Structure of Magnetized Molecular Filaments


Observations of thermal dust emissions with Herschel satellite have revealed that molecular clouds consist of many filaments (Menshchikov et al. 2010). That is, the molecular filaments are the building blocks of interstellar clouds. On the other hand, near IR interstellar polarization indicates the filaments are extending in the perpendicular direction to the interstellar magnetic field (Sugitani et al. 2011). f5a f5c
Equilibrium solutions of isothermal clouds, in which the gravity is balanced with the Lorentz force, thermal pressure and the external pressure, are obtained with a self-consistent field method. The above figures show typical solutions of cross-cut of these filaments. Dashed and closed solid curves represent, respectively, magnetic field lines and isodensity contour lines. Left and right panels show solutions with low and high center-to-surface density ratios, respectively.

We obtained an empirical relation between the maximum supported mass against the self-gravity, λmax, and magnetic flux, Φcl, as,
λmax≅0.24 Φcl/G1/2 + 1.66 cs2,
where λmax and Φcl represent, respectively, mass of the filament per unit length and one-half of the magnetic flux per unit length of the filament. For Φcl > 3 pc μG (cs/190m s-1)2, the magnetic force (the Lorentz force) plays more important role than the thermal pressure in determining the equilibria.

The importance of this article is that structure and the maximum mass of the building block of molecular clouds are first determined theoretically.
Magnetohydrostatic Equilibrium Structure and Mass of Filamentary Isothermal Cloud Threaded by Lateral Magnetic Field, by Tomisaka, Kohji, 2014, ApJ, 784, 1
[ADS] [arXiv]
Kohji Tomisaka (private website)