Pitch Angle of Galactic Spiral Arms

Abstract

One of the key parameters that characterize spiral arms in disk galaxies is a pitch angle that measures the inclination of a spiral arm to the direction of galactic rotation. The pitch angle differs from galaxy to galaxy, which suggests that the rotation law of galactic disks determines it. In order to investigate the relation between the pitch angle of spiral arms and the shear rate of galactic differential rotation, we perform local $N$-body simulations of pure stellar disks. We find that the pitch angle increases with the epicycle frequency and decreases with the shear rate and obtain the fitting formula. This dependence is explained by the swing amplification mechanism.

17 pages, 8 figures, accepted for publication in ApJ

References in corpus (3)

• Physical Properties of Tidal Features in Interacting Disk Galaxies
• The origin of large peculiar motions of star-forming regions and spiral structures of our Galaxy
• Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. I. Method outline

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• Dynamics of Porous Dust Aggregates and Gravitational Instability of Their Disk
• Coherent Stellar Motion in Galactic Spiral Arms by Swing Amplification