A Wide-field CO Survey toward the California Molecular Filament

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.

On the Spatial Distribution of 13CO Structures within 12CO Molecular Clouds

“…In another picture, MCs appear to be transient objects that may never reach a configuration of equilibrium (Passot et al 1995;Vazquez-Semadent et al 1995;Ballesteros-Paredes et al 1999;Vázquez-Semadeni et al 2003;Clark et al 2012;Ballesteros-Paredes et al 2020). They can form in the diffuse ISM through local compressions induced by the converging flows from the differential rotation and shear of the spiral arms (Kwan & Valdes 1983;Tomisaka 1984;Kwan & Valdes 1987), the passage of H II regions or supernova shells (Heiles 1979(Heiles , 1984Tenorio-Tagle & Bodenheimer 1988;Hartmann et al 2001), shock-wave passage (Bergin et al 2004;Clark et al 2012;Guo et al 2021), large-scale gravitational instability of rotating disk (Lin & Shu 1964;Roberts 1969;Shetty & Ostriker 2008;Tasker & Tan 2009;Dobbs et al 2011), cloud agglomeration (Oort 1954;Field & Saslaw 1965;Kwan & Valdes 1983;Tomisaka 1984;Dobbs & Baba 2014), and cloud-cloud collisions (Gilden 1984;Fukui et al 2014;Dobbs et al 2015;Fukui et al 2016;Gong et al 2017). In addition, the density fluctuations within MCs can be produced by a common hierarchy of interstellar converging flows, i.e., the supersonic dissipation in the ambient medium (Larson 1981;Myers 1983;Cernicharo et al 1985;Falgarone et al 1992;Heyer & Brunt 2004;…”

CO(J = 1 – 0) Observations toward the Filamentary Cloud in the Galactic Region of 153.°60 ≤ l ≤ 156.°50 and 1.°85 ≤ b ≤ 3.°50

“…The oscillation pattern along PV diagrams commonly appears in spectral line observations toward filamentary clouds (see, e.g., Jackson et al 2010;Hacar & Tafalla 2011;Hacar et al 2013;Guo et al 2021), which is generally interpreted as mass transport along the segment due to core accretion (Kirk et al 2013;Heitsch 2013;Henshaw et al 2014;Lu et al 2018). We estimate mass flow rates (  M) using the simple cylindrical model from Kirk et al (2013),…”

“…It is necessary to search for more filamentary clouds to reveal their gas dynamics in terms of filament fragmentation, core accretion, and highmass star formation. The Milky Way Imaging Scroll Painting (MWISP) project 3 is an unbiased, high-sensitivity CO multiline survey toward the northern Galactic plane (Su et al 2019;Sun et al 2021), which provides us with a good opportunity to study large-scale filamentary clouds (e.g., Guo et al 2021;Yuan et al 2021). In this work, we present observations of three CO isotope lines toward the Galactic region of 153°.6 l 156°.5 and 1°.85 b 3°.…”

“…For example, about 75% of pre-and protostellar cores were found to be located in filaments in the Herschel Gould Belt Survey (e.g., André et al 2014;Könyves et al 2015). Large-scale filaments containing dense molecular gas appear to form massive stars and clusters, e.g., Nessie (Jackson et al 2010;Mattern et al 2018), Orion (Bally 1981;Johnstone & Bally 1999;Tatematsu et al 2008), California (Lada et al 2009(Lada et al , 2017Guo et al 2021), and NGC 6334 (Russeil et al 2013;Fukui et al 2018), though the relevant mechanisms are still under study. Motte et al (2018) suggested an evolutionary picture for the formation of high-mass stars, which involves scenarios of a global hierarchical collapse and clump-fed accretion.…”

The Cassiopeia Filament: A Blown Spur of the Local Arm

“…Large-scale molecular filaments, with lengths of order 100 pc, play an important role in both star formation and Galactic structure. A number of large-scale molecular filaments were found in the past decade (see, e.g., Jackson et al 2010;Li et al 2013;Ragan et al 2014;Zucker et al 2015;Wang et al 2015Wang et al , 2016Abreu-Vicente et al 2016;Li et al 2016;Du et al 2017;Colombo et al 2021;Guo et al 2021). Depending on searching tracers and identifying methods, these filaments have various properties and can be generally divided into "giant molecular filaments" (GMFs; e.g., Ragan et al 2014;Abreu-Vicente et al 2016) and "bone-like" filaments (e.g., Wang et al 2015;Zucker et al 2015) two groups 7 (see properties summarized by Zucker et al 2018).…”