Extended Source Confusion Flag: cc_flg
The XSC confusion flag, "cc_flg", indicates whether a source is identified as as artifact, associated with an artifact, associated with a large galaxy (a.k.a. "chaff"), derived from the Large Galaxy Atlas, or in fact an "inscan" duplicate. This flag is used to omit non-extended sources from the final catalog. The cc_flg is also tracked in the extended source working database.
cc_flg = "C" or to "D"
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DBMAPCOR identifies sources (point or extended) that are in close proximity to
bright stars. Two flavors: "C" indicates that the source fell within the "halo" of a
bright star; "D" indicates that the sources fell on top of a bright star diffraction source.
These "sources" are treated as artifacts and eliminated from the final XSC.
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The source is identified as an in-scan duplicate (coadd-to-coadd duplicates).
Dupes are defined to be sources within
5" radial proximity. The dupe marked with "I" is the one closest to an in-scan coadd edge
(and hence, least desirable of the dupe pair). These sources are eliminated from the final XSC.
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These sources are visually identified as artifacts, or "false-positives" (non-extended sources that make
it past the star-galaxy battery of discrimination tests). The vis identification for these sources
is, for the most part, serendipitous, and not done in any uniform complete fashion. Hence, these sources
remain in the final catalog even though we know they are bogus sources.
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These sources are visually identified as artifacts using uniform and (sqp-query) complete samples collected from
the extended source database. Several kinds of queries were carried out (see below), exploring the vast
parameter space that "artifacts" occupy in the extended source database. Since the queries were uniform/complete
and the vis identification is robust/reliable, these sources are eliminated from the final XSC.
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These sources are associated with very large galaxies. They tend to be "chaff"-like, in that
they are not discrete sources but are in fact pieces of the large parent galaxy (e.g., HII complex
on a spiral arm). This image shows M31/M32/M110 with "chaff" marked in green; the red
point at the center indicates a source that is within 4" of the nominal position of the LGA galaxies (see below).
These sources tend not to have reliable photometry due to the poor coadd background removal that arises from the large parent galaxy itself. These sources are identified and their photometry nulled from the XSC. An explanation of large galaxies is given here.
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These sources are large galaxies, whose positions and photometry are
derived from the
Large Galaxy
Atlas. These sources replace the pipeline measured sources (see
cc_flg="z" above) in the catalog.
-
Sources replaced in catalog by improved LGA measurements.
For the working database sourcs, cc_flg = "X" indicates that the
source is within 4 arcsec radius to a large (LGA) galaxy.
This image shows M31/M32/M110 with "chaff" marked in green; the red
point at the center indicates a source that is within 4" of the nominal position of the LGA galaxies.
[Last Updated: 2004 Aug 3; by Tom Jarrett]