Effects of magnetic field and far-ultraviolet radiation on the structures of bright-rimmed clouds.
MOTOYAMA K., UMEMOTO T., SHANG H. and HASEGAWA T.
Abstract (from CDS):
The bright-rimmed cloud SFO 22 was observed with the 45 m telescope of Nobeyama Radio Observatory in the 12CO (J = 1-0), 13CO (J = 1-0), and C18O (J = 1-0) lines, where well-developed head-tail structure and small line widths were found. Such features were predicted by radiation-driven implosion models, suggesting that SFO 22 may be in a quasi-stationary equilibrium state. We compare the observed properties with those from numerical models of a photoevaporating cloud, which include effects of magnetic pressure and heating due to strong far-ultraviolet (FUV) radiation from an exciting star. The magnetic pressure may play a more important role in the density structures of bright-rimmed clouds than the thermal pressure that is enhanced by the FUV radiation. The FUV radiation can heat the cloud surface to near 30 K; however, its effect is not enough to reproduce the observed density structure of SFO 22. An initial magnetic field of 5 µG in our numerical models produces the best agreement with the observations, and its direction can affect the structures of bright-rimmed clouds.