On the global structure of self-gravitating discs for softened gravity

• Published in: Monthly notices of the Royal Astronomical Society Vol. 294; no. 3; pp. 485 - 488
• Main Authors: Sommer-Larsen, Jesper, Vedel, Henrik, Hellsten, Uffe
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Science Ltd 01.03.1998
• Subjects: galaxies: kinematics and dynamics; galaxies: structure; gravitation; methods: numerical
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1046/j.1365-8711.1998.01336.x

The effects of gravitational softening on the global structure of self‐gravitating discs in centrifugal equilibrium are examined in relation to hydrodynamical/gravitational simulations. The one‐parameter spline softening proposed by Hernquist & Katz is used. It is found that if the characteristic size of a disc, r, is comparable to or less than the gravitational softening length, ε, then the cross‐section of the simulated disc is significantly larger than that of a no‐softening (Newtonian) disc with the same mass and angular momentum. We demonstrate, furthermore, that if r≲ε/2 then the scaling relation r∝ε3/4 holds for a given mass and specific angular momentum distribution with mass. Finally, we compare some of the theoretical results obtained in this paper and a previous one with the results of numerical Tree‐SPH simulations and find qualitative agreement.