Velocity Structure and Molecular Formation in the Polaris Molecular Cloud

• DOI: 10.3847/1538-4357/adb418
• Publication Date: 2025-03-06T10:13:30Z
• Authors: Tomomi Shimoikura; Kazuhito Dobashi; Fumitaka Nakamura; Kotomi Taniguchi

Abstract We present a wide-field <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:mn>60</mml:mn> <mml:mi>′</mml:mi> <mml:mo>×</mml:mo> <mml:mn>30</mml:mn> stretchy="false">)</mml:mo> </mml:math> study of dense region within the Polaris Flare using 12 CO, 13 and C 18 O ( J = 1–0) observations at 15″ resolution, obtained with Nobeyama 45 m Radio Telescope. The analysis reveals molecular gas formation occurring column densities up to ∼10 21 cm −2 , evidenced by an anticorrelation between H i CO distributions, indicating active atomic-to-molecular conversion. found threshold density for ∼5 × 10 20 which is common among more evolved clouds. CO-to-H 2 conversion factor, X was be 0.7 (K km s −1 ) lower than solar neighborhood average. Our chemical models estimate cloud’s age ∼​​​​​​10 5 –10 6 yr, suggesting early stage cloud evolution. This interpretation consistent observed low factor. While virial suggests that entire gravitationally unbound, we identified several filamentary structures extending from main body. These filaments show systematic velocity gradients 0.5–1.5 pc velocities shows them falling toward body, following freefall model. ongoing mass accumulation processes through filaments, demonstrating gravitational can important even .