Stability of Non-radial Modes and Star Formation in the Galactic Dark Matter Field

Author: Salome Mtchedlidze
Keywords: Jeans instability, dark matter, star formation
Annotation:

Gravitational stability of the compressible isothermal media is studied in the asymmetric gravitational field of the galactic dark matter. For this purpose we expand density of the stellar matter and gravitational potential into spherical harmonics and study the linear stability criteria of the non-radial modes.  We derive the dispersion equation of the non-radial modes in general case. Assuming marginal gravitational stability of spherically symmetric state we derive the stability criteria for higher order multipoles.   We have shown the link between the spherical harmonics of the dark matter potential and spherical harmonics of the observed baryonic density for the non-radial modes that are unstable to the Jeans mechanics. It seems that the dark matter asymmetry that can be described using a single spherical harmonic can be linked with a sum of the higher order spherical harmonics of the observed matter distribution. Hence, any asymmetry of the baryonic matter, e.g. asymmetry of the stellar mass distribution in a galaxy can be linked to the dark matter halo asymmetry modifying the Jeans mass criterion locally.     The problem can be used to analyze the dynamics of star formation in galaxies, where local gravitational stability is significantly modified by the cold dark matter halo of the galaxy. On the other hand, any anisotropy of the stellar mass distribution can constrain dark matter halo properties that strongly differ for the different dark matter candidates.