تقرير
CO(2-1)/CO(1-0) line ratio on $\sim$100 parsec scale in the nearby barred galaxy NGC1300
| العنوان: | CO(2-1)/CO(1-0) line ratio on $\sim$100 parsec scale in the nearby barred galaxy NGC1300 |
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| المؤلفون: | Maeda, Fumiya, Egusa, Fumi, Ohta, Kouji, Fujimoto, Yusuke, Habe, Asao, Asada, Yoshihisa |
| سنة النشر: | 2021 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies |
| الوصف: | CO(2-1) emission is often used as a tracer of the giant molecular clouds (GMCs) as an alternative to CO(1-0) emission in recent years. Therefore, understanding the environmental dependence of the line ratio of CO(2-1)/CO(1-0), $R_{21}$, on GMC scale is important to accurately estimate the mass of the GMCs. We thus measured the $R_{21}$ in the strongly barred galaxy NGC1300, where star formation activity strongly depends on galactic structure, on $\sim 100$ pc scale. CO images were obtained from ALMA and Nobeyama 45-m telescope. The resultant typical $R_{21}$ in NGC1300 is $0.57 \pm 0.06$. We find environmental variations in $R_{21}$; it is the highest in the bar-end region ($0.72 \pm 0.08$), followed by arm ($0.60 \pm 0.07$) and bar regions ($0.50 \pm 0.06$). GMCs with H$\alpha$ emission show a systematically higher ratio ($0.67 \pm 0.07$) than those without H$\alpha$ ($0.47 \pm 0.05$). In the bar region, where massive star formation is suppressed, H$\alpha$ emission is not associated with most GMCs, resulting in the lowest $R_{21}$. These results raise a possibility that properties of GMCs derived from CO(2-1) observations with the assumption of a constant $R_{21}$ are different from those derived from CO(1-0) observations. Furthermore, we find the $R_{21}$ measured on kpc scale tends to be lower than that of the GMCs probably due to the presence of an extended diffuse molecular gas in NGC1300. Comment: 18 pages, 14 figures, accepted for publication in ApJ |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.3847/1538-4357/ac4505 |
| URL الوصول: | http://arxiv.org/abs/2112.11470 |
| رقم الأكسشن: | edsarx.2112.11470 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.3847/1538-4357/ac4505 |
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