Negative mass instability of flat galaxies

Journal Article · Sat Apr 01 04:00:00 EST 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156004· OSTI ID:6779989

Lovelace, R V.E.; Hohlfeld, R G

A study is made of the linear initial value problem of a flat, low-''temperature,'' self-gravitating disk for perturbations which are radially localized with vertical-bar..omega..: n..cap omega..vertical-bar/sup 2/, where ..omega.. is the angular frequency and n the azimuthal mode number (not =0) of the perturbation, and where ..cap omega.. (r) is the angular velocity of the differentially rotating disk matter at a radial distance r. We find that instability is possible in situations where the distribution function for angular momentum, f (r) equivalentsigmaapprox. =/sub kappa//sup -/2, has a maximum or minimum as a function of r and (dvertical-bardr) ..cap omega..not =0 at the extremum of f, where sigma (ir) is the surface mass-density of the disk, and kappa (r) is the epicyclic frequency. Approximate growth rates are derived. The mechanism of the instability is related to that of the negative mass instability of charged-particle rings. We propose that the instability may drive a disk toward a state in which f (r) is approximately constant.Values of ..cap omega.. (r), kappa (r), and sigma (r) derived from observations are used to calculate f (r) for two cases: For our Galaxy we find 3.8

• Research Organization: Center for Radiophysics and Space Research, and Department of Applied Physics, Cornell University
• OSTI ID: 6779989
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 221:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANGULAR MOMENTUM
DISTURBANCES
FLUID FLOW
FLUID MECHANICS
GALAXIES
GRAVITATION
HYDRODYNAMICS
HYPOTHESIS
INSTABILITY
MASS
MECHANICS
MOTION
NEGATIVE MASS
ROTATION