Tidal effects and the environment dependence of halo assembly |
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| Authors: | Oliver Hahn Cristiano Porciani Avishai Dekel C Marcella Carollo |
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| Institution: | Department of Physics, ETH Zurich, 8093 Zurich, Switzerland;Argelander Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany;Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel |
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| Abstract: | We explore a possible origin for the puzzling anti-correlation between the formation epoch of galactic dark-matter haloes and their environment density. This correlation has been revealed from cosmological N -body simulations and is in conflict with the extended Press–Schechter model of halo clustering. Using similar simulations, we first quantify the straightforward association of an early formation epoch with a reduced mass-growth rate at late times. We then find that a primary driver of suppressed growth, by accretion and mergers, is tidal effects dominated by a neighbouring massive halo. The tidal effects range from a slowdown of the assembly of haloes due to the shear along the large-scale filaments that feed the massive halo to actual mass loss in haloes that pass through the massive halo. Using the restricted three-body problem, we show that haloes are prone to tidal mass loss within 1.5 virial radii of a larger halo. Our results suggest that the dependence of the formation epoch on environment density is a secondary effect induced by the enhanced density of haloes in filaments near massive haloes where the tides are strong. Our measures of assembly rate are particularly correlated with the tidal field at high redshifts z ～ 1 . |
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| Keywords: | methods: N-body simulations galaxies: formation galaxies: haloes cosmology: theory dark matter large-scale structure of Universe |
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