TY - JOUR

T1 - Linear kinetic theory of instabilities of a gravitating stellar disk

AU - Griv, Evgeny

AU - Gedalin, Michael

AU - Eichler, David

AU - Yuan, Chi

N1 - Funding Information:
This work was performed in part under the auspices of the Israeli Ministry of Science, the Israeli Ministry of Immigrant Absorption, the Israel – U.S. Binational Science Foundation, the Israel Science Foundation founded by the Academy of Sciences and Humanities, and the Academia Sinica in Taiwan. The authors thank Profs. Tzi-Hong Chiueh, Alexei M. Fridman, Peter Goldreich, Muzafar N. Mak-sumov, William Peter, Shlomi Pistinner, and Frank H. Shu for their interest in the work and for valuable suggestions. In part, this work was done while one of the authors (E. G.) was a Senior Postdoctoral Fellow at the ASIAA during 1996–1997. E. G. would like to thank Yi-Nan Chin, Minho Choi, Yi-Jehng Kuan, Jeremy Lim, Kwok-Yung Lo, and Jun-Hui Zhao for many useful discussions during his two-year stay, and all the staff of ASIAA for their hospitality.

PY - 2000/1/1

Y1 - 2000/1/1

N2 - Linear kinetic theory is developed to describe collective oscillations (and their instabilities) propagating in a rapidly rotating disk of stars, representing a highly flattened galaxy. The analysis is carried out for the special case of a self-gravitating, infinitesimally thin, and spatially inhomogeneous system, taking into account the effects both of thermal movements of stars and of gravitational encounters between stars and giant molecular clouds of an interstellar medium. The star-cloud encounters are described with the use of the Landau collision integral. The dynamics of gravity perturbations with rare interparticle encounters is considered. Such a disk is treated by employing the well elaborated mathematical formalisms from plasma perturbation theory using normal-mode analysis. In particular, the method of solving the Boltzmann equation is applied by integration along paths, neglecting the influence of star-cloud encounters on the distribution of stars in the zeroth-order approximation. We are especially interested in important kinetic effects due to wave-star resonances, which we have little knowledge about. The kinetic effects are introduced via a minor drift motion of stars which is computed from the equations of stellar motion in an unperturbed central force field of a galaxy. The dispersion laws for two main branches of disk's oscillations, that is the classical Jeans branch and an additional gradient branch, are deduced. The resonant Landau-type instabilities of hydrodynamically stable Jeans and gradient gravity perturbations is considered to be a long-term generating mechanism for propagating density waves, thereby leading to spiral-like and/or ring-like patterns in the flat galaxies.

AB - Linear kinetic theory is developed to describe collective oscillations (and their instabilities) propagating in a rapidly rotating disk of stars, representing a highly flattened galaxy. The analysis is carried out for the special case of a self-gravitating, infinitesimally thin, and spatially inhomogeneous system, taking into account the effects both of thermal movements of stars and of gravitational encounters between stars and giant molecular clouds of an interstellar medium. The star-cloud encounters are described with the use of the Landau collision integral. The dynamics of gravity perturbations with rare interparticle encounters is considered. Such a disk is treated by employing the well elaborated mathematical formalisms from plasma perturbation theory using normal-mode analysis. In particular, the method of solving the Boltzmann equation is applied by integration along paths, neglecting the influence of star-cloud encounters on the distribution of stars in the zeroth-order approximation. We are especially interested in important kinetic effects due to wave-star resonances, which we have little knowledge about. The kinetic effects are introduced via a minor drift motion of stars which is computed from the equations of stellar motion in an unperturbed central force field of a galaxy. The dispersion laws for two main branches of disk's oscillations, that is the classical Jeans branch and an additional gradient branch, are deduced. The resonant Landau-type instabilities of hydrodynamically stable Jeans and gradient gravity perturbations is considered to be a long-term generating mechanism for propagating density waves, thereby leading to spiral-like and/or ring-like patterns in the flat galaxies.

UR - http://www.scopus.com/inward/record.url?scp=0034366411&partnerID=8YFLogxK

U2 - 10.1023/A:1002091325620

DO - 10.1023/A:1002091325620

M3 - Article

AN - SCOPUS:0034366411

SN - 0004-640X

VL - 271

SP - 21

EP - 58

JO - Astrophysics and Space Science

JF - Astrophysics and Space Science

IS - 1

ER -