Small-Scale Challenges to the ΛCDM Paradigm

By James S. Bullock, M. Boylan-Kolchin. 2017

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The dark energy plus cold dark matter (ΛCDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of the Universe and its evolution with time. Yet on length scales smaller than ∼1 Mpc and mass scales smaller than ∼1011M⊙, the theory faces a number of challenges. For example, the observed cores of many dark matter–dominated galaxies are both less dense and less cuspy than naively predicted in ΛCDM. The number of small galaxies and dwarf satellites in the Local Group is also far below the predicted count of low-mass dark matter halos and subhalos within similar volumes. These issues underlie the most well-documented problems with ΛCDM: cusp/core, missing satellites, and too-big-to-fail. The key question is whether a better understanding of baryon physics, dark matter physics, or both is required to meet these challenges. Other anomalies, including the observed planar and orbital configurations of Local Group satellites and the tight baryonic...

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/e3db770c0d6bc603b4aac88f2f9e9b0cd84178a0

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Citations in the corpus

Disruption of Dark Matter Substructure: Fact or Fiction? (2017, background): “Over the years, though, it has become clear that this ‘missing satellite problem’ is mainly a manifestation of poorly understood baryonic physics related to galaxy formation (see Bullock & Boylan-Kolchin 2017, for a review).”
Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 (2019, background): “…& Peek 2018; Graus et al. 2019; Katz et al. 2019), and the nature of dark matter (e.g., Bergström et al. 1998; Spekkens et al. 2013; Malyshev et al. 2014; Ackermann et al. 2015; Geringer-Sameth et al. 2015; Bullock & Boylan-Kolchin 2017; Clesse & Garćıa-Bellido 2018; Nadler et al. 2019a).”
The milky way total mass profile as inferred from Gaia DR2 (2019, methodology): “The wealth of data available for the Milky Way (MW) makes our galaxy an unmatched laboratory for testing cosmology on the smallest scales and for understanding galaxy formation physics in detail (e.g. see the reviews by Bullock & Boylan-Kolchin 2017; Zavala & Frenk 2019).”
DarkSUSY 6: an advanced tool to compute dark matter properties numerically (2018, background): “In fact, it has been pointed out [55, 79–85] that self-interacting DM (SIDM) could address the most pressing potential small-scale problems of ΛCDM cosmology [86], referred to as ‘core-vs.”
The Local Group on FIRE: dwarf galaxy populations across a suite of hydrodynamic simulations (2018, methodology): “While CDM reproduces large-scale observations extraordinarily well (e.g. Springel et al. 2005), explaining the dwarf galaxy population within the CDM framework has historically proven difficult (see Bullock & Boylan-Kolchin 2017, for a recent review).”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, background): “The red shaded region in the bottom panel gives the range of mass ratios for which feedback is effective in producing a cored dark matter profile (Bullock & Boylan-Kolchin 2017).”
Revisiting constraints on asteroid-mass primordial black holes as dark matter candidates (2019, background): “[108]); it is thus clear that only a tiny fraction of stars would have captured a PBH in this environment, even if PBHs make up all of the dark matter.”
CMB-S4 Science Case, Reference Design, and Project Plan (2019, background): “They can also naturally arise in the context of self-interacting DM, which has been proposed to address possible anomalies on subgalactic scales [292].”