A wide-field CO survey towards the California Molecular Filament

Abstract

We present the survey of ${}^{12}$CO/${}^{13}$CO/C${}^{18}$O (J=1-0) toward the California Molecular Cloud (CMC) within the region of 161.75${}^{\circ }⩽l⩽$ 167.75${}^{\circ }$,-9.5${}^{\circ }⩽b⩽$-7.5${}^{\circ }$, 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 ${}^{12}$CO, ${}^{13}$CO, and C${}^{18}$O is about 2.59$\times$10${}^4$ M${}_{\odot }$, 0.85$\times$10${}^4$ M${}_{\odot }$, and 0.09$\times$10${}^4$ M${}_{\odot }$, respectively. A large-scale continuous filament extending about 72 pc is revealed from the ${}^{13}$CO images. A systematic velocity gradient perpendicular to the major axis appears and is measured to be $\sim$ 0.82 km s${}^{-1}$ pc${}^{-1}$. The kinematics along the filament shows an oscillation pattern with a fragmentation wavelength of $\sim$ 2.3 pc and velocity amplitude of $\sim$ 0.92 km s${}^{-1}$, which may be related with core-forming flows. Furthermore, assuming an inclination angle to the plane of the sky of 45${}^{\circ }$, the estimated average accretion rate is $\sim$ 101 M${}_{\odot }$ Myr${}^{-1}$ for the cluster LkH$\hat{I}\pm$ 101 and $\sim$ 21 M${}_{\odot }$ Myr${}^{-1}$ for the other regions. In the C${}^{18}$O 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 C${}^{18}$O cores are extracted, of which 181 are starless cores. Roughly 37$\%$ (67/181) of the starless cores have $\hat{I}{\pm }_{\text{vir}}$ 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.

28 pages, 15 figures, accepted by ApJ