2MASS Extended Source Catalog: Overview and Algorithms

The 2 Micron All-Sky Survey (2MASS) will observe over one-million galaxies and extended Galactic sources covering the entire sky at wavelengths between 1 and 2 microns. The survey catalog will have both high completeness and reliability down to J = 15.0 and Ks = 13.5 mag, equivalent to 1.6 mJy and 2.9 mJy, respectively. This paper describes the basic algorithms used to detect and characterize extended sources in the 2MASS database and catalog. Critical procedures include tracking the point spread function, image background removal, artifact removal, photometry and basic parameterization, star-galaxy discrimination and object classification using a decision tree technique. Examples of extended sources encountered in 2MASS are given.