IS THE TAURUS B213 REGION A TRUE FILAMENT?: OBSERVATIONS OF MULTIPLE CYANOACETYLENE TRANSITIONS

We have obtained spectra of the J = 2-1 and 10-9 transitions of cyanoacetylene (HC3N) toward a collection of positions in the most prominent filament, B213, in the Taurus molecular cloud. The analysis of the excitation conditions of these transitions reveals an average gas H-2 volume density of (1.8 +/- 0.7) x10(4) cm(-3). Based on column density derived from the Two Micron All Sky Survey and this volume density, the line-of-sight dimension of the high-density portion of B213 is found to be similar or equal to 0.12 pc, which is comparable to the smaller projected dimension and much smaller than the elongated dimension of B213 (similar to 2.4 pc). B213 is thus likely a true cylinder-like filament rather than a sheet seen edge-on. The line width and velocity gradient seen in HC3N are also consistent with Taurus B213 being a self-gravitating filament in the early stage of either fragmentation and/or collapse.