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Clumps and streams in the local dark matter distribution
1University of California, Department of Astronomy and Astrophysics, Santa Cruz, California 95064, USA. diemand@ucolick.org
Nature
|August 8, 2008
Summary
Dark matter simulations reveal numerous surviving subhalos and cold streams within galactic halos. These substructures, matching observed dwarf galaxies, enhance gamma-ray and cosmic ray production, impacting cosmological models.
Area of Science:
- Cosmology
- Astrophysics
- Computational Physics
Background:
- Cosmological structure formation in cold dark matter models involves hierarchical merging of smaller units.
- Previous simulations indicated incomplete merging, with inner halo cores surviving as subhalos.
- Resolving substructure in the inner regions of galactic halos is crucial for understanding dark matter distribution.
Purpose of the Study:
- To investigate dark matter substructure in the inner regions of a simulated Galactic halo.
- To analyze the properties and implications of surviving dark matter clumps (subhalos) and streams.
- To assess the impact of substructure on observable phenomena like dwarf galaxy formation, gravitational lensing, and particle astrophysics signals.
Main Methods:
- Conducted a high-resolution numerical simulation of structure formation in a cold dark matter cosmology.
- Focused on resolving dark matter substructure, including concentrated clumps and streams, within the simulated Galactic halo.
- Compared simulation results with observational data of dwarf satellite galaxies and gravitational lensing phenomena.
Main Results:
- Identified hundreds of concentrated dark matter subhalos near the solar circle and numerous cold streams.
- Revealed the fractal nature of dark matter clustering, with consistent substructure and cusped density profiles in both isolated halos and subhalos.
- Found that subhalo properties match observed faint, dark-matter-dominated dwarf satellite galaxies and can explain anomalous gravitational lensing flux ratios.
- Predicted significant boosts in gamma-ray production (4-15x) from dark matter annihilation and enhanced local cosmic ray production (1.4-10x) due to subhalos.
Conclusions:
- The simulation supports the survival of significant dark matter substructure even in the inner halo.
- Subhalos play a crucial role in explaining the abundance and properties of dwarf satellite galaxies and lensing observations.
- Dark matter substructure substantially enhances astrophysical signals from dark matter annihilation and cosmic ray production.
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