Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20912902b&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #129.02; Bulletin of the American Astronomical Society,
Mathematics
Logic
Scientific paper
The far future provides an excellent laboratory for studying cosmological structures. The eventual dominance of the cosmological constant causes the universe to enter a phase of exponential deSitter expansion during which dark matter halos are allowed to relax without interruptions from mass accretion. Using of suite of N-body simulations evolved to scale factor a = 100 in an ΛCDM universe, I present the equilibrium structure of halos and investigate the importance of mergers in setting this structure. Halos in equilibrium have a greatly simplified radial phase space profile characterized by a single zero-velocity surface that unambiguously defines the halo edge. The radial density profile for such halos is well fit by an NFW profile internal to r200, but is to shallow at larger radii and better fit by a truncated Hernquist profile. In order to study the importance of hierarchical merging in setting the equilibrium structure, I also present results form ΛWDM-like simulations with initial power spectra that suppress the early formation of small halos. Using these simulations, I present a modified fit to the mass accretion of Wechsler et al. (2002) that better characterizes halo growth at all epochs. At the end of the simulations, we recover density profiles and phase space structures that are virtually unchanged between the CDM and WDM cosmologies. A systematic concentration shift can be characterized in terms of the halo formation epoch, ac. Once substructure effects are removed the phase space distributions are equally unchanged.
Adams Fred C.
Busha Michael T.
Evrard August E.
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