2025RNAAS...9...52M

We report the detection of [C I] ³P₁-³P₀ emission in the nearby galaxy NGC 7679 using the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array (ALMA). In T. Michiyama et al., [C I] ³P₁-³P₀ emission in NGC 7679 was reported as undetected based on ACA observations conducted in 2019 (ALMA Cycle 6). These observations had ∼1 minute on-source time and used a single pointing with a field of view (FoV) of ∼20″. In 2023 (Cycle 9), we carried out mosaic observations using seven pointings with an FoV of ∼27″ and 4-5 minutes on-source per pointing. The additional data have significantly improved the line sensitivity, uv-sampling, and noise uniformity across the galaxy disk. Our Cycle 9 observations confirm the presence of extended [C I] ³P₁-³P₀ emissions in NGC 7679, which was completely missed in the Cycle 6 observations due to insufficient sensitivity and uv-sampling. This highlights the basic technical challenges of estimating the total flux by interferometric observations with sparse uv sampling.