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arXiv · 2503.09913

From Non-Detection to Detection: Atacama Compact Array Mosaic Observations of Faint Extended [C I] Emission in NGC 7679

Tomonari Michiyama·Toshiki Saito·Kouichiro Nakanishi·Daisuke Iono·Ken-ichi Tadaki·Juan Molina·Bumhyun Lee·Ming-Yang Zhuang·Junko Ueda·Takuma Izumi·Luis C. Ho
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Abstract

We report the detection of [C I] $^3P_1$--$^3P_0$ emission in the nearby galaxy NGC 7679 using the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array (ALMA). In Michiyama et al. (2021), [C I] $^3P_1$--$^3P_0$ 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 arcsec. In 2023 (Cycle 9), we carried out mosaic observations using seven pointings with an FoV of ~27 arcsec 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] $^3P_1$--$^3P_0$ emission 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.

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Tomonari Michiyama, Toshiki Saito, Kouichiro Nakanishi, Daisuke Iono, Ken-ichi Tadaki, Juan Molina, Bumhyun Lee, Ming-Yang Zhuang, Junko Ueda, Takuma Izumi, Luis C. Ho. 2025-03-13. From Non-Detection to Detection: Atacama Compact Array Mosaic Observations of Faint Extended [C I] Emission in NGC 7679. https://doi.org/10.3847/2515-5172%2Fadbc9b

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