The kinematic and chemical properties of a potential core-forming clump: Perseus B1-E

We present ${}^{13}CO$ and $C^{18}O$ (1-0), (2-1), and (3-2) maps toward the core-forming Perseus B1-E clump using observations from the James Clerk Maxwell Telescope, the Submillimeter Telescope of the Arizona Radio Observatory, and the IRAM 30 m telescope. We find that the ${}^{13}CO$ and $C^{18}O$ line emission both have very complex velocity structures, indicative of multiple velocity components within the ambient gas. The (1–0) transitions reveal a radial velocity gradient across B1-E of $\sim 1km{s}^{-1}p{c}^{-1}$ that increases from northwest to southeast, whereas the majority of the Perseus cloud has a radial velocity gradient increasing from southwest to northeast. In contrast, we see no evidence of a velocity gradient associated with the denser Herschel-identified substructures in B1-E. Additionally, the denser substructures have much lower systemic motions than the ambient clump material, which indicates that they are likely decoupled from the large-scale gas. Nevertheless, these substructures themselves have broad line widths (∼0.4 $km{s}^{-1}$) similar to that of the $C^{18}O$ gas in the clump, which suggests they inherited their kinematic properties from the larger-scale, moderately dense gas. Finally, we find evidence of $C^{18}O$ depletion only toward one substructure, B1-E2, which is also the only object with narrow (transonic) line widths. We suggest that as prestellar cores form, their chemical and kinematic properties are linked in evolution, such that these objects must first dissipate their turbulence before they deplete in CO.