The dark matter assembly of the Local Group in constrained cosmological simulations of a Λ cold dark matter universe
EntityUAM. Departamento de Física Teórica
PublisherOxford University Press; Royal Astronomical Society
10.1111/j.1365-2966.2011.19358.xMonthly Notices of the Royal Astronomical Society 417.2 (2011):1434-1443
ISSN0035-8711 (print); 1365-2966 (online)
Funded byGY would like to thank the MICINN (Spain) for financial support under project numbers FPA 2009-08958, AYA 2009-13875-C03 and the SyeC Consolider project CSD 2007-0050
SubjectsCosmology: theory; Galaxies: haloes; Galaxy: formation; Local Group; Física
NoteThis article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2011 RAS © 2011 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Rights© 2011 The Authors; © 2011 RAS
We make detailed theoretical predictions for the assembly properties of the Local Group (LG) in the standard Λ cold dark matter cosmological model. We use three cosmological N-body dark matter simulations from the Constrained Local Universe Simulations project, which are designed to reproduce the main dynamical features of the matter distribution down to the scale of a few Mpc around the LG. Additionally, we use the results of an unconstrained simulation with a 60 times larger volume to calibrate the influence of cosmic variance. We characterize the mass aggregation history (MAH) for each halo by three characteristic times: the formation, assembly and last major merger times. A major merger is defined by a minimal mass ratio of 10: 1. We find that the three LGs share a similar MAH with formation and last major merger epochs placed on average ≈10-12 Gyr ago. Between 12 and 17 per cent of the haloes in the mass range 5 × 10 11 < M h < 5 × 10 12h -1M ⊙ have a similar MAH. In a set of pairs of haloes within the same mass range, a fraction of 1-3 per cent share similar formation properties as both haloes in the simulated LG. An unsolved question posed by our results is the dynamical origin of the MAH of the LGs. The isolation criteria commonly used to define LG-like haloes in unconstrained simulations do not narrow down the halo population into a set with quiet MAHs, nor does a further constraint to reside in a low-density environment. The quiet MAH of the LGs provides a favourable environment for the formation of disc galaxies like the Milky Way and M31. The timing for the beginning of the last major merger in the Milky Way dark matter halo matches with the gas-rich merger origin for the thick component in the galactic disc. Our results support the view that the specific large- and mid-scale environments around the LG play a critical role in shaping its MAH and hence its baryonic structure at present
Google Scholar:Forero-Romero, Jaime E. - Hoffman, Yehuda - Yepes Alonso, Gustavo - Gottlöber, Stefan - Piontek, Robert - Klypin, Anatoly - Steinmetz, Matthias
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