weeks-confirmed sources from one band competed to merge with a single source in another band the band-merging attempt was abandoned and the various single band components were listed separately in the catalog. A flag was set to indicate that the sources could not be successfully band-merged.
As an additional check on previous processing steps, the band-merging processor was allowed to look for possible band-mergers between weeks-confirmed sources from the same band. About 166 cases were found mostly 60 µm and 100 µm bands. Upon inspection, they were all found to occur in areas with at least four hours-confirming coverages, each of which had yielded an hours-confirmed detection. These four detections formed a pattern that generated two weeks-confirmed sources; the failure of all four to link together could be due to pointing errors, to scanning structures in different directions, or to artifacts of the processing. The two weeks confirmed sources obtained were naturally larger than the individual hours confirmed sources by a sufficient amount that the band-merging processor managed to link them.
All these cases of weeks-confirming candidates discovered too late were treated just like cases where several sources from the same band competed to band-merge with a single candidate from another band; the "band-merging" attempt was abandoned and the various single band components were listed in the catalog with the appropriate warning flag (see Section X.C).
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