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

Abstract

We present the reduction and source catalogs for the \textit{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${}^2$. 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 $\mu$Jy beam${}^{-1}$ and with an average RMS of 146 $\mu$Jy beam${}^{-1}$. The reduced CHAMPS mosaic has a beam size of ${\theta }_{\mathrm{res}}=1.1^{\prime \prime }\times 1.1^{\prime \prime }$. 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 $\ge 4.5\sigma$ while the prior catalog yields a total of 3162 source down to an SNR $\ge 3\sigma$, leading to a full sample of 3355 unique objects detected across both catalogs. We identify a unique population of 385 SNR $\ge 5\sigma$ sources across the two catalogs; after excluding 9 likely spurious edge detections we define a robust science sample of 376 sources above $\ge 5\sigma$. These sources have a median redshift of $⟨z_{1.2\text{ mm}}⟩=2.54_{-1.69}^{+0.89}$ based on optical/near-IR/mid-IR photometric redshifts and high-quality spectroscopic redshifts, and hold a median stellar mass of $⟨\log ({\mathrm{M}}_{\star }/{\mathrm{M}}_{\odot })⟩=10.79_{-3.08}^{+0.42}$. We have further identified 68/376 ($\sim 18\%$) sources as candidate AGN through X-ray, UV-optical, infrared and radio selection techniques.