Pattern Speed of Lopsidedness in Galactic Disks

Chanda J. Jog

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arXiv · 0812.0670

Pattern Speed of Lopsidedness in Galactic Disks

Chanda J. Jog

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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.

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Chanda J. Jog. 2008-12-03. Pattern Speed of Lopsidedness in Galactic Disks. https://arxiv.org/abs/0812.0670

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