Mathematics
Scientific paper
Jun 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003phdt.........1k&link_type=abstract
PhD Thesis, Combined Faculties for the Natural Sciences and for Mathematics of the Ruperto-Carola University, Germany for the de
Mathematics
1
Elliptical Galaxies, Origin, Structure, Galaxy Mergers
Scientific paper
The formation of elliptical galaxies by merging galaxies has been investigated adopting three different paths. First, we confirm that the frequency of major merger events predicted by hierarchical models is in fair agreement with observations. Second, the generally assumed initial conditions used in numerical simulations of merging galaxies were tested. Orbital parameters of the merging galaxies are derived self-consistently from large scale N-body simulations, showing that the commonly used parameters are in agreement, but resemble just a small fraction of the possible parameter space. Most of the mergers are taking place on parabolic orbits with pericenter distances larger than generally assumed in simulations. Using semi-analytical modeling techniques, the morphology of progenitors is found to be dependent on the luminosity of the present-day elliptical. One can distinguish three different regions: ellipticals with MB <~ -21 are mainly formed by a merger of two bulge-dominated galaxies, while ellipticals with roughly MB ~ -20 are mainly the result of a disk-dominated galaxy merging with a bulge-dominated galaxy. Only low luminous ellipticals with MB >~ -18 are the product of disk galaxies merging, as usually assumed in merger simulations. The third path is to implement results of detailed numerical simulations into a semi-analytic model of galaxy formation model and to compare global predictions for ellipticals with observations. The dependence of the isophotal shape of an elliptical on the mass ratio of the last major merger, as suggested by dissipationless simulations, fails in reproducing the observed correlation between isophotal shape and mass of an elliptical. Only the assumption that all major mergers between elliptical galaxies lead to boxy ellipticals allows to recover the observed trend. Including the effects of binary black hole merging in the centers of the remnants, it is possible to recover the observed core mass deficit-black hole mass relation.
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