Testing the Lambda-Cold Dark Matter model at galactic scales – Niels Bohr Institute - University of Copenhagen

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Testing the Lambda-Cold Dark Matter model at galactic scales

The Lambda-Cold Dark Matter model has gained the place of cosmological paradigm, yet its success at explaining the large-scale universe is not reproduced at galactic scales. This
thesis focus on aspects of testing the cosmological paradigm at galactic scales, by gaining
insights both theoretically and observationally into the dark and baryonic matter distributions
of galaxies.
Nonextensive statistical mechanics, a generalization of classical statistical mechanics
designed to describe long-range interaction systems, have been proposed recently to predict the structure of dark matter halos, using stellar polytropes. A careful comparison of
structural radial profiles of stellar polytropes with those of simulated dark matter halos is
presented in this thesis. It establishes that nonextensive statistical mechanics are unable
to predict the structure of dark matter halos.
Gravitational lensing provides a promising way of constraining the mass distribution of
disk galaxies and measure their mass-to-light ratio. Unfortunately, only seven disk-galaxy
lenses are known to date. Here is presented the first automated spectroscopic search for
disk-galaxy lenses, using the Sloan Digital Sky Survey database. Eight disk-galaxy lens
candidates are studied, using imaging and long-slit spectroscopy observations. Two new
gravitational lenses are presented, which are probable disk and S0 galaxies, as well as four
very interesting disk-galaxy lens candidates, and two probable lenses where the lens galaxy
is either an S0 or elliptical galaxy. Higher resolution observations are needed to further
study these systems. These results open promising perspectives for enlarging the sample
of known disk-galaxy lenses, and gaining further understanding of the baryonic and dark
matter distributions in disk galaxies.


Link to thesis here