Estimation of the components of galaxies using N-body simulations

Abstract

Abstract Direct numerical N-body simulation was applied to four spiral galaxies (NGC 6503, NGC 3198, NGC 891 and NGC 1566), for which the rotation curves, radial scalelengths L and radial distribution of stellar velocity dispersion of the discs are known. Models contained three-dimensional collisionless disc and ‘rigid’ spherical components (bulge and halo), the total relative mass u of which was considered as a free parameter which varied from one model to another. The initial velocity dispersion was chosen at a sub-critical level for gravitational instability. It was assumed that the observed velocity dispersion of disc stars at a given radius must be equal or (in the general case) not less than the calculated one (projected onto the line-of-sight) for a given galaxy after the initially unstable model disc heats up to a steady condition. A comparison of simulated stellar velocity dispersion and rotation curves of galaxies with the observed ones favors the ‘light disc’ solution: μ ≥ 2 within the radius r = 4L.