Loading...

Density waves in debris discs and galactic nuclei

Jalali, M. A ; Sharif University of Technology | 2012

347 Viewed
  1. Type of Document: Article
  2. DOI: 10.1111/j.1365-2966.2012.20469.x
  3. Publisher: 2012
  4. Abstract:
  5. We study the linear perturbations of collisionless near-Keplerian discs. Such systems are models for debris discs around stars and the stellar discs surrounding supermassive black holes at the centres of galaxies. Using a finite-element method, we solve the linearized collisionless Boltzmann equation and Poisson's equation for a wide range of disc masses and rms orbital eccentricities to obtain the eigenfrequencies and shapes of normal modes. We find that these discs can support large-scale 'slow' modes, in which the frequency is proportional to the disc mass. Slow modes are present for arbitrarily small disc mass so long as the self-gravity of the disc is the dominant source of apsidal precession. We find that slow modes are of two general types: parent modes and hybrid child modes, the latter arising from resonant interactions between parent modes and singular van Kampen modes. The most prominent slow modes have azimuthal wavenumbers m= 1 and m= 2. We illustrate how slow modes in debris discs are excited during a fly-by of a neighbouring star. Many of the non-axisymmetric features seen in debris discs (clumps, eccentricity, spiral waves) that are commonly attributed to planets could instead arise from slow modes; the two hypotheses can be distinguished by long-term measurements of the pattern speed of the features
  6. Keywords:
  7. Galaxies: kinematics and dynamics ; Galaxies: nuclei ; Methods: numerical ; Planets and satellites: formation ; Protoplanetary discs
  8. Source: Monthly Notices of the Royal Astronomical Society ; Volume 421, Issue 3 , 2012 , Pages 2368-2383 ; 00358711 (ISSN)
  9. URL: http://mnras.oxfordjournals.org/content/421/3/2368