Merging encounters between equal-mass non-rotating galaxies

Abstract

N-body simulations are used to investigate merging encounters between equal-mass isotropic non-rotating de Vaucouleurs-type galaxies, in order to obtain empirical correlations relating the structural parameters of merger remnants to the initial orbit and structure of the progenitors. We found that these parameters correlate well with the orbital energy of the pair. The angular momentum of the orbit was found to influence noticeably only the internal spin of the remnant. An analysis of the locations of the remnants in the Reff - μeff plane (Reff and μeff stand for the effective radius and the logarithm of the surface density measured at Reff), relative to that of the progenitor, suggests that galaxies which have experienced several mergers in the past would be shifted respect to the Reff-μeff relation holding for normal elliptical galaxies. Such a shift might be consistent with data on the properties of brightest cluster members recently published by Schomber (1987). The density structure of the remnants of merging collisions between de Vaucouleurs galaxy models progressively approaches a de Vaucoulers profile. Transitory "light" excess in the outer parts, as found by Aguilar and White (1986) for non-merging encounters, are also produced. This suggests that some "tidally distended" galaxies (Kormendy 1977) may be actually interpreted as a merger between galaxies of comparable mass and size on its later stages.