Dark matter–radiation interactions: the impact on dark matter haloes

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTIn the thermal dark matter (DM) paradigm, primordial interactions between DM and Standard Model particles are responsible for the observed DM relic density. In Boehm et al. (2014), we showed that weak-strength interactions between DM and radiation (photons or neutrinos) can erase smallscale density fluctuations, leading to a suppression of the matter power spectrum compared to the collisionless cold DM (CDM) model. This results in fewer DM subhaloes within Milky Way-like DM haloes, implying a reduction in the abundance of satellite galaxies. Here we use very high resolution N -body simulations to measure the dynamics of these subhaloes. We find that when interactions are included, the largest subhaloes are less concentrated than their counterparts in the collisionless CDM model and have rotation curves that match observational data, providing a new solution to the "too big to fail" problem.

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“…Alternatively, one can interpret this as a lower central density or concentration for the haloes in γCDM, as seen in Schewtschenko et al (2015).…”

Section: Resultsmentioning

confidence: 99%

“…These criteria are more restrictive than those employed in our earlier work on the structure of haloes (Schewtschenko et al 2015) as they also take into account the internal kinematics of the LG. We obtain four LG candidates and therefore, eight MW-like haloes.…”

Section: Simulationsmentioning

confidence: 99%

Dark matter–radiation interactions: the structure of Milky Way satellite galaxies

Schewtschenko

Baugh

Wilkinson

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Combined with an expected increase in the number of satellites from additional completeness corrections, this would lead to even stricter constraints on the interaction cross section. A future paper will present the non-linear structure formation for such models in greater depth to examine whether one can solve the other small-scale problems of CDM (Schewtschenko et al 2014).…”

Section: Discussionmentioning

confidence: 99%

“…We will use these results to extract constraints on the DM-photon scattering cross section. The other small-scale problems of CDM will be addressed in forthcoming work (Schewtschenko et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Using the Milky Way satellites to study interactions between cold dark matter and radiation

Bœhm¹,

Schewtschenko²,

Wilkinson³

et al. 2014

Monthly Notices of the Royal Astronomical Society: Letters

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120

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The cold dark matter (CDM) model faces persistent challenges on small scales. In particular, taken at face value, the model significantly overestimates the number of satellite galaxies around the Milky Way. Attempts to solve this problem remain open to debate and have even led some to abandon CDM altogether. However, current simulations are limited by the assumption that dark matter feels only gravity. Here, we show that including interactions between CDM and radiation (photons or neutrinos) leads to a dramatic reduction in the number of satellite galaxies, alleviating the Milky Way satellite problem and indicating that physics beyond gravity may be essential to make accurate predictions of structure formation on small scales. The methodology introduced here gives constraints on dark matter interactions that are significantly improved over those from the cosmic microwave background.

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“…4.2), and this has in fact been the initial motivation for introducing SIDM models [350]. Although the extra damping (through selfinteraction [351] or collisions with standard particles such as radiation [352]) is a feature of various dark matter models, the existing large-scale structure constraints so far favor no observable deviations from the standard cold dark matter picture. Such deviations on very small scales may however be observable in the CMB [353], and can be looked for using future small-scale CMB experiments.…”

Section: New Particles and Structure Formationmentioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

459

210

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Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.Keywords: cosmology -dark energy -cosmological constant problem -modified gravitydark matter -early universe Cosmology has been both blessed and cursed by the establishment of a standard model: ΛCDM. On the one hand, the model has turned out to be extremely predictive, explanatory, and observationally robust, providing us with a substantial understanding of the formation of large-scale structure, the state of the early Universe, and the cosmic abundance of different types of matter and energy. It has also survived an impressive battery of precision observational tests -anomalies are few and far between, and their significance is contentious where they do arise -and its predictions are continually being vindicated through the discovery of new effects (B-mode polarization [1] and lensing [2,3] of the cosmic microwave background (CMB), and the kinetic Sunyaev-Zel'dovich effect [4] being some recent examples). These are the hallmarks of a good and valuable physical theory.On the other hand, the model suffers from profound theoretical difficulties. The two largest contributions to the energy content at late times -cold dark matter (CDM) and the cosmological constant (Λ) -have entirely mysterious physical origins. CDM has so far evaded direct detection by laboratory experiments, and so the particle field responsible for it -presumably a manifestation of "beyond the standard model" particle physics -is unknown. Curious discrepancies also appear to exist between the predicted clustering properties of CDM on small scales and observations. The cosmological constant is even more puzzling, giving rise to quite simply the biggest problem in all of fundamental physics: the question of why Λ appears to take such an unnatural value [5,6,7]. Inflation, the theory of the very early Universe, has also been criticized for being fine-tuned and under-predictive [8], and appears to leave many problems either unsolved or fundamentally unresolvable. These problems are indicative of a crisis.From January 14th-17th 2015, we held a conference in Oslo, Norway to surve...

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Dark matter–radiation interactions: the impact on dark matter haloes

Cited by 75 publications

References 52 publications

Dark matter–radiation interactions: the structure of Milky Way satellite galaxies

Dark matter–radiation interactions: the structure of Milky Way satellite galaxies

Using the Milky Way satellites to study interactions between cold dark matter and radiation

BeyondΛCDM: Problems, solutions, and the road ahead

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