Description of Point Source Photometry Steps Used by GLIMPSE

The Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE) is an infrared survey of the inner Galactic plane using the Infrared Array Camera (IRAC) (Fazio et al. 2004) on board the Spitzer Space Telescope (SST) (Werner et al. 2004). IRAC has four detectors, centered at approximately 3.6, 4.5, 5.8 and 8.0 μm. GLIMPSE covered a latitude range of ±1◦, and a longitude range of |l| =10◦−65◦ (Benjamin et al. 2003). The GLIMPSE data products consist of a Point Source Catalog (GLMC), Point Source Archive (GLMA) and 1.1◦×0.8◦and 3.1◦×2.4◦ mosaic images covering the survey area. See the GLIMPSE Data Products Document at www.astro.wisc.edu/glimpse/docs.html for more information. We use the DAOPHOT package (Stetson 1987) for point source photometry, modified to work with highly variable backgrounds. This document describes the steps used to produce the photometry for the GLIMPSE source lists. The GLIMPSE Quality Assurance Document (www.astro.wisc.edu/glimpse/docs.html) discusses the photometric accuracy along with other issues affecting data quality.