CO(J = 1–0) Observations of a Filamentary Molecular Cloud in the Galactic Region Centered at l = 150°, b = 3.°5

Abstract

We present large-field (4.25 × 3.75 deg 2 ) mapping observations toward the Galactic region centered at l = 150 • , b = 3.5 • in the J = 1 − 0 emission line of CO isotopologues ( 12 CO, 13 CO, and C 18 O), using the 13.7 m millimeter-wavelength telescope of the Purple Mountain Observatory. Based on the 13 CO observations, we reveal a filamentary cloud in the Local Arm at a velocity range of −0.5 to 6.5 km s −1 . This molecular cloud contains 1 main filament and 11 sub-filaments, showing the so-called "ridge-nest" structure. The main filament and three sub-filaments are also detected in the C 18 O line. The velocity structures of most identified filaments display continuous distribution with slight velocity gradients. The measured median excitation temperature, line width, length, width, and linear mass of the filaments are ∼9.28 K, 0.85 km s −1 , 7.30 pc, 0.79 pc, and 17.92 M ⊙ pc −1 , respectively, assuming a distance of 400 pc. We find that the four filaments detected in the C 18 O line are thermally supercritical, and two of them are in the virialized state, and thus tend to be gravitationally bound. We identify in total 146 13 CO clumps in the cloud, about 77% of the clumps are distributed along the filaments. About 56% of the virialized clumps are found to be associated with the supercritical filaments. Three young stellar object (YSO) candidates are also identified in the supercritical filaments, based on the complementary infrared (IR) data. These results indicate that the supercritical filaments, especially the virialized filaments, may contain star-forming activities.

CO (J = 1–0) Observations toward Filamentary Molecular Clouds in the Galactic Region with l = [169.°75, 174.°75], b = [−0.°75, 0.°5]

“…The results are listed in Table 2. The mean width from these eight filaments is 1.13±0.01 pc, which is much larger than 0.1 pc but similar to our previous work (0.79 pc; Xiong et al 2017). We note that the resolution of our observations (50″, corresponding to ∼0.4 pc at a distance of ∼1.7 kpc) may not be sufficient to resolve the inner width of the filaments.…”

“…Our work is part of the Milky Way Imaging Scroll Painting (MWISP) project, 7 conducted by the Purple Mountain Observatory (PMO) using the PMO 13.7 m radio telescope to investigate the molecular gas along the northern Galactic plane with the 12 CO, 13 CO, and C 18 O(J = 1 − 0) lines. Our work in the G150 region (see Xiong et al 2017) showed that the molecular gas in this region consists of one main filament in the inner area with a higher column density and 11 subfilaments in the outer area with lower column densities, forming the so-called "ridge-nest" structure. About 75% of the CO dense clumps are associated with the filaments, and 56% of the virialized clumps are associated with the gravitationally bound filaments.…”

“…We further calculate the radial density profiles of filaments based on the H 2 column density (shown in panel (d2) of Figures 6,8,10,12,and 14). Using the same method as Palmeirim et al (2013) and Xiong et al (2017), we first determine the tangential direction of each pixel along the position of each filament, shown as the solid white line in each (d2) panel. For each pixel, we then derive one column density profile perpendicular to the tangential direction.…”

“…Therefore, the gravitational stability of a filament is determined by this critical mass. If the line mass of the filament is greater than the critical value, the filament is gravitationally unstable and will fragment into clumps along its length that may lead to star formation (e.g., Goldsmith et al 2008;Bontemps et al 2010;Xiong et al 2017). On the contrary, with the line mass lower than the critical value, the filament is gravitationally unbound or in an expanding state and is even expected to disperse during the turbulent crossing time (Arzoumanian et al 2013), unless confined by the external pressure (Fischera & Martin 2012).…”

TRAO Survey of Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO FUNS). I. Dynamics and Chemistry of L1478 in the California Molecular Cloud

“…Turbulence motions in filaments and dense cores are important to the formation of filaments and dense cores. Numerical simulations of supersonic turbulence gave a result generating dense stuructures like sheets, filaments, and cores (e.g., Padoan et al 2001a;Xiong et al 2017;Haugbølle et al 2018). Padoan et al (2001a) proposed that filaments can form by collision of turbulent flows, and dissipation of turbulence makes the dense cores.…”