Dark Matter Substructure and Dwarf Galactic Satellites

Figure 1

Formation of a Milky Way-sized dark matter halo in a cosmological simulation of flat ΛCDM cosmology (Ω_m=1−Ω_Λ=0.3, ℎ=0.7, 𝜎₈=0.9). The panels show an evolutionary sequence at nine redshifts (from left to right and from top to bottom) focusing on the most massive progenitor of the main halo at each epoch (redshift of each epoch is shown in the left upper corner). The rendering shows the dark matter particles with intensity indicating the local matter density on a logarithmic stretch. The build-up of the halo proceeds through a series of spectacular mergers, particularly frequent in the early stages of evolution. Many of the merging clumps survive until the present epoch (𝑧=0) in the form of “substructure.’’ The size of the region shown is about 3 comoving Mpc at 𝑧=15, monotonically zooming in to a scale of ≈1 comoving Mpc across at 𝑧=0.

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