Data Release 4 (DR4)

Data Release 4 (DR4) contains the complete, reduced GPIPS data set. All data products in DR4 are described in Clemens et al. (2020).

Overview: GPIPS was performed as observations of a 9×9 arcmin grid across Galactic longitudes 18 – 56 degrees and Galactic latitudes -1 to +1 degree. Each observation used the 10×10 arcmin field of view (FOV) of the Mimir instrument. Each observation consisted of 6 (or 7) distinct sky pointings (dithers), offset by about 15-18 arcsec from each other. At each pointing, the Mimir instrument was used to collect 16 (or 17) images, each through a distinct orientation of the cold, half-wave plate prior to analysis by a cold, fixed wire grid and detection by the 1024×1024 array detector.

As a result, there are 3,237 different sky fields (FOVs) comprising GPIPS and the DR4 data products fall into two main branches: FOV-based and unique star based.

In common to both branches is the GPIPS Field Properties Summary Table, which lists information about each sky field observed, the hand-written observing logs, and the GPIPS Release Notes file that contains update information and suggestions.

The FOV-based data products include, for each of the sky fields: a deep photometric image (in FITS format); a catalog of stellar photometry of all stars in a field (a PHOTCAT); a catalog of stellar polarimetry (a POLCAT); a DS9 overlay (region) file for the deep photometric image; and a printable image of the field, with overlay (in PS and PDF formats). In addition, for the FOV-based release, there are archival catalog matching files for Gaia DR2, 2MASS, GLIMPSE (Spitzer/IRAC), and WISE stars that match to GPIPS stars, and that do not match to GPIPS stars.

The unique star based DR4 release consists of a single file of resolved stellar duplicates with archival catalog match key data fields.