Die Entstehungsgeschichte der dichten Kerne von CDM-Halos; The formation history of the dense cores of CDM-halos

Details Die Entstehungsgeschichte der dichten Kerne von CDM-Halos; The formation history of the dense cores of CDM-halos Die Entstehungsgeschichte der dichten Kerne von CDM-Halos; The formation history of the dense cores of CDM-halos

Jun 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt.........1h&link_type=abstract

PhD Thesis, Naturwissenschaftlich-Mathematische Gesamtfakultät der Universität Heidelberg, Germany. II+122 p. (2001)

Mathematics

Logic

Cosmology, Dark Matter, Galactic Halos

Scientific paper

Concerning the central structure of dark matter halos, there are inconsistent statements coming from numerical simulations and observations of galactic rotation curves. While theoretical work finds singular density profiles ρ(r) ~ r-α with α >= 1 near the center, observations argue for central regions with constant densities. Various attempts on the part of theory to reproduce the observed structure by modified models of halo formation and evolution have failed until now. The aim of the present work is to investigate the effect of a locally restricted modification of the cosmological initial conditions on the structure of dark halos at z = 0, using cosmological N-body simulations. For this purpose a series of simulations has been carried out using an already available hierarchical Treecode - which was extended to treat comoving coordinates - and the special purpose hardware GRAPE. As it turns out, the matter which occupies the halo centers always originates from primordial regions of local maximum density. This is valid for halos suffering a number of "equal mass mergers" during their formation as well as for those which form primarily by the dynamically less complex process of continuous accretion. The simulations were repeated under identical conditions for a randomly chosen number of halos of either class with only the velocity vectors of the "core matter" arbitrarily modified. We find that such a local modification of the initial conditions does not noticeably affect the inner structure of dark halos. The effectiveness of "violent relaxation" is obviously high enough to produce the universal numerical density profile. Hence, a solution to the density problem to the halo centers is unreachable this way.

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