First clear detection of the CCS Zeeman splitting toward the pre-stellar core, Taurus Molecular Cloud-1

Abstract

We report a first clear detection of the Zeeman splitting of a CCS emission line at 45 GHz toward a nearby prestellar dense filament, Taurus Molecular Cloud-1. We observed HC${}_3$N non-Zeeman line simultaneously as the CCS line, and did not detect any significant splitting of HC${}_3$N line. Thus, we conclude that our detection of the CCS Zeeman splitting is robust. The derived \textcolor{black}{line-of-sight} magnetic field strength is about 117 $\pm$ 21 $\mu$G, which corresponds to the normalized mass-to-magnetic flux ratio of 2.2 if we adopt the inclination angle of 45${}^{\circ }$. Thus, we conclude that the TMC-1 filament is magnetically supercritical. Recent radiative transfer calculations of CCS and HC${}_3$N lines along the line of sight suggest that the filament is collapsing with a speed of $\sim$ 0.6 km s${}^{-1}$, which is comparable to three times the isothermal sound speed. This infall velocity appears to be consistent with the evolution of a gravitationally-infalling core.

23 pages, 8 figures, PASJ in press