The Antennae Galaxies

The Antennae galaxies (NGC 4038/39) are the nearest and
best-studied major merger of two gas-rich spirals in the local
Universe. They are named after the characteristic pair of tidal
tails that protrude out of their main galactic disks. Due to their
proximity the Antennae are extremely well sampled by modern
high-resolution observations over an enormous wavelength range,
from radio to X-ray. This allows for a comprehensive
multiwavelength approach to the present-day morphology and
dynamical history of the system. The goal of this Thesis is to test
the available high-quality multiwavelength data against new
high-resolution merger simulations as a key to improve our
understanding of several merger-induced physical processes, such as
starbursts and the formation of young star clusters. These
processes are expected to have been even more important in the
formation and early evolution of galaxies. First of all, accurate
initial conditions for the interaction orbit and the initial galaxy
models need to be constrained. To this end, we perform an extended
parameter search in order to obtain a suitable match to the
Antennae galaxies. Using these new initial conditions, we are able
to present the first high-resolution numerical simulations that
successfully match the detailed large- and small-scale morphology
and kinematics of the Antennae galaxies. Moreover, the spatial
distribution of star-forming regions as well as the total star
formation rate are reproduced in excellent quantitative agreement,
in particular, if we adopt a very weak stellar feedback. We find
that the Antennae are currently in a special phase of their
evolution, shortly after the second pericenter. They will merge
soon within the next ~50 Myr. In addition, we compare the star
formation histories of all published hydrodynamical Antennae
simulations with the observed cluster age distribution. The latter
is well approximated by a power-law dN/dt ~ t^gamma, declining as
gamma = 1. Under the assumption that clusters form at rates
proportional to the total star formation, it is found that the
variations in the simulated formation histories alone cannot
account for most of the steep decline in the observed age
distribution. This provides strong evidence for efficient,
prolonged cluster disruption in the Antennae, similar to more
quiescent galaxies. Finally, we address the question of whether the
Antennae will evolve into a typical elliptical galaxy. We find that
the virialized merger remnant resembles an oblate, fast-rotating
early-type with surface brightness profile well fitted by a Sersic
function of index n ~ 5. For high metallicities (Z > Z_sun) the
stellar remnant of the Antennae may add to a population of
present-day ellipticals after secular evolution of another ~2.5 -3
Gyr. Within this Thesis, we present an improved numerical model for
the interacting Antennae galaxies that may serve as a test-bed for
further investigations of this archetypal merger. As next steps, we
plan to investigate the extended hot gas component found in X-ray
observations of the Antennae, and test our present results in a
code comparison project.