Collapse and fragmentation of rotating magnetized clouds – I. Magnetic flux–spin relation |
| |
| Authors: | Masahiro N Machida Tomoaki Matsumoto Kohji Tomisaka Tomoyuki Hanawa |
| |
| Institution: | Centre for Frontier Science, Chiba University, Yayoicho 1-33, Inageku, Chiba 263-8522, Japan;Department of Physics, Kyoto University, Kyoto 606-8502, Japan;Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan;National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan |
| |
| Abstract: | We discuss the evolution of the magnetic flux density and angular velocity in a molecular cloud core, on the basis of three-dimensional numerical simulations, in which a rotating magnetized cloud fragments and collapses to form a very dense optically thick core of >5 × 1010 cm?3 . As the density increases towards the formation of the optically thick core, the magnetic flux density and angular velocity converge towards a single relationship between the two quantities. If the core is magnetically dominated its magnetic flux density approaches 1.5( n /5 × 1010 cm?3)1/2 mG , while if the core is rotationally dominated the angular velocity approaches 2.57 × 10?3 ( n /5 × 1010 cm?3)1/2 yr?1 , where n is the density of the gas. We also find that the ratio of the angular velocity to the magnetic flux density remains nearly constant until the density exceeds 5 × 1010 cm?3 . Fragmentation of the very dense core and emergence of outflows from fragments will be shown in the subsequent paper. |
| |
| Keywords: | MHD stars: formation ISM: clouds ISM: magnetic fields |
|
|
