Effects of Magnetic Field and FUV Radiation on the Structures of Bright-rimmed Clouds

TL;DR

This study investigates how magnetic fields and FUV radiation influence the structure of bright-rimmed clouds, using observations and numerical models to determine the dominant factors shaping these clouds.

Contribution

It introduces numerical models that incorporate magnetic pressure and FUV heating to better understand bright-rimmed cloud structures, highlighting magnetic fields as a key factor.

Findings

Magnetic pressure significantly influences cloud density structures.

FUV radiation heats cloud surfaces but does not dominate structural shaping.

Magnetic field strength of 5 μG aligns best with observations.

Abstract

The bright-rimmed cloud SFO 22 was observed with the 45 m telescope of Nobeyama Radio Observatory in the ^{12}CO (J = 1-0), ^{13}CO (J = 1-0), and C^{18}O (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 photo-evaporating 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 \mu G in our numerical models produces the best agreement with the observations, and its direction can affect the structures of bright-rimmed clouds.