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Abstract: Multiple, sequential mergers are unavoidable in the hierarchical build-uppicture of galaxies, in particular for the minor mergers that are frequent andhighly likely to have occured several times for most present-day galaxies.However, the effect of repeated minor mergers on galactic structure andevolution has not been studied systematically so far. We present a numericalstudy of multiple, subsequent, minor galaxy mergers, with various mass ratiosranging from 4:1 to 50:1. The N-body simulations include gas dynamics and starformation. We study the morphological and kinematical properties of theremnants, and show that several so-called -minor- mergers can lead to theformation of elliptical-like galaxies that have global morphological andkinematical properties similar to that observed in real elliptical galaxies.The properties of these systems are compared with those of elliptical galaxiesproduced by the standard scenario of one single major merger. We thus show thatrepeated minor mergers can theoretically form elliptical galaxies without majormergers, and can be more frequent than major mergers, in particular at moderateredshift. This process must then have formed some elliptical galaxies seentoday, and could in particular explain the high boxiness of massiveellipticals, and some fundamental relations observed in ellipticals. Inaddition, because repeated minor mergers, even at high mass ratios, destroydisks into spheroids, these results indicate that spiral galaxies cannot havegrown only by a succession of minor mergers.

Autor: Frederic Bournaud 1, Chanda J. Jog 2, Francoise Combes 3 1AIM, CEA-Saclay 2 IISc Bangalore 3 Observatoire de Paris LERMA


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