The Cool Dark Globule CB68 and Its Associated Protostar: Geometry, Kinematics, Magnetic Vectors, and Pressure Balance

Abstract

CB68 is a nearby cool dark globule. We observed CB68 near a radial velocity around +5.5 km s-1 in the 12CO, 13CO, and C 18O gas in J = 3-2 covering a 2' × 2' area, and we reanalyzed previous observations of the thermal dust continuum and linear polarization near the same wavelength (850 μm), same angular resolution (14''), and same antenna. We find that the gaseous core has a disklike intensity elongation near a P.A. of 45° with a velocity gradient along that P.A.: a northeast blueshift and a southwest redshift, suggestive of a rotating gas; this gas P.A. is similar to the elongation of the dust emission near a P.A. of 45°. We map the low-velocity blue southeast outflow and red northwest outflow; the CO gas outflow contours are elongated at a P.A. near -45°, similar to the elongation of the polarization percentage contours near -45°. We estimate the Chandrasekhar-Fermi strength of the hourglass-shaped magnetic field to be 120-130 μG in the sky plane. This strength is nearly a factor of 10-20 greater than the Zeeman line-of-sight data (7-10 μG) in the nearby tenuous cloud, outside CB68 proper. We deduce the energy and pressure components in the cool globule and in the hot surrounding region. We find an imbalance in pressure, which we tentatively assign to a neglected halo component (a reservoir of tenuous halo gas still infalling toward the disklike object CB68).