The impact of inelastic self-interacting dark matter on the dark matter structure of a Milky Way halo

Abstract We study the effects of inelastic dark matter self-interactions on the internal structure of a simulated Milky Way (MW)-size halo. Self-interacting dark matter (SIDM) is an alternative to collisionless cold dark matter (CDM) which offers a unique solution to the problems encountered with CDM on sub-galactic scales. Although previous SIDM simulations have mainly considered elastic collisions, theoretical considerations motivate the existence of multi-state dark matter where transitions from the excited to the ground state are exothermic. In this work, we consider a self-interacting, two-state dark matter model with inelastic collisions, implemented in the Arepo code. We find that energy injection from inelastic self-interactions reduces the central density of the MW halo in a shorter timescale relative to the elastic scale, resulting in a larger core size. Inelastic collisions also isotropize the orbits, resulting in an overall lower velocity anisotropy for the inelastic MW halo. In the inner halo, the inelastic SIDM case (minor-to-major axis ratio s ≡ c/a ≈ 0.65) is more spherical than the CDM (s ≈ 0.4), but less spherical than the elastic SIDM case (s ≈ 0.75). The speed distribution f(v) of dark matter particles at the location of the Sun in the inelastic SIDM model shows a significant departure from the CDM model, with f(v) falling more steeply at high speeds. In addition, the velocity kicks imparted during inelastic collisions produce unbound high-speed particles with velocities up to 500 km s−1 throughout the halo. This implies that inelastic SIDM can potentially leave distinct signatures in direct detection experiments, relative to elastic SIDM and CDM.

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A numerical study on the distribution of the debris of the Milky Way satellites

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318005306 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 105-108

Author(s):

Matteo Mazzarini ◽

Andreas Just

Keyword(s):

Dark Matter ◽

Gas Dynamics ◽

Milky Way ◽

Galactic Disk ◽

Numerical Study ◽

Major Axis ◽

Space Distribution ◽

Axis Ratio ◽

Phase Space Distribution ◽

The Impact

AbstractWe perform six N-body simulations reproducing the interaction between the Milky Way and its satellite galaxies, in order to address the deposit of satellite debris in the Galactic environment. We find that most of the baryons survive inside their host satellites and that most of the baryonic debris ends up in the inner regions of the Milky Way, in contrast to the more uniform distribution of dark matter debris. We also look at the debris Inertia tensor in the inner regions of the Milky Way and find a lower minor-to-major axis ratio for baryons than dark matter. We plan to explore the phase-space distribution of the debris ending in the Galactic disk and bulge. We also plan further simulations including gas dynamics to study the impact of gas on the process.

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Predictably missing satellites: subhalo abundances in Milky Way-like haloes

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1098 ◽

2019 ◽

Vol 486 (4) ◽

pp. 4545-4568 ◽

Cited By ~ 5

Author(s):

Catherine E Fielder ◽

Yao-Yuan Mao ◽

Jeffrey A Newman ◽

Andrew R Zentner ◽

Timothy C Licquia

Keyword(s):

Dark Matter ◽

Confidence Level ◽

Mass Concentration ◽

Cold Dark Matter ◽

Milky Way ◽

Scale Factor ◽

Magellanic Clouds ◽

Small Scales ◽

Major Merger ◽

The Impact

ABSTRACT On small scales there have been a number of claims of discrepancies between the standard cold dark matter (CDM) model and observations. The ‘missing satellites problem’ infamously describes the overabundance of subhaloes from CDM simulations compared to the number of satellites observed in the Milky Way. A variety of solutions to this discrepancy have been proposed; however, the impact of the specific properties of the Milky Way halo relative to the typical halo of its mass has yet to be explored. Motivated by recent studies that identified ways in which the Milky Way is atypical, we investigate how the properties of dark matter haloes with mass comparable to our Galaxy’s – including concentration, spin, shape, and scale factor of the last major merger – correlate with the subhalo abundance. Using zoom-in simulations of Milky Way-like haloes, we build two models of subhalo abundance as functions of host halo properties. From these models we conclude that the Milky Way most likely has fewer subhaloes than the average halo of the same mass. We expect up to 30 per cent fewer subhaloes with low maximum rotation velocities ($V_{\rm max}^{\rm sat} \sim 10$ km s−1) at the 68 per cent confidence level and up to 52 per cent fewer than average subhaloes with high rotation velocities ($V_{\rm max}^{\rm sat} \gtrsim 30$ km s−1, comparable to the Magellanic Clouds) than would be expected for a typical halo of the Milky Way’s mass. Concentration is the most informative single parameter for predicting subhalo abundance. Our results imply that models tuned to explain the missing satellites problem assuming typical subhalo abundances for our Galaxy may be overcorrecting.

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SEARCHING FOR AXIONS AND OTHER EXOTICS WITH DARK MATTER DETECTORS

International Journal of Modern Physics A ◽

10.1142/s0217751x10048858 ◽

2010 ◽

Vol 25 (02n03) ◽

pp. 564-572

Author(s):

MAXIM POSPELOV

Keyword(s):

Dark Matter ◽

Standard Model ◽

Cold Dark Matter ◽

Direct Detection ◽

Annual Modulation ◽

The Standard Model ◽

Detection Capabilities ◽

The Impact ◽

Particle Decays ◽

O 10

I consider models of light super-weakly interacting cold dark matter, with [Formula: see text] mass, focusing on bosonic candidates such as pseudoscalars and vectors. I analyze the cosmological abundance, the γ-background created by particle decays, the impact on stellar processes due to cooling, and the direct detection capabilities in order to identify classes of models that pass all the constraints. In certain models, variants of photoelectric (or axioelectric) absorption of dark matter in direct-detection experiments can provide a sensitivity to the superweak couplings to the Standard Model which is superior to all existing indirect constraints. In all models studied, the annual modulation of the direct-detection signal is at the currently unobservable level of O(10-5).

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Implications of hydrodynamical simulations for the interpretation of direct dark matter searches

International Journal of Modern Physics A ◽

10.1142/s0217751x17300162 ◽

2017 ◽

Vol 32 (21) ◽

pp. 1730016 ◽

Cited By ~ 22

Author(s):

Nassim Bozorgnia ◽

Gianfranco Bertone

Keyword(s):

Dark Matter ◽

Velocity Distribution ◽

Milky Way ◽

Direct Detection ◽

Solar Neighborhood ◽

Reliable Estimate ◽

The Status ◽

Hydrodynamical Simulations ◽

The Impact ◽

Direct Dark Matter

In recent years, realistic hydrodynamical simulations of galaxies like the Milky Way have become available, enabling a reliable estimate of the dark matter density and velocity distribution in the Solar neighborhood. We review here the status of hydrodynamical simulations and their implications for the interpretation of direct dark matter searches. We focus in particular on: the criteria to identify Milky Way-like galaxies; the impact of baryonic physics on the dark matter velocity distribution; the possible presence of substructures like clumps, streams, or dark disks; and on the implications for the direct detection of dark matter with standard and nonstandard interactions.

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To Observe, or Not to Observe, Quantum-Coherent Dark Matter in the Milky Way, That is a Question

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.697140 ◽

2021 ◽

Vol 8 ◽

Author(s):

Tanja Rindler-Daller

Keyword(s):

Dark Matter ◽

Scalar Field ◽

Structure Formation ◽

Cold Dark Matter ◽

Milky Way ◽

Small Scale ◽

Quantum Mechanical ◽

Bose Einstein ◽

The Impact ◽

Observational Signature

In recent years, Bose-Einstein-condensed dark matter (BEC-DM) has become a popular alternative to standard, collisionless cold dark matter (CDM). This BEC-DM -also called scalar field dark matter (SFDM)- can suppress structure formation and thereby resolve the small-scale crisis of CDM for a range of boson masses. However, these same boson masses also entail implications for BEC-DM substructure within galaxies, especially within our own Milky Way. Observational signature effects of BEC-DM substructure depend upon its unique quantum-mechanical features and have the potential to reveal its presence. Ongoing efforts to determine the dark matter substructure in our Milky Way will continue and expand considerably over the next years. In this contribution, we will discuss some of the existing constraints and potentially new ones with respect to the impact of BEC-DM onto baryonic tracers. Studying dark matter substructure in our Milky Way will soon resolve the question, whether dark matter behaves classical or quantum on scales of ≲ 1 kpc.

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The spatial distribution of Milky Way satellites, gaps in streams and the nature of dark matter

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2452 ◽

2021 ◽

Author(s):

Mark R Lovell ◽

Marius Cautun ◽

Carlos S Frenk ◽

Wojciech A Hellwing ◽

Oliver Newton

Keyword(s):

Dark Matter ◽

Spatial Distribution ◽

High Resolution ◽

Radial Distribution ◽

Cold Dark Matter ◽

Milky Way ◽

Self Consistent ◽

Low Mass ◽

Hydrodynamical Simulations ◽

The Impact

Abstract The spatial distribution of Milky Way (MW) subhaloes provides an important set of observables for testing cosmological models. These include the radial distribution of luminous satellites, planar configurations, and the abundance of dark subhaloes whose existence or absence is key to distinguishing amongst dark matter models. We use the coco N-body simulations of cold dark matter (CDM) and 3.3 keV thermal relic warm dark matter (WDM) to predict the satellite spatial distribution in the limit that the impact of baryonic physics is minimal. We demonstrate that the radial distributions of CDM and 3.3 keV-WDM luminous satellites are identical if the minimum pre-infall halo mass to form a galaxy is >108.5 ${\, \rm M_\odot }$. The distribution of dark subhaloes is significantly more concentrated in WDM due to the absence of low mass, recently accreted substructures that typically inhabit the outer parts of a MW halo in CDM. We show that subhaloes of mass [107, 108] ${\, \rm M_\odot }$ and within 30 kpc of the centre are the stripped remnants of larger haloes in both models. Therefore their abundance in WDM is 3 × higher than one would anticipate from the overall WDM subhalo population. We estimate that differences between CDM and WDM concentration–mass relations can be probed for subhalo–stream impact parameters <2 kpc. Finally, we find that the impact of WDM on planes of satellites is likely negligible. Comprehensive comparisons with observations will require further work with high resolution, self-consistent hydrodynamical simulations.

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Out of sight, out of mind? The impact of correlated clustering in substructure lensing

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab448 ◽

2021 ◽

Author(s):

Alexandres Lazar ◽

James S Bullock ◽

Michael Boylan-Kolchin ◽

Robert Feldmann ◽

Onur Çatmabacak ◽

...

Keyword(s):

Dark Matter ◽

Principal Axis ◽

Major Axis ◽

Line Of Sight ◽

Gravitational Lenses ◽

Local Clustering ◽

Analytic Expression ◽

Halo Masses ◽

The Impact

Abstract A promising route for revealing the existence of dark matter structures on mass scales smaller than the faintest galaxies is through their effect on strong gravitational lenses. We examine the role of local, lens-proximate clustering in boosting the lensing probability relative to contributions from substructure and unclustered line-of-sight (LOS) haloes. Using two cosmological simulations that can resolve halo masses of Mhalo ≃ 109 M⊙ (in a simulation box of length Lbox ∼ 100 Mpc) and 107 M⊙ (Lbox ∼ 20 Mpc), we demonstrate that clustering in the vicinity of the lens host produces a clear enhancement relative to an assumption of unclustered haloes that persists to >20 Rvir. This enhancement exceeds estimates that use a two-halo term to account for clustering, particularly within 2 − 5 Rvir. We provide an analytic expression for this excess, clustered contribution. We find that local clustering boosts the expected count of 109 M⊙ perturbing haloes by ${\sim }35{{\ \rm per\ cent}}$ compared to substructure alone, a result that will significantly enhance expected signals for low-redshift (zl ≃ 0.2) lenses, where substructure contributes substantially compared to LOS haloes. We also find that the orientation of the lens with respect to the line of sight (e.g. whether the line of sight passes through the major axis of the lens) can also have a significant effect on the lensing signal, boosting counts by an additional $\sim 50{{\ \rm per\ cent}}$ compared to a random orientations. This could be important if discovered lenses are biased to be oriented along their principal axis.

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Probing non-spherical dark halos in the Galactic dwarf satellites

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313006789 ◽

2013 ◽

Vol 9 (S298) ◽

pp. 411-411

Author(s):

Kohei Hayashi ◽

Masashi Chiba

Keyword(s):

Dark Matter ◽

Cold Dark Matter ◽

Milky Way ◽

Velocity Dispersion ◽

Line Of Sight ◽

Spherical Structure ◽

Spherical Models ◽

Galactic Satellites ◽

Best Fitting

AbstractWe construct axisymmetric mass models for dwarf spheroidal (dSph) galaxies in the Milky Way to obtain realistic limits on the non-spherical structure of their dark halos. This is motivated by the fact that the observed luminous parts of the dSphs are actually non-spherical and cold dark matter models predict non-spherical virialized dark halos on sub-galactic scales. Applying these models to line-of-sight velocity dispersion profiles along three position angles in six Galactic satellites, we find that the best fitting cases for most of the dSphs yield not spherical but oblate and flattened dark halos. We also find that the mass of the dSphs enclosed within inner 300 pc varies depending on their total luminosities, contrary to the conclusion of previous spherical models. This suggests the importance of considering non-spherical shapes of dark halos in dSph mass models.

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