IV. 2MASS Data Processing
5. Extended Source Identification and Photometry
iii. 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
Atlas, or in fact an "inscan" duplicate.
This flag is used to omit non-extended sources from the final catalog.
cc_flg = "C" or to "D"
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.
cc_flg = "I"
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.
cc_flg = "a"
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.
cc_flg = "A"
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.
cc_flg = "z"
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). 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
cc_flg = "Z"
These sources are large galaxies, whose positions and photometry are
derived from the
Atlas. These sources replace the pipeline measured sources (see
cc_flg="z" above) in the catalog.
[Last Updated: 2002 Jul 16; by T. Jarrett]
Return to Section IV.5a.