Speaker
Description
Filamentary molecular clouds are now recognized as the fundamental structures that set the initial conditions of star formation. However, their formation mechanism remains an open question. Among the proposed scenarios, converging gas flows induced by colliding gas layers have emerged as a compelling candidate (Inoue et al. 2018; Arzoumanian et al. 2018, 2022), yet direct observational constraints on how filament properties—such as column density and line mass—are established are still under debate. Here, we present new observational evidences linking filament formation to colliding gas flows in the Perseus molecular cloud, one of the nearest star-cluster-forming regions at a distance of ~300 pc. Using the Nobeyama 45-m telescope, we performed wide-field observations of $^{12}$CO, $^{13}$CO, and C$^{18}$O toward two subregions of Perseus (NGC 1333: 1 deg. $\times$ 1 deg., IC 348: 45 arcmin $\times$ 20 arcmin), tracing gas over a wide range of densities (10$^2$--10$^5$). We identify two molecular cloud components with a velocity separation of ~5 km s$^{-1}$ in both NGC 1333 and IC 348, as observed in $^{12}$CO and $^{13}$CO. These components are connected in velocity space and exhibit complementary spatial distributions—hallmarks of cloud–cloud collisions (Fukui et al. 2021). The two velocity components are also confirmed in HI data obtained with the Arecibo telescope, suggesting that cloud–cloud collisions over a wide dynamic range are occurring throughout Perseus. In C$^{18}$O, we detect a rich network of filaments (20 in IC 348 and 54 in NGC 1333) with a characteristic width of ~0.1 pc. Strikingly, all filaments with line masses exceeding 100 $M_\odot$ pc$^{-1}$ are confined to regions where the two velocity components overlap. We also find that $^{12}$CO filamentary structure in areas lacking C$^{18}$O detection, and these $^{12}$CO filaments are accompanied by the two HI gas components with column density of $\sim$5$\times$10$^{20}$ cm $^{-2}$ for each. Based on these results, we suggest that a collision between $^{13}$CO-detectable gas forms a multiple network of filaments with large line mass, and a collision between HI gas formed the $^{12}$CO filaments. Hence, the line mass of filaments is likely regulated by the pre-collision gas density. We will further discuss the origin and driving mechanisms of cloud–cloud collisions across the Perseus molecular cloud.
| Participate the oral/poster presentation award competition | No |
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