Reconciling Dwarf Galaxies With Λcdm Cosmology: Simulating a Realistic Population of Satellites Around a Milky Way–mass Galaxy

Abstract

Low-mass "dwarf" galaxies represent the most significant challenges to the cold dark matter (CDM) model of cosmological structure formation. Because these faint galaxies are (best) observed within the Local Group (LG) of the Milky Way (MW) and Andromeda (M31), understanding their formation in such an environment is critical. We present first results from the Latte Project: the Milky Way on FIRE (Feedback in Realistic Environments). This simulation models the formation of a MW-mass galaxy to z = 0 within ΛCDM cosmology, including dark matter, gas, and stars at unprecedented resolution: baryon particle mass of 7070 M with gas kernel/softening that adapts down to 1 pc (with a median of 25 − 60 pc at z = 0). Latte was simulated using the GIZMO code with a mesh-free method for accurate hydrodynamics and the FIRE-2 model for star formation and explicit feedback within a multi-phase interstellar medium. For the first time, Latte self-consistently resolves the spatial scales corresponding to half-light radii of dwarf galaxies that form around a MW-mass host down to M star 10 5 M . Latte's population of dwarf galaxies agrees with the LG across a broad range of properties: (1) distributions of stellar masses and stellar velocity dispersions (dynamical masses), including their joint relation; (2) the mass-metallicity relation; and (3) a diverse range of star-formation histories, including their mass dependence. Thus, Latte produces a realistic population of dwarf galaxies at M star 10 5 M that does not suffer from the "missing satellites" or "too big to fail" problems of small-scale structure formation. We conclude that baryonic physics can reconcile observed dwarf galaxies with standard ΛCDM cosmology.

A Rogues’ Gallery of Andromeda's Dwarf Galaxies. I. A Predominance of Red Horizontal Branches

“…Variations in the evolutionary histories of M31 and MW satellites extend far beyond the history of two Local Group sub-systems. Indeed, these faint galaxies play important roles from calibrating physics in detailed simulations to testing ΛCDM models of galaxy formation (e.g., Wetzel et al 2016) to constraining the shape of the faint end of the high-redshift galaxy luminosity function (e.g., Boylan-Kolchin et al 2015;Weisz & Boylan-Kolchin 2017). However, most of our detailed understanding of dwarf galaxies currently stems from a small number of systems around the MW and one should be wary of mistaking the details of a specific system, on a specific orbit, around a specific host, for the global properties of dwarf galaxies in a group environment.…”

“…Due to their close proximity, the bulk of observational efforts have been aimed at satellites of the Milky Way (MW). Thus, our broad understanding of low-mass galaxies, including star formation histories, chemical evolution, dark matter content, and their use as benchmarks for cosmological simulations, are based on a set of galaxies that reside in a common galactic ecosystem (e.g., Simon & Geha 2007;Tolstoy et al 2009;Kirby et al 2011;Boylan-Kolchin et al 2012;Brooks et al 2013;Brown et al 2014;Weisz et al 2014a;Wetzel et al 2016). It remains unknown how well the MW satellite population reflects the general properties of low-mass spheroidal satellites, let alone low-mass galaxies in general.…”

Core-halo mass relation of ultralight axion dark matter from merger history

“…However, as discussed in [18], to get more consistent constraints we need to consider details of the interplay between FDM and baryonic physics. The baryonic feedback may help reconcile the tension between different observations [33].…”

Under pressure: quenching star formation in low-mass satellite galaxies via stripping

“…High-resolution hydrodynamic simulations of Milky Way-or Local Group-like environments should provide a robust means for studying the possible importance of feedback in increasing the efficiency of stripping (e.g. Zolotov et al 2012;Mistani et al 2016;Wetzel et al 2016;Garrison-Kimmel et al in prep).…”