Astrophys. J., 627, 263-276 (2005/July-1)
A cool magnetized shell wrapped around the hot H II region S106: geometry, kinematics, magnetic vectors, and pressure balance.
VALLEE J.P. and FIEGE J.D.
Abstract (from CDS):
In the optical, the exciting star S106 IR resides in a conspicuous dust lane and it ionizes two bright, sharp gas lobes on both sides of the dust lane. Wrapped around this hot (10,000 K) ionized (H II) optical bipolar nebula (the two gas lobes), we see a cool shell in the millimeter-submillimeter radio. Outside the cool shell, there is an even colder (<22 K), large (20'=4 pc), lower density molecular cloud. In this paper, we study the cool gas (spectroscopy in three lines), the cool dust (continuum imaging), and the magnetic field (polarimetry) in the shell, all made near a wavelength of 850 µm with the same angular resolution of 14" using the James Clerk Maxwell Telescope (JCMT). Near a radial velocity of -1 km/s, we used 12CO, 13CO, and C18O in the J=3-2 lines to map the cool (32 K) gas in the shell peaks on both sides of the hot cavity walls, extending 2' (0.4 pc) in north-south length with a 100" (0.3 pc) east-west diameter. Also, we used dust continuum emission and its linear polarization to map the cool shell. For the vertical cool shell, sandwiched between a hot region and a colder cloud, we find that the shell's combined pressure (made up mostly of turbulence and total magnetic field) can withstand the turbulent and thermal pressure of the hot ionized outflow, although the cool gas shell is slowly being eroded by the ionization process going on. The large-scale magnetic field appears roughly vertical along the roughly vertical gas shell. The magnetic field in the vertical shell (away from the central dust lane) has an estimated value near 400 µG. In the horizontal dust lane, the magnetic field appears roughly horizontal and parallel to the dust lane encompassing the IR and FIR components. Here the magnetic field derived from various methods has an estimated plane-of-sky median value near 570 µG, while the previously published Zeeman data indicated a line-of-sight strength near +240 µG.
ISM: Dust, Extinction - ISM: H II Regions - Infrared: ISM - ISM: Magnetic Fields - Polarization - Stars: Formation
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