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J. Shen, J. A. Sellwood (Rutgers University)
More than two thirds of disk galaxies are strongly or weakly barred. Many barred galaxies today harbor massive concentrations of gas in their centers, and some are known to possess supermassive black holes (SBHs) and their associated stellar cusps. Previous theoretical work has suggested that a bar in a galaxy could be dissolved by the formation of a mass concentration in the center, although the precise mass and degree of central concentration required is not well-established. We report an extensive study of the effects of central masses on bars in high-quality N-body simulations of galaxies. We have varied the growth rate of the central mass, its final mass and degree of concentration to examine how these factors affect the evolution of the bar. Our main conclusions are: (1) bars are more robust than previously thought. The central mass has to be as large as several percent of the disk mass to completely destroy the bar on a short a time scale. (2) for a given mass, dense objects cause the greatest reduction in bar amplitude, while significantly more diffuse objects have a lesser effect; (3) the bar amplitude always decreases as the central mass is grown, and continues to decay thereafter on a cosmological time-scale. Thus the current masses of SBHs are probably too small, even when dressed with a stellar cusp, to affect the bar in their host galaxies. The molecular gas concentrations found in some barred galaxies are also too diffuse to affect the amplitude of the bar significantly. These findings naturally explain the apparent high percentage of barred galaxies in the presence of central massive concentrations, and have important implications for the formation and survival of bars in such galaxies.
The author(s) of this abstract have provided an email address for comments about the abstract: shen@physics.rutgers.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.