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

Dusty star-forming galaxies (DSFGs) play a major role in the overall star formation in the Universe at high redshift. While deep near-infrared surveys, particularly with JWST, can now identify many heavily obscured galaxies, (sub)millimeter observations are essential for measuring their dust emission and quantifying their dust content and obscured star formation. We present the final 1.2,mm and 2,mm source catalogs and the redshift distribution of the millimeter-selected population from the NIKA2 Cosmological Legacy Survey (N2CLS) in the COSMOS field. Our aim was to provide a comprehensive dataset for studying the physical properties and evolution of high-redshift DSFGs and to compare the observed redshift distribution with theoretical predictions. We analyzed deep NIKA2 observations at 1.2,mm and 2,mm, covering ∼1070,arcmin2$ with median noise levels of 315,mathrm μJy and 91,mathrm μJy, respectively. Sources were extracted with a signal-to-noise ratio (S/N) threshold of 3.9, ensuring ≥80% purity. We identified multiwavelength counterparts using high-resolution interferometric (sub)millimeter data (NOEMA, ALMA) and radio observations (VLA, MeerKAT). Redshifts were compiled from spectroscopic and photometric catalogs (e.g., COSMOSWeb). We compared the redshift distribution to predictions from the SIDES simulations and other galaxy evolution models (e.g., SHARK and FLAMINGO). The N2CLS master catalog includes 323 sources detected at ≥80% purity, with 104 sources detected in both bands, 197 only at 1.2,mm, and 22 only at 2,mm. Multiwavelength identifications were secured for ∼89% of the sample. The redshift distribution of 1.2,mm high-purity (geq95%) sources peaks at $2.8 ± 0.1, consistent with the epoch of peak cosmic star formation. In the total sample, we lack redshifts for sim2% of the identified galaxies plus 34 sources for which no accurate positional proxy is available, preventing the identification of a multiwavelength counterpart. We identified 66 galaxies at z > 4 (19 with spectroscopic redshifts). The observed redshift distribution agrees well with the SIDES simulations, while four other galaxy evolution models are statistically inconsistent with the data. Using NIKA2 at the IRAM 30,m telescope, we conducted N2CLS, the largest contiguous deep millimeter survey to date at this depth with homogeneous coverage. This homogeneous coverage is important, as 25% of N2CLS sources lack a SCUBA2 850,̊m μ m counterpart, likely because the strongly nonuniform noise distribution of the SCUBA2 map results in lower sensitivity in parts of the field. The released data products, including maps, catalogs, and multiwavelength identifications, provide a legacy dataset for studying dust-obscured galaxy evolution. The N2CLS bridges wide-area single-dish observations and high-resolution interferometric studies, enabling future investigations into the physical properties and cosmic evolution of DSFGs.