III. 2MASS Overview

4. Caveats and Limitations of Sampler Products

b. Point Source Catalog Quality Flags

Important Notes to Users of the Point Source Catalog:

The origin and quality of the photometry listed in the "default" magnitude fields in the 2MASS Sampler Point Source Catalog is summarized in the "rd_flg", "cc_flg" and "bl_flg". It is essential that users refer to these flags when interpreting photometry for any source in the Catalog. Each one of these flags has three characters, each corresponding to one band: the first character is the J-band value, second is the H-band value, and third is the K_s value.

1. RD_FLG (Read Flag)
   Indicates whether the source was detected in each of the three bands, and describes the source of the magnitude and uncertainties.

Value	Source of Photometry
0	Not Detected In That Band - Quoted Magnitude is a 95% Confidence Upper Limit
1	R1 Aperture Photometry
2	R2-R1 Profile-Fit Photometry
3	Saturated in R1 - Photometry estimated from First Persistence Artifact - Extremely Uncertain!
4	R2-R1 Aperture Photometry - Extremely Uncertain!
8	Very bright star - Photometry and Position provided from External Catalogs for Informational Purposes Only

2. BL_FLG (Blend Flag)
   Indicates the number of components fit simultaneously in profile fit photometry. A measure of source density and possible confusion

Value	Interpretation
0	Source not detected in that band
1	Single profile fit to isolated source
>1	Multiple sources detected in small region and fit simultaneously. Value indicates the number of components fit

3. CC_FLG (Contamination and Confusion Flag)
   Describes if source measurement may be affected by bright star artifacts such as diffraction spikes, persistence images, stripes or ghost images, or if measurements source is confused due to proximity to bright stars or other nearby objects.

Value	Nature of Artifact or Confusion
0	Source is unaffected by artifacts, or source not detected in that band
P	Persistence Image from Bright Star
D	Nearby Diffraction Spike
S	Horizontal "Stripe" due to Bright Star
R	Internal Reflection due to Bright Star
C	Confusion with nearby source
B	Confusion in Bandmerging