The NIKA2 Cosmological Legacy Survey in COSMOS: Final 1.2mm and 2mm source catalogs and redshift distribution of dusty star-forming galaxies

Abstract

We present the final 1.2mm and 2mm source catalogs and the redshift distribution of the mm-selected population from the NIKA2 Cosmological Legacy Survey (N2CLS) in the COSMOS field. Our aim is to provide a comprehensive dataset for studying the physical properties and evolution of high-redshift DSFGs. N2CLS covers ~1070 arcmin2 with median noise levels of 315$\mu$Jy and 91$\mu$Jy at 1.2 and 2mm, respectively. Sources are extracted with a S/N threshold of 3.9, ensuring >80% purity. Multi-wavelength counterparts are identified using high-resolution interferometric (sub-)mm data (NOEMA, ALMA) and radio observations (VLA, MeerKAT). Redshifts are compiled from spectroscopic and photometric catalogs (e.g., COSMOSWeb). The N2CLS master catalog includes 323 sources detected at >80% purity, with 104 sources detected in both bands, 197 only at 1.2mm, and 22 only at 2mm. Multi-wavelength identifications are secured for ~89% of the sample. The redshift distribution of 1.2mm sources peaks at 2.8$\pm$0.1, consistent with the epoch of peak cosmic star formation. In the total sample, we lack redshift for ~2% of the identified galaxies, plus 34 sources for which no accurate positional proxy is available, preventing the identification of a multi-wavelength counterpart. We identify 66 galaxies at z>4. The observed redshift distribution agrees well with the SIDES simulations, while four other galaxy evolution models are statistically inconsistent with the data. N2CLS is the largest contiguous deep survey to date with this depth and homogeneous coverage. This homogeneous coverage is important, as 25% of N2CLS sources lack a SCUBA2 850 mic counterpart, likely because the strongly non-uniform noise distribution of the SCUBA2 map results in lower sensitivity in parts of the field.The released data products provide a legacy dataset for studying dust-obscured galaxy evolution.