Formation of Boxy and Disky Elliptical Galaxies in Early Dissipative Mergers

Abstract

We numerically study the dynamical evolution of mergers of gas-rich galaxies, with special emphasis on the effects of star formation upon the appearance of the isophotal shape of the remnant. We find that the rapidity of gas consumption by star formation greatly affects the isophotal shapes of merger remnants. Mergers with gradual star formation are more likely to form elliptical galaxies with disky isophotes, and those with rapid star formation are more likely to form ellipticals that appear to be both boxy and disky depending on the viewing angle of the observer. We furthermore find that both the radial density profile and the compactness of the core of the merger remnant depend on the rapidity of gas consumption by star formation. Our numerical results imply that the isophotal shapes clearly reflect a difference in the history of star formation of elliptical galaxies at the epoch of their formation.