Abstract
Abstract We present the survey of 12CO/13CO/C18O (J = 1 − 0) toward the California molecular cloud (CMC) within the region of 161.°75 ≤ l ≤ 167.°75, −9.°5 ≤ b ≤ −7.°5 using the Purple Mountain Observatory (PMO) 13.7 m millimeter telescope. Adopting a distance of 470 pc, the mass of the observed molecular cloud estimated from 12CO, 13CO, and C18O is about 2.59 × 104, 0.85 × 104, and 0.09 × 104 M ⊙, respectively. A large-scale continuous filament extending about 72 pc is revealed from the 13CO images. A systematic velocity gradient perpendicular to the major axis appears and is measured to be ∼0.82 km s−1 pc−1. The kinematics along the filament shows an oscillation pattern with a fragmentation wavelength of ∼2.3 pc and velocity amplitude of ∼0.92 km s−1, which may be related to core-forming flows. Furthermore, assuming an inclination angle to the plane of the sky of 45°, the estimated average accretion rate is ∼101 M ⊙ Myr−1 for the cluster LkHα 101 and ∼21 M ⊙ Myr−1 for the other regions. In the C18O observations, the large-scale filament could be resolved into multiple substructures, and their dynamics are consistent with the scenario of filament formation from converging flows. Approximately 225 C18O cores are extracted, of which 181 are starless cores. Roughly 37% (67/181) of the starless cores have α vir less than 1. Twenty outflow candidates are identified along the filament. Our results indicate active early-phase star formation along the large-scale filament in the CMC region.
Highlights
Filamentary structures are ubiquitous in the interstellar medium (ISM)
We present the survey of 12CO/13CO/C18O (J=1-0) toward the California Molecular Cloud (CMC) within the region of 161.75◦ l 167.75◦, -9.5◦ b -7.5◦, using the Purple Mountain Observatory (PMO) 13.7 m millimeter telescope
Bright C18O emission outlines the ridgeline of the filamentary structure in the CMC region
Summary
Filamentary structures are ubiquitous in the interstellar medium (ISM). In the last decade, based on multi-wavelength observations (e.g., surveys with the Herschel Space Observatory), great progresses have been made in the relationship between filamentary molecular clouds and star formation (Andre et al 2010; Molinari et al 2010). It is widely accepted that filamentary molecular clouds play an important role in the process of star formation Both observational and theoretical studies suggest that large-scale supersonic compressed gas forms reticular structures firstly in the ISM, and reticular structures fragment and form prestellar cores due to the force of self-gravity, the cores evolve into stars (Andre et al 2014). The Milky Way Imaging Scroll Painting (MWISP) project is a large CO (J=1–0) multi-line survey towards the northern Galactic Plane, using the PMO-13.7 m millimeter telescope This unbiased survey provides us a good opportunity to study large-scale filamentary molecular clouds, as well as star formation therein
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