scholarly journals Continuum-mediated self-interacting dark matter

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Ian Chaffey ◽  
Sylvain Fichet ◽  
Philip Tanedo
Keyword(s):  
Dark Matter ◽  
Yukawa Potential ◽  
Spatial Separation ◽  
Small Scale ◽  
Interaction Cross Section ◽  
De Sitter ◽  
Strongly Coupled ◽  
Integer Power ◽  
Low Mass ◽  
Sommerfeld Enhancement

Abstract Dark matter may self-interact through a continuum of low-mass states. This happens if dark matter couples to a strongly-coupled nearly-conformal hidden sector. This type of theory is holographically described by brane-localized dark matter interacting with bulk fields in a slice of 5D anti-de Sitter space. The long-range potential in this scenario depends on a non-integer power of the spatial separation, in contrast to the Yukawa potential generated by the exchange of a single 4D mediator. The resulting self-interaction cross section scales like a non-integer power of velocity. We identify the Born, classical and resonant regimes and investigate them using state-of-the-art numerical methods. We demonstrate the viability of our continuum-mediated framework to address the astrophysical small-scale structure anomalies. Investigating the continuum-mediated Sommerfeld enhancement, we demonstrate that a pattern of resonances can occur depending on the non-integer power. We conclude that continuum mediators introduce novel power-law scalings which open new possibilities for dark matter self-interaction phenomenology.

scholarly journals Simulating the complexity of the dark matter sheet I: numerical algorithms

2020 ◽  
Vol 495 (4) ◽  
pp. 4943-4964
Author(s):  
Jens Stücker ◽  
Oliver Hahn ◽  
Raul E Angulo ◽  
Simon D M White
Keyword(s):  
Dark Matter ◽  
Numerical Algorithms ◽  
Linear Structure ◽  
Small Scale ◽  
Deviation Equation ◽  
Unknown Amplitude ◽  
Low Mass ◽  
Force Resolution ◽  
Force Calculation ◽  
Matter Phase

ABSTRACT At early times, dark matter has a thermal velocity dispersion of unknown amplitude which, for warm dark matter (WDM) models, can influence the formation of non-linear structure on observable scales. We propose a new scheme to simulate cosmologies with a small-scale suppression of perturbations that combines two previous methods in a way that avoids the numerical artefacts which have so far prevented either from producing fully reliable results. At low densities and throughout most of the cosmological volume, we represent the dark matter phase sheet directly using high-accuracy interpolation, thereby avoiding the artificial fragmentation which afflicts particle-based methods in this regime. Such phase-sheet methods are, however, unable to follow the rapidly increasing complexity of the denser regions of dark matter haloes, so for these we switch to an N-body scheme which uses the geodesic deviation equation to track phase-sheet properties local to each particle. In addition, we present a novel high-resolution force calculation scheme based on an oct-tree of cubic force resolution elements which is well suited to approximate the force field of our combined sheet+particle distribution. Our hybrid simulation scheme enables the first reliable simulations of the internal structure of low-mass haloes in a WDM cosmology.

scholarly journals Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

2004 ◽  
Vol 220 ◽  
pp. 91-98 ◽  
Author(s):  
J. E. Taylor ◽  
J. Silk ◽  
A. Babul
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Small Scale ◽  
Analytic Model ◽  
Model Predictions ◽  
Low Mass

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

scholarly journals Double dark matter vision: twice the number of compact-source lenses with narrow-line lensing and the WFC3 grism

2019 ◽  
Vol 492 (4) ◽  
pp. 5314-5335 ◽  
Author(s):  
A M Nierenberg ◽  
D Gilman ◽  
T Treu ◽  
G Brammer ◽  
S Birrer ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Line Emission ◽  
Companion Paper ◽  
Small Scale ◽  
Gravitational Lenses ◽  
Narrow Line ◽  
Entire Sample ◽  
Compact Source ◽  
Low Mass

ABSTRACT The magnifications of compact-source lenses are extremely sensitive to the presence of low-mass dark matter haloes along the entire sightline from the source to the observer. Traditionally, the study of dark matter structure in compact-source strong gravitational lenses has been limited to radio-loud systems, as the radio emission is extended and thus unaffected by microlensing which can mimic the signal of dark matter structure. An alternate approach is to measure quasar nuclear-narrow-line emission, which is free from microlensing and present in virtually all quasar lenses. In this paper, we double the number of systems which can be used for gravitational lensing analyses by presenting measurements of narrow-line emission from a sample of eight quadruply imaged quasar lens systems, WGD J0405−3308, HS 0810+2554, RX J0911+0551, SDSS J1330+1810, PS J1606−2333, WFI 2026−4536, WFI 2033−4723, and WGD J2038−4008. We describe our updated grism spectral modelling pipeline, which we use to measure narrow-line fluxes with uncertainties of 2–10 per cent, presented here. We fit the lensed image positions with smooth mass models and demonstrate that these models fail to produce the observed distribution of image fluxes over the entire sample of lenses. Furthermore, typical deviations are larger than those expected from macromodel uncertainties. This discrepancy indicates the presence of perturbations caused by small-scale dark matter structure. The interpretation of this result in terms of dark matter models is presented in a companion paper.

scholarly journals Seeking Observable Imprints of Small-Scale Structure on the Properties of Dark Matter Haloes

2013 ◽  
Vol 30 ◽  
Author(s):  
C. Power
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Spatial Clustering ◽  
Scale Structure ◽  
Small Scale ◽  
Halo Formation ◽  
Potential Wells ◽  
Massive Galaxies ◽  
Small Scale Structure ◽  
Low Mass

AbstractThe characteristic prediction of the Cold Dark Matter (CDM) model of cosmological structure formation is that the Universe should contain a wealth of small-scale structure—low-mass dark matter haloes and subhaloes. However, galaxy formation is inefficient in their shallow potential wells and so we expect these low-mass haloes and subhaloes to be dark. Can we tell the difference between a Universe in which these low-mass haloes are present but dark and one in which they never formed, thereby providing a robust test of the CDM model? We address this question using cosmological N-body simulations to examine how properties of low-mass haloes that are potentially accessible to observation, such as their spatial clustering, rate of accretions and mergers onto massive galaxies, and the angular momentum content of massive galaxies, differ between a fiducial ΛCDM model and dark matter models in which low-mass halo formation is suppressed. Adopting an effective cut-off mass scale Mcut below which small-scale power is suppressed in the initial conditions, we study dark matter models in which Mcut varies between 5×109h−1M⊙ and 1011h−1M⊙, equivalent to the host haloes of dwarf and low-mass galaxies. Our results show that both the clustering strength of low-mass haloes around galaxy-mass primaries and the rate at which they merge with these primaries are sensitive to the assumed value of Mcut; in contrast, suppressing low-mass halo formation has little influence on the angular momentum content of galaxy-mass haloes—it is the quiescence or violence of a halo's assembly history that has a more marked effect. However, we expect that measuring the effect on spatial clustering or the merger rate is likely to be observationally difficult for realistic values of Mcut, and so isolating the effect of this small-scale structure would appear to be remarkably difficult to detect, at least in the present day Universe.

scholarly journals The Role of Small Scale Experiments in the Direct Detection of Dark Matter

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 81
Author(s):  
Susana Cebrián
Keyword(s):  
Dark Matter ◽  
New Technologies ◽  
Direct Detection ◽  
Detection Methods ◽  
Small Scale ◽  
Detection Systems ◽  
Relevant Role ◽  
Low Mass ◽  
Complex Detection

In the direct detection of the galactic dark matter, experiments using cryogenic solid-state detectors or noble liquids play for years a very relevant role, with increasing target mass and more and more complex detection systems. But smaller projects, based on very sensitive, advanced detectors following new technologies, could help in the exploration of the different proposed dark matter scenarios too. There are experiments focused on the observation of distinctive signatures of dark matter, like an annual modulation of the interaction rates or the directionality of the signal; other ones are intended to specifically investigate low mass dark matter candidates or particular interactions. For this kind of dark matter experiments at small scale, the physics case will be discussed and selected projects will be described, summarizing the basics of their detection methods and presenting their present status, recent results and prospects.

scholarly journals Constraining the non-gravitational scattering of baryons and dark matter with early cosmic structure formation

2019 ◽  
Vol 487 (4) ◽  
pp. 4711-4720 ◽  
Author(s):  
Boyuan Liu ◽  
Anna T P Schauer ◽  
Volker Bromm
Keyword(s):  
Dark Matter ◽  
Structure Formation ◽  
Particle Physics ◽  
Small Scale ◽  
Interaction Cross Section ◽  
Number Density ◽  
Absorption Signal ◽  
Measured Absorption ◽  
Sigma 1 ◽  
Dark Matter Scattering

ABSTRACT We derive new constraints on the non-gravitational baryon-dark matter scattering (BDMS) by evaluating the mass thresholds of dark matter (DM) haloes in which primordial gas can cool efficiently to form Population III (Pop III) stars, based on the timing of the observed 21 cm absorption signal. We focus on the BDMS model with interaction cross-section $\sigma =\sigma _{1}[v/(1\ \mathrm{km\, s^{-1}})]^{-4}$, where v is the relative velocity of the encounter. Our results rule out the region in parameter space with $\sigma _{1}\gtrsim 10^{-19}\, \mathrm{cm^{2}}$ and DM particle mass mχc2 ≲ 3 × 10−2 GeV, where the cosmic number density of Pop III hosts at redshift z ∼ 20 is at least three orders of magnitude smaller than in the standard Lambda cold DM (ΛCDM) case. In these BDMS models, the formation of Pop III stars is significantly suppressed for z ≳ 20, inconsistent with the timing of the observed global 21 cm absorption signal. For the fiducial BDMS model with mχc2 = 0.3 GeV and $\sigma _{1}=8\times 10^{-20}\, \mathrm{cm^{2}}$, capable of accommodating the measured absorption depth, the number density of Pop III hosts is reduced by a factor of 3−10 at z ∼ 15−20, when the 21 cm signal is imprinted, compared with the ΛCDM model. The confluence of future detailed cosmological simulations with improved 21 cm observations promises to probe the particle-physics nature of DM at the small-scale frontier of early structure formation.

scholarly journals QPOs in compact binaries from small scale eruptions in an inner magnetized disk

2020 ◽  
Author(s):  
Nicolas Scepi ◽  
Mitchell C Begelman ◽  
Jason Dexter
Keyword(s):  
Rapid Heating ◽  
Small Scale ◽  
Type B ◽  
Periodic Oscillations ◽  
X Ray ◽  
Compact Binaries ◽  
Heating And Cooling ◽  
Low Mass ◽  
X Ray Binaries ◽  
Standard Disk

Abstract Dwarf novæ (DNe) and low mass X-ray binaries (LMXBs) are compact binaries showing variability on time scales from years to less than seconds. Here, we focus on explaining part of the rapid fluctuations in DNe, following the framework of recent studies on the monthly eruptions of DNe that use a hybrid disk composed of an outer standard disk and an inner magnetized disk. We show that the ionization instability, that is responsible for the monthly eruptions of DNe, is also able to operate in the inner magnetized disk. Given the low density and the fast accretion time scale of the inner magnetized disk, the ionization instability generates small, rapid heating and cooling fronts propagating back and forth in the inner disk. This leads to quasi-periodic oscillations (QPOs) with a period of the order of 1000 s. A strong prediction of our model is that these QPOs can only develop in quiescence or at the beginning/end of an outburst. We propose that these rapid fluctuations might explain a subclass of already observed QPOs in DNe as well as a, still to observe, subclass of QPOs in LMXBs. We also extrapolate to the possibility that the radiation pressure instability might be related to Type B QPOs in LMXBs.

scholarly journals On N-body simulations of globular cluster streams

2021 ◽  
Vol 504 (1) ◽  
pp. 648-653
Author(s):  
Nilanjan Banik ◽  
Jo Bovy
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Analytical Models ◽  
Numerical Density ◽  
Stellar Streams ◽  
Small Scales ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Stream Density ◽  
Tidal Streams

ABSTRACT Stellar tidal streams are sensitive tracers of the properties of the gravitational potential in which they orbit and detailed observations of their density structure can be used to place stringent constraints on fluctuations in the potential caused by, e.g. the expected populations of dark matter subhaloes in the standard cold dark matter (CDM) paradigm. Simulations of the evolution of stellar streams in live N-body haloes without low-mass dark matter subhaloes, however, indicate that streams exhibit significant perturbations on small scales even in the absence of substructure. Here, we demonstrate, using high-resolution N-body simulations combined with sophisticated semi-analytical and simple analytical models, that the mass resolutions of 104–$10^5\, \rm {M}_{\odot }$ commonly used to perform such simulations cause spurious stream density variations with a similar magnitude on large scales as those expected from a CDM-like subhalo population and an order of magnitude larger on small, yet observable, scales. We estimate that mass resolutions of ${\approx}100\, \rm {M}_{\odot }$ (${\approx}1\, \rm {M}_{\odot }$) are necessary for spurious, numerical density variations to be well below the CDM subhalo expectation on large (small) scales. That streams are sensitive to a simulation’s particle mass down to such small masses indicates that streams are sensitive to dark matter clustering down to these low masses if a significant fraction of the dark matter is clustered or concentrated in this way, for example, in MACHO models with masses of 10–$100\, \rm {M}_{\odot }$.

scholarly journals Improving sensitivity to low-mass dark matter in LUX using a novel electrode background mitigation technique

2021 ◽  
Vol 104 (1) ◽  
Author(s):  
D. S. Akerib ◽  
S. Alsum ◽  
H. M. Araújo ◽  
X. Bai ◽  
J. Balajthy ◽  
...  
Keyword(s):  
Dark Matter ◽  
Low Mass ◽  
Mitigation Technique

scholarly journals Understanding the large inferred Einstein radii of observed low-mass galaxy clusters

2020 ◽  
Vol 494 (4) ◽  
pp. 4706-4712 ◽  
Author(s):  
Andrew Robertson ◽  
Richard Massey ◽  
Vincent Eke
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
Baryonic Matter ◽  
Analysis Method ◽  
Critical Curves ◽  
Hydrodynamical Simulation ◽  
Low Mass ◽  
Main Effects

ABSTRACT We assess a claim that observed galaxy clusters with mass ${\sim}10^{14} \mathrm{\, M_\odot }$ are more centrally concentrated than predicted in lambda cold dark matter (ΛCDM). We generate mock strong gravitational lensing observations, taking the lenses from a cosmological hydrodynamical simulation, and analyse them in the same way as the real Universe. The observed and simulated lensing arcs are consistent with one another, with three main effects responsible for the previously claimed inconsistency. First, galaxy clusters containing baryonic matter have higher central densities than their counterparts simulated with only dark matter. Secondly, a sample of clusters selected because of the presence of pronounced gravitational lensing arcs preferentially finds centrally concentrated clusters with large Einstein radii. Thirdly, lensed arcs are usually straighter than critical curves, and the chosen image analysis method (fitting circles through the arcs) overestimates the Einstein radii. After accounting for these three effects, ΛCDM predicts that galaxy clusters should produce giant lensing arcs that match those in the observed Universe.

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