Subhalo accretion through filaments

Abstract

We track subhalo orbits of galaxy and group sized halos in cosmological simulations. We identify filamentary structures around halos and we use these to define a sample of subhalos accreted from filaments as well as a control sample of subhalos accreted from other directions. We use these samples to study differences in satellite orbits produced by filamentary accretion. Our results depend on host halo mass. We find that for low masses, subhalos accreted from filaments show $\sim 10\%$ shorter lifetimes compared to the control sample, they show a tendency towards more radial orbits, reach halo central regions earlier, and are more likely to merge with the host. For higher mass halos this lifetime difference dissipates and even reverses for cluster sized halos. This behavior appears to be connected to the fact that more massive hosts are connected to stronger filaments with higher velocity coherence and density, with slightly more radial subhalo orbits. Because subhalos tend to follow the coherent flow of the filament, it is possible that such thick filaments are enough to shield the subhalo from the effect of dynamical friction at least during their first infall. We also identify subhalo pairs/clumps which merge with one another after accretion. They survive as a clump for only a very short time, which is even shorter for higher subhalo masses, suggesting that the Magellanic Clouds and other Local group satellite associations, may have entered the MW virial radius very recently and probably are in their first infall. Filaments boost the accretion of satellite associations.

Accepted for publication in ApJ

References in corpus (8)

• Are the Magellanic Clouds on their First Passage about the Milky Way?
• Infall of substructures onto a Milky Way-like dark halo
• Satellite Dwarf Galaxies in a Hierarchical Universe: The Prevalence of Dwarf-Dwarf Major Mergers
• Dynamics of the Magellanic Clouds in a LCDM Universe
• The alignment of satellite galaxies and cosmic filaments: observations and simulations
• Satellite Systems around Galaxies in Hydrodynamic Simulations
• On the Segregation of Dark Matter Substructure
• The Local Group in the cosmic web

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