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arXiv · 2404.01427

Quantitative analysis of the molecular gas morphology in nearby disk galaxies

Takashi Yamamoto·Daisuke Iono·Toshiki Saito·Nario Kuno·Sophia K. Stuber·Daizhong Liu·Thomas G. Williams
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Abstract

We present a quantitative and statistical analysis of the molecular gas morphology in 73 nearby galaxies using high spatial resolution CO ($J$ = 2-1) data obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) by the PHANGS large program. We applied three model-independent parameters: Concentration ($C$), Asymmetry ($A$), and Clumpiness ($S$) which are commonly used to parameterize the optical and infrared morphology of galaxies. We find a clear apparent correlation between $A$ and $S$, with a Spearman's rank correlation coefficient of $0.52$ with a $p$-value of $2\times10^{-6}$. This suggests a higher abundance of molecular clumps (i.e. giant molecular cloud associations) in galaxies that display stronger distortion or biased large-scale molecular gas distribution. In addition, the analysis of the $C$ parameter suggests high central molecular concentration in most barred spiral galaxies investigated in this study. Furthermore, we found a positive correlation between the length of the bar structure ($R_\mathrm{bar}/R_{25}$) and the $C$ parameter, with a Spearman's rank correlation coefficient of $0.63$ with a $p$-value of $3.8 \times 10^{-5}$, suggesting that larger bar structure can facilitate overall molecular gas transport and yield higher central concentration than galaxies with shorter bars. Finally, we offer a possible classification scheme of nearby disk galaxies which is based on the CAS parameters of molecular gas.

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Takashi Yamamoto, Daisuke Iono, Toshiki Saito, Nario Kuno, Sophia K. Stuber, Daizhong Liu, Thomas G. Williams. 2024-04-01. Quantitative analysis of the molecular gas morphology in nearby disk galaxies. https://doi.org/10.1093/pasj%2Fpsae116

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