On the Mass Assembly History of the Local Group

Abstract

In this work an ensemble of simulated Local Group analogues is used to constrain the properties of the mass assembly history of the Milky Way (MW) and Andromeda (M31) galaxies. These objects have been obtained using the constrained simulation technique, which ensures that simulated LGs live within a large scale environment akin to the observed one. Our results are compared against a standard $\Lambda$ Cold Dark Matter ($\Lambda$CDM) series of simulations which use the same cosmological parameters. This allows us to single out the effects of the constraints on the results. We find that (a) the median constrained merging histories for M31 and MW live above the standard ones at the 1-$\sigma$ level, (b) the median formation time takes place $\approx$ 0.5 Gyr earlier than unconstrained values, while the latest major merger happens on average 1.5 Gyr earlier and (c) the probability for both LG haloes to have experienced their last major merger in the first half of the history of the Universe is $\approx$ 50% higher for the constrained pairs. These results have been estimated to be significant at the 99% confidence level by means of a Kolmogorov-Simirnov test. These results suggest that the particular environment in which the Milky Way and Andromeda form plays a role in shaping their properties, and favours earlier formation and last major merger time values in agreement with other observational and theoretical considerations.

10 pages, 3 figures. Accepted for publication in MNRAS

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Cited by in corpus (10)

• The Hestia project: simulations of the Local Group
• Caught in the cosmic web: Environmental effect on halo concentrations, shape, and spin
• SIBELIUS-DARK: a galaxy catalogue of the Local Volume from a constrained realisation simulation
• The 2MASS redshift survey galaxy group catalogue derived from a graph-theory based friends-of-friends algorithm
• Constraining the Milky Way's Ultraviolet to Infrared SED with Gaussian Process Regression
• Anisotropic satellite accretion onto the Local Group with HESTIA
• Kinematics of the Local Group gas and galaxies in the Hestia simulations
• Hermeian haloes: extreme objects with two interactions in the past
• Build-up and survival of the disc: From numerical models of galaxy formation to the Milky Way
• The Milky Way and M31 Orbital History: Did the Local Group evolve in isolation?