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arXiv · 2606.10557

Molecular Gas Structure and Star Formation Diversity in Stephan's Quintet Revealed by ACA CO(1-0) Mapping

Misaki Yamamoto·Fumiya Maeda·Kazuyuki Muraoka·Fumi Egusa·Shinya Komugi·Bunyo Hatsukade·Hiroyuki Kaneko·Masato I. N. Kobayashi·Kotaro Kohno·Ayu Konishi·Kana Morokuma-Matsui·Kouichiro Nakanishi·Kouji Ohta
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Abstract

We present $^{12}$CO(1-0) mapping across the entire system of Stephan's Quintet, a well-known compact galaxy group, observed by Atacama Compact Array (7\,m array + Total Power) of the Atacama Large Millimeter/submillimeter Array. These observations provide the first large-scale ($137\,\mathrm{kpc}\times119\,\mathrm{kpc}$), spatially resolved ($\sim$5.5\,$\mathrm{kpc}$) molecular gas map of a compact group. Our CO map revealed that most of the molecular gas resides in the disk of the member galaxy NGC~7319 and in the intergalactic regions, including components along the shocked filament and the optically identified tidal tail extending from NGC~7319. Along the tidal tail and its surroundings, we found not only an extended molecular gas component but also four discrete CO clumps, with velocity dispersions of $\sim$10-30 $\mathrm{km\,s^{-1}}$ and molecular gas masses of order $10^7$-$10^8\,M_\odot$. Three of these clumps spatially overlap with H\,{\sc i}, whereas the remaining clump shows no associated H\,{\sc i} or counterparts at optical and infrared wavelengths. Using star formation rates derived from H$\alpha$ luminosities of H\,{\sc ii} regions, we found that star formation efficiencies (SFEs) span $\sim$2.2\,dex ($\sim$0.02--4\,Gyr$^{-1}$) and negatively correlate with CO velocity dispersion. While regions with small velocity dispersion exhibit SFEs comparable to those of nearby disk galaxies, those with large velocity dispersion ($\sim$50-150$\,\mathrm{km\,s^{-1}}$) around the shocked filament show strongly suppressed star formation. These results suggest that turbulence plays a significant role in regulating star formation in interacting systems.

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Misaki Yamamoto, Fumiya Maeda, Kazuyuki Muraoka, Fumi Egusa, Shinya Komugi, Bunyo Hatsukade, Hiroyuki Kaneko, Masato I. N. Kobayashi, Kotaro Kohno, Ayu Konishi, Kana Morokuma-Matsui, Kouichiro Nakanishi, Kouji Ohta. 2026-06-09. Molecular Gas Structure and Star Formation Diversity in Stephan's Quintet Revealed by ACA CO(1-0) Mapping. https://arxiv.org/abs/2606.10557

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