What are the basic parameters used to construct the source lists?
For the DAOPHOT source lists, circular aperture photometry is performed with radii of 1 and 3 pixels. The background is defined as the median in annulus from 5 to 10 pixels. A concentration index (CI) is defined as the difference between the magnitudes in the 1 and 3 pixel radii. This is used to define a flag value, which is 0 for point sources and 1 for extended sources. Aperture corrections for stellar sources are added to the point sources to estimate a total magnitude. For extended sources a value of 999. or -999. is placed in the total magnitude column. The information above, plus other useful information is included in the header of each source list. For SExtractor source lists, we use the base set of parameters used to construct the catalogs for the Ultra Deep Field (UDF) with minor deviations, available at http://archive.stsci.edu/prepds/udf/udf_hlsp.html.
