Visual Inspection of Extended Sources

Over the course of the 2MASS project, extended sources have been visually inspected during spot checks and systematic checks of completeness and reliability. The inspection consists of viewing a J+H+Ks RGB color-combined image, tabular data (sizes and photometry), and (when available) an optical DSS image. The images are viewed with both linear and logarithmic stretches to inspect both high and low surface brightness features.

a. Visual Classification

About 600,000 total sources have been inspected and classified (see code below). Roughly 25-30% of all XSC sources have been inspected, with close to 100% inspected at the bright end (Ks < 12.5 mag). The XSC includes a visual inspection flag "vc" that encodes the following classification:

The GALWORKS star/galaxy discrimination techniques were developed to maximized galaxies and galactic fuzz (vc = 1), and to minimize contamination from stars, artifacts, doubles and triples (vc = 2).

b. Gallery of Sources

The following is a very brief gallery of some sources encountered by 2MASS.

Galaxy vc = 1, cc_flg = 0

Star vc = 2, cc_flg = 0

Unknown vc = -2, cc_flg = 0

Artifact vc = 2, cc_flg = A

Double Star vc = 2, cc_flg = 0

Galactic Fuzz vc = 1, cc_flg = 0

Triple Source vc = 2, cc_flg = 0

[Last Updated: 2002 Aug 16; by Tom Jarrett]