Working Database DB_MAPCOR Point Source Results

Introduction

MAPCOR, working on one band of one scan at a time, can find bright star artifacts that are limited to the scan in which the star appears, namely persistence and filter and dichroic glints; DB_MAPCOR deals with the artifacts that are not limited to the same scan and thus require a database search. DB_MAPCOR searched for point sources in the Working Database (WDB) but not the ADR catalog generation database that are photometrically contaminated by flux from other nearby stars (photometric confusion), artifacts caused by very bright stars (artifact confusion), point sources contaminated by diffraction spikes, and artifacts caused by diffraction spikes. (For more information on the search algorithms, see the  Artifact Identification Algorithms and Parameters page.)

Parent Source Lists

A few sources in the correct magnitude range are found in the PSC but not the original DB_MAPCOR parent list: 7 in or near the southern hemisphere, 5 of which were also in or near the northern. They were all victims of missed band- or frame-merges earlier in the pipeline and many were in close multiple systems; I added them to the list, after band-merging by hand where necessary. Please see the ADR catalog generation  DB_MAPCOR Point Source Results page for further information on the original DB_MAPCOR parent list.

As before, DB_MAPCOR was only run on the parent sources with J, H, or K_s magnitudes <= 6.0. This now includes a total of 95534 parents for the northern hemisphere and 159033 for the southern hemisphere, not counting duplicate source apparitions. However, DB_MAPCOR skips parents without valid detections in at least two bands. (For details, see  Single-Band Parents Skipped.) This removed 19 parents from consideration for the north and 23 for the south, leaving 95515 parents for the north and 159010 for the south. Of these parents, 155076 caused new artifact flags in the J band, 157913 in the H band, and 156057 in the K_s band.

Possible Artifact Flag Values

DB_MAPCOR will never lessen the severity of a flag already set by MAPCOR; however, it can add different artifact flags to sources already flagged, so some of the sources with new flags were already marked as artifacts.

One 3-character flag for each band, called j_prg_flg, h_prg_flg, and k_prg_flg, contains complete artifact flag information for each band in numerical codes. DB_MAPCOR can update these flags with the following values (``?'' means any single character, as in csh wildcards):

• ``?5?'' indicates that the source is bright enough to be accepted as a real source but is contaminated by a diffraction spike.
• ``?6?'' indicates that the source is likely part of a diffraction spike.
• ``??1'' indicates that the source is found within the photometric confusion radius of a parent source.
• ``??2'' indicates that the source is found within the artifact confusion radius of a parent source and is likely false.

After the [jhk]_prg_flg flags are set by both MAPCOR and DB_MAPCOR, the fourth 3-character flag, cc_flg, combines all the possible artifact and contamination values into a one-character code for each band. To set this flag, the [jhk]_prg_flg and persistence probability values for each band are checked in the order given below until a value is applied. This means that possible flag values further down this list will not be applied if a flag found above it is already set; in other words, the order indicates the flag hierarchy.

The cc_flg characters for each band can be:

• `P': Persistence probability ?_prob_pers > 0.5.
• `G': Source is positionally associated with a filter glint. (?_prg_flg = ``1??'')
• `C': Confusion Artifact. Source is likely a spurious detection of the confusion halo around a bright star. (?_prg_flg = ``??2'')
• `D': Diffraction Spike Artifact. Source is likely a detection of a diffraction spike from a nearby bright star. (?_prg_flg = ``?6?'')
• `p': Persistence probability 0.1 < ?_prob_pers <= 0.5.
• `c': Photometric Confusion. Source has biased photometry due to proximity to a bright star that causes an incorrect measurement of the background. (?_prg_flg = ``??1'')
• `d': Real source that is affected by proximity to a diffraction spike from a nearby star. (?_prg_flg = ``?5?'')
• `s': Source is likely a detection of or affected by a NICMOS3 ``stripe'' from a bright star at delta_y = 0, 256, -256 arcsec. (?_prg_flg = ``??1'')
• `b': Bandmerge confusion -- more than one bandmerge candidate. (cnf_flg for that band is >1 in either the first or second digit)
• `0': Source is unaffected by artifacts, or is not detected in that band. (?_prg_flg = ``000'' or ``fil'' or ``upl'')

The capital letters indicate that MAPCOR or DB_MAPCOR determined that the source was an artifact in that particular band; lower case letters indicate that the source is likely real but contaminated by an artifact in that band. The flag values DB_MAPCOR can set are 'C', 'D', 'c', and 'd'; all others are set by MAPCOR or other subsystems.

Artifact Flag Results

After DB_MAPCOR sets new artifact flag values, another program merges those values with those already found in the working tables so that no information is overwritten unnecessarily. This has not yet been done, so the following flag counts are only those that DB_MAPCOR has set. The full list of these counts can be found in  this page. Summary tables of the new values set by DB_MAPCOR, affecting 527063 point sources, are below.