Small Scale Problems of the ΛCDM Model: A Short Review

Popolo, A. Del; Delliou, Morgan Le

doi:10.3390/galaxies5010017

Cited by 266 publications

(193 citation statements)

References 406 publications

(814 reference statements)

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“…There are many recent reviews or overview papers that cover, in more depth, certain aspects of this review. These include Frenk & White (2012), Peebles (2012), and Primack (2012) on the historical context of ΛCDM and some of its basic predictions; Willman (2010) and McConnachie (2012) on searches for and observed properties of dwarf galaxies in the Local Group; Feng (2010), Porter, Johnson &Graham (2011), andStrigari (2013) on the nature of and searches for dark matter; Kuhlen, Vogelsberger & Angulo (2012) on numerical simulations of cosmological structure formation; and Brooks (2014), Weinberg et al (2015) and Del Popolo & Le Delliou (2017) on small-scale issues in ΛCDM. Additionally, we will not discuss cosmic acceleration (the Λ in ΛCDM) here; that topic is reviewed in Weinberg et al (2013).…”

Section: Introductionmentioning

confidence: 99%

Small-Scale Challenges to the ΛCDM Paradigm

Bullock

Boylan-Kolchin

2017

Annu. Rev. Astron. Astrophys.

1,366

1,017

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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 Universe and its evolution with time. Yet on length scales smaller than ∼ 1 Mpc and mass scales smaller than ∼ 10 11 M , 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 will be required to meet these challenges. Other anomalies, including the observed planar and orbital configurations of Local Group satellites and the tight baryonic/dark matter scaling relations obeyed by the galaxy population, have been less thoroughly explored in the context of ΛCDM theory. Future surveys to discover faint, distant dwarf galaxies and to precisely measure their masses and density structure hold promising avenues for testing possible solutions to the small-scale challenges going forward. Observational programs to constrain or discover and characterize the number of truly dark low-mass halos are among the most important, and achievable, goals in this field over then next decade. These efforts will either further verify the ΛCDM paradigm or demand a substantial revision in our understanding of the nature of dark matter.

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Section: Introductionmentioning

confidence: 99%

Small-Scale Challenges to the ΛCDM Paradigm

Bullock

Boylan-Kolchin

2017

Annu. Rev. Astron. Astrophys.

1,366

1,017

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“…One important feature of such a scenario is suppression of structure formation on small scales due to the uncertainty principle, where the characteristic scales below which structure formation is suppressed are determined by the nature of ψDM such as its mass (see [13] and references therein). Possibilities of ψDM have recently attracted increasing attention partly because more and more tight experimental limits have been obtained on popular DM candidates such as weakly-interacting-massive particles [15], and also because ψDM has the potential to help alleviate or solve the ΛCDM small-scale crisis [16].…”

Section: Quantifying Star Formation Historymentioning

confidence: 99%

Gravitational waves from binary black holes as probes of the structure formation history

Nakama

2020

Physics of the Dark Universe

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Gravitational-wave detectors on earth have detected gravitational waves from merging compact objects in the local Universe. In future we will detect gravitational waves from higher-redshift sources, which trace the high-redshift structure formation history. That is, by observing high-redshift gravitational-wave events we will be able to probe structure formation history. This will provide additional insight into the early Universe when primordial fluctuations are generated and also into the nature of dark matter.

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“…Understanding the nature of dark matter is one of the most significant challenges in the 21st century for both physicists and astrophysicists. While the cold dark matter (CDM) paradigm has been the most popular model of dark matter, observational tensions on the galactic scale (Bullock & Boylan-Kolchin 2017;Del Popolo & Le Delliou 2017) and non-detection of dark matter particles in the ground-based experiments have led scientists to examine alternative possibilities. Part of the reason why it is difficult to probe the nature of dark matter is that (as far as we can tell) it only interacts with ordinary matter via gravity; only affecting astrophysical observations on very large scales ( few kpc).…”

Section: Introductionmentioning

confidence: 99%

Gravitational potential from small-scale clustering in action space: application to Gaia Data Release 2

Yang

Boruah

Afshordi

2020

Monthly Notices of the Royal Astronomical Society

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Most measurements of mass in Astronomy that use kinematics of stars or gas rely on assumptions of equilibrium that are often hard to verify. Instead, we develop a novel idea that uses the clustering in action space, as a probe of underlying gravitational potential: the correct potential should maximize small-scale clustering in the action space. We provide a first-principle derivation of likelihood using the two-point correlation function in action space, and test it against simulations of stellar streams. We then apply this method to the 2nd data release of Gaia, and use it to measure the radial force fraction f h and logarithmic slope α of dark matter halo profile. We investigate stars within 9-11 kpc and 11.5-15 kpc from Galactic centre, and find ( f h , α) = (0.391 ± 0.009, 1.835 ± 0.092) and (0.351 ± 0.012, 1.687 ± 0.079), respectively. We also confirm that the set of parameters that maximize the likelihood function do correspond to the most clustering in the action space. The best-fit circular velocity curve for Milky Way potential is consistent with past measurements (although it is ∼ 5-10% lower than previous methods that use masers or globular clusters).Our work provides a clear demonstration of the full statistical power that lies in the full phase space information, relieving the need for ad hoc assumptions such as virial equilibrium, circular motion, or steam-finding algorithms.

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Small Scale Problems of the ΛCDM Model: A Short Review

Cited by 266 publications

References 406 publications

Small-Scale Challenges to the ΛCDM Paradigm

Small-Scale Challenges to the ΛCDM Paradigm

Gravitational waves from binary black holes as probes of the structure formation history

Gravitational potential from small-scale clustering in action space: application to Gaia Data Release 2

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