CHAMPS: Data Reduction and Detection of 3300 Dusty Galaxies at 1.2 mm

We present the reduction and source catalogs for the COSMOS High- z ALMA-MIRI Population Survey (CHAMPS), the largest Atacama Large (Sub)Millimeter Array (ALMA) blank field survey to date at 0.2,deg squared. With observing frequency centered at 250, GHz (1.2, mm) and bandwidth of 7.5 GHz, CHAMPS covers the JWST/NIRCam+MIRI footprint in the COSMOS field, taking advantage of the rich, multiwavelength ancillary datasets in COSMOS ranging from X-ray to radio. The majority of the CHAMPS survey (90 %) has depths at or below 200 μ Jy beam-1 and with an average RMS of 146 μ Jy beam-1. The reduced CHAMPS mosaic has a beam size of θ res = 1.1'' times 1.1''. CHAMPS identifies sources via two detection methods, a blind search for high-SNR sources, and a prior-based search involving MIRI detections to identify faint sources. The blind search yields a total of 595 sources down to an SNR 4.5σ while the prior catalog yields a total of 3162 source down to an SNR 3σ, leading to a full sample of 3355 unique objects detected across both catalogs. We identify a unique population of 385 SNR 5σ sources across the two catalogs; after excluding 9 likely spurious edge detections we define a robust science sample of 376 sources above 5σ. These sources have a median redshift of z 1.2 mm = 2.54+0.89-1.69 based on optical/near-IR/mid-IR photometric redshifts and high-quality spectroscopic redshifts, and hold a median stellar mass of (M/M) = 10.79+0.42-3.08. We have further identified 68/376 (about18%) sources as candidate AGN through X-ray, UV-optical, infrared and radio selection techniques.