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Under the sword of Damocles: plausible regeneration of dark matter cusps at the smallest galactic scales

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)L90-L94
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume449
Issue number1
DOIs
Publication statusPublished - 1 Apr 2015

Abstract

We study the evolution of the dark matter (DM) halo profiles of dwarf galaxies driven by the accretion of DM substructures through controlled N-body experiments. Our initial conditions assume that early supernova feedback erases the primordial DM cusps of haloes with z = 0 masses of 10(9) - 10(10) M-aS (TM). The orbits and masses of the infalling substructures are borrowed from the Aquarius cosmological simulations. Our experiments show that a fraction of haloes that undergo 1:3 down to 1:30 mergers are susceptible to reform a DM cusp by z a parts per thousand 0. Cusp regrowth is driven by the accretion of DM substructures that are dense enough to reach the central regions of the main halo before being tidally disrupted. The infall of substructures on the mean of the reported mass-concentration relation and a mass ratio above 1:6 systematically leads to cusp regrowth. Substructures with 1:6-1:8, and 1:8-1:30 only reform DM cusps if their densities are 1 sigma and 2 sigma above the mean, respectively. The merging time-scales of these dense, low-mass substructures is relatively long (5 - 11 Gyr), which may pose a time-scale problem for the longevity of DM cores in dwarfs galaxies and possibly explain the existence of dense dwarfs-like Draco. These results suggest that within cold dark matter a non-negligible level of scatter in the mass profiles of galactic haloes acted on by feedback is to be expected given the stochastic mass accretion histories of low-mass haloes and the diverse star formation histories observed in the Local Group dwarfs.

    Research areas

  • galaxies: dwarf, galaxies: evolution, galaxies: formation, STAR-FORMATION HISTORIES, DWARF GALAXIES, LOCAL GROUP, HALO CONCENTRATIONS, CORES, PROFILES, STELLAR, SUBSTRUCTURE, REIONIZATION, SIMULATIONS

ID: 21459600