Formation of Elliptical Galaxies by Collisionless Equal and Unequal Mass Mergers

We performed a large set of collisionless N-body simulations of merging diskgalaxies with mass ratios of 1:1, 2:1, 3:1, and 4:1 using the special purpose hardware GRAPE. These simulations were used to examine whether the formation of elliptical galaxies can be explained in the context of the merger scenario. The photometric, kinematical and isophotal properties of the simulated merger remnants were investigated. The methods used to determine the characteristic properties were developed to resemble the methods used for observations of giant elliptical galaxies. We took projection effects into account and analysed the remnant properties in a statistical way for comparison with observations. We found that 1:1 merger remnants rotate slowly, are supported by anisotropic velocity dispersions, have significant minor-axis rotation, and show predominantly boxy isophotes in good agreement with observations of bright giant ellipticals. 3:1 and 4:1 remnants are isotropic, fast rotators, show a small amount of minor-axis rotation, and have disky isophotes in perfect agreement with observations of faint fast rotating giant elliptical galaxies. 2:1 remnants show intermediate properties. Projection effects lead to a large spread in the data in good agreement with observations. They do not change the fundamental differences between equal-mass and unequal-mass merger remnants. Subject headings: galaxies: interaction– galaxies: structure – galaxies: evolution – methods: numerical