Spatial distribution of C4H and c-C3H2 in cold molecular cores

• Published in: arXiv.org 2024-06
• Main Authors: Liu, Yijia, Wang, Junzhi, Liu, Shu, Tang, Ningyu, Gong, Yan, Li, Yuqiang, LI, Juan, Luo, Rui, Xu, Yani
• Format: Article
• Language: English
• Subjects: Correlation coefficients; Equilibrium conditions; Interstellar chemistry; Interstellar matter; Local thermodynamic equilibrium; Organic chemistry; Spatial distribution
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2406.19740

C\(_4\)H and \(c\)-C\(_3\)H\(_2\), as unsaturated hydrocarbon molecules, are important for forming large organic molecules in the interstellar medium. We present mapping observations of C\(_4\)H (\(N\)=9\(-8\)) lines, \(c\)-C\(_3\)H\(_2\) (\(J_{Ka,Kb}\)=2\(_{1,2}\)-1\(_{0,1}\)) %at 85338.894 MHz and H\(^{13}\)CO\(^+\) (\(J\)=1\(-0\)) %at 86754.2884 MHz toward 19 nearby cold molecular cores in the Milky Way with the IRAM 30m telescope. C\(_4\)H 9--8 was detected in 13 sources, while \(c\)-C\(_3\)H\(_2\) was detected in 18 sources. The widely existing C\(_4\)H and \(c\)-C\(_3\)H\(_2\) molecules in cold cores provide material to form large organic molecules. Different spatial distributions between C\(_4\)H 9--8 and \(c\)-C\(_3\)H\(_2\) 2--1 were found. The relative abundances of these three molecules were obtained under the assumption of local thermodynamic equilibrium conditions with a fixed excitation temperature. The abundance ratio of C\(_4\)H to \(c\)-C\(_3\)H\(_2\) ranged from 0.34 \(\pm\) 0.09 in G032.93+02 to 4.65 \(\pm\) 0.50 in G008.67+22. A weak correlation between C\(_4\)H/H\(^{13}\)CO\(^+\) and \(c\)-C\(_3\)H\(_2\)/H\(^{13}\)CO\(^+\) abundance ratios was found, with a correlation coefficient of 0.46, which indicates that there is no tight astrochemical connection between C\(_4\)H and \(c\)-C\(_3\)H\(_2\) molecules.