Publication: Spiral and Bar Instabilities Provoked by Dark Matter Satellites

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Title Spiral and Bar Instabilities Provoked by Dark Matter Satellites
Authors/Editors* J. Dubinski, J.-R. Gauthier, L.M. Widrow, S. Nickerson
Where published* In proceedings The Formation and Evolution of Disk Galaxies, eds. E. Corsini and J. Funes
How published* Proceedings
Year* 2008
Pages 4
Keywords Galactic Dynamics; Spiral Galaxies; Dark Matter
We explore the secular dynamical evolution of an N-body model of M31 in the presence of a population of 100 dark matter satellites over 10 Gyr. The satellite population has structural and kinematic characteristics modelled to follow the predictions of Lambda-CDM cosmological simulations. Vertical disk heating is a small effect despite many interactions with the satellite population with only a 20% increase in vertical velocity dispersion sigma_z and the disk scale height z_d at the equivalent solar radius R = 2.5R_d . However, the stellar disk is noticeably flared after 10 Gyr with z_d nearly doubling at the disk edge. Azimuthal disk heating is much larger with sigma_R and sigma_z both increasing by 1.7x. However, in a control experiment without satellites dispersion increases by 1.5x suggesting that most of the effect is due to heating through scattering off of spiral structure excited by swing-amplified noise. Surprisingly, direct impacts of satellites on the disk can excite spiral structure with a significant amplitude and in some cases impacts close to the disk center also induce the bar instability. The large number of dark matter satellite impacts expected over a galaxy's lifetime may be a significant source of external perturbations for driving disk secular evolution.
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