Pattern Speed of Lopsidedness in Galactic Disks
Abstract
The disks of spiral galaxies commonly show a lopsided mass distribution, with a typical fractional amplitude of 10 % for the Fourier component m=1. This is seen in both stars and gas, and the amplitude is higher by a factor of two for galaxies in a group. The study of lopsidedness is a new topic, in contrast to the extensively studied bars and two-armed spirals (m=2). Here, first a brief overview of the observations of disk lopsidedness is given, followed by a summary of the various mechanisms that have been proposed to explain its physical origin. These include tidal interactions, gas accretion, and a global instability. The pattern speed of lopsidedness in a real galaxy has not been measured so far, the various issues involved will be discussed. Theoretical studies have shown that the m=1 slow modes are long-lived, while the modes with a moderate pattern speed as triggered in interactions, last for only about a Gyr. Thus a measurement of the pattern speed of lopsided distribution will help identify the mechanism for its origin.
Cite
@article{arxiv.0812.0670,
title = {Pattern Speed of Lopsidedness in Galactic Disks},
author = {Chanda J. Jog},
journal= {arXiv preprint arXiv:0812.0670},
year = {2008}
}
Comments
7 pages, 7 figures, Invited review. To appear in "Tumbling, Twisting, and Winding Galaxies: Pattern Speeds along the Hubble Sequence", Padova, Italy, August 2008, E. M. Corsini and V. P. Debattista (eds.), to be published by Memorie della Societa` Astronomica Italiana