Work

Differential Rotation and Turbulence in Extended H i Disks

Year: 1999

Type: article

Abstract: When present, extended disks of neutral hydrogen around spiral galaxies show a remarkably uniform velocity dispersion of ~6 km s -1 . Since stellar winds and supernovae are largely absent in such regions, neither the magnitude nor the constancy of this number can be accounted for in the classical picture in which interstellar turbulence is driven by stellar energy sources. Here we suggest that magnetic fields with strengths of a few microgauss in these extended disks allow energy to be extracted from galactic differential rotation through MHD-driven turbulence. The magnitude and constancy of the observed velocity dispersion may be understood if its value is Alfvénic. Moreover, by providing a simple explanation for a lower bound to the gaseous velocity fluctuations, MHD processes may account for the sharp outer edge to star formation in galaxy disks.

Source: The Astrophysical Journal

DOI: 10.1086/306728

Authors: J. A. Sellwood, Steven A. Balbus

Institutions: Rutgers, The State University of New Jersey, Isaac Newton Institute for Mathematical Sciences, University of Cambridge, University of Virginia

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: bronze

Funders: National Science Foundation, National Aeronautics and Space Administration, Division of Mathematical Sciences

Awards: Galaxy Dynamics and Dark Matter, Magnetohydrodynamical Problems in the Galaxy