The unWISE Catalog: Two Billion Infrared Sources from Five Years of <i>WISE</i> Imaging

We introduce the unWISE Catalog, containing the positions and fluxes of roughly 2 billion objects observed by the Wide-field Infrared Survey Explorer (WISE) over the full sky. The unWISE Catalog has two advantages over the existing WISE catalog (AllWISE): first, it is based on increasingly deeper imaging, and second, it features improved modeling of crowded regions. The deeper imaging used in the unWISE Catalog comes from the coaddition of all publicly available 3–5 μm WISE imaging, including that from the ongoing NEOWISE-reactivation mission, thus increasing the total exposure time by a factor of 5 relative to AllWISE. At these depths, even at high Galactic latitudes, many sources are blended with their neighbors; accordingly, the unWISE analysis simultaneously fits thousands of sources to obtain accurate photometry. Our new catalog detects sources roughly 0.7 magnitudes fainter than the AllWISE catalog at 5σ, and more accurately models millions of faint sources in the Galactic plane, enabling a wealth of Galactic and extragalactic science. In particular, relative to AllWISE, unWISE doubles the number of galaxies detected between redshifts 0 and 1 and triples the number between redshifts 1 and 2, cataloging more than half a billion galaxies over the whole sky.