12CO and 13CO observation of the low-metallicity dwarf galaxy DDO 154

IF 2.2 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Publications of the Astronomical Society of Japan Pub Date : 2023-11-17 DOI:10.1093/pasj/psad074
Shinya Komugi, Miku Inaba, Tetsuo Shindou
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Abstract

The conversion factor from carbon monoxide (CO) intensity to molecular gas mass is a source of large uncertainty in understanding gas and its relation to star formation in galaxies. In particular, the conversion factor in low-metallicity environments have remained elusive, as currently only two galaxies have been detected in any CO isotopes in environments with 12 + log (O$/$H) < 8.0. Here we report 12CO (J = 1–0) and 13CO (J = 1–0) observations towards a star-forming region in DDO 154, a low-metallicity dwarf irregular galaxy at 12 + log (O$/$H) = 7.67. This is a re-observation of a previous non-detection at higher angular and velocity resolution. No significant emission was detected. By estimating the molecular gas mass from associated star formation, we find that DDO 154 has a conversion factor of more than 103 times the Milky Way. Alternatively, if we estimate molecular mass using dust continuum emission, the conversion factor is at least 2 orders of magnitude larger than the Milky Way. These estimates signify a large amount of CO-dark molecular gas in this galaxy.
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低金属丰度矮星系DDO 154的12CO和13CO观测
从一氧化碳(CO)强度到分子气体质量的转换因子是理解气体及其与星系中恒星形成关系的一个很大的不确定性来源。特别是,低金属丰度环境中的转换因子仍然难以捉摸,因为目前只有两个星系在12 + log (O$/$H)的环境中检测到任何CO同位素。8.0. 在这里,我们报告了12CO (J = 1-0)和13CO (J = 1-0)对DDO 154恒星形成区域的观测,DDO 154是一个低金属量的矮不规则星系,12 + log (O$/$H) = 7.67。这是在更高的角度和速度分辨率下对先前未检测的重新观测。没有检测到明显的排放物。通过估算伴星形成的分子气体质量,我们发现DDO 154的换算系数超过了银河系的103倍。或者,如果我们用尘埃连续辐射来估计分子质量,转换因子至少比银河系大2个数量级。这些估计表明在这个星系中有大量的co -暗分子气体。
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来源期刊
Publications of the Astronomical Society of Japan
Publications of the Astronomical Society of Japan 地学天文-天文与天体物理
CiteScore
4.10
自引率
13.00%
发文量
98
审稿时长
4-8 weeks
期刊介绍: Publications of the Astronomical Society of Japan (PASJ) publishes the results of original research in all aspects of astronomy, astrophysics, and fields closely related to them.
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