scholarly journals CONSTANT SURFACE GRAVITY AND DENSITY PROFILE OF DARK MATTER

2011 ◽  
Vol 26 (06) ◽  
pp. 1057-1072 ◽  
Author(s):  
H. J. DE VEGA ◽  
N. G. SANCHEZ
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Particle Physics ◽  
Black Hole Entropy ◽  
Density Fluctuations ◽  
Surface Gravity ◽  
Density Profiles ◽  
Physics Model ◽  
Physical Consequences ◽  
Remarkable Agreement

Cumulative observational evidence confirms that the surface gravity of dark matter (DM) halos μ0 D = r0ρ0, where r0 and ρ0 are the halo core radius and central density, respectively, is nearly constant and independent of galaxy luminosity for a high number of galactic systems (spirals, dwarf irregular and spheroidals, elliptics) spanning over 14 magnitudes in luminosity and of different Hubble types. Remarkably, its numerical value, μ0D ≃140M⊙/ pc 2 = (18.6 MeV )3, is approximately the same (up to a factor of 2) in all these systems. First, we present the physical consequences of the independence of μ0D from r0: the energy scales as the volume [Formula: see text], while the mass and the entropy scale as the surface [Formula: see text] and the surface times log r0, respectively. Namely, the entropy scales similarly to the black hole entropy but with a much smaller coefficient. Second, we compute the surface gravity and the density profile for small scales from first principles and the evolution of primordial density fluctuations from the end of inflation till today using the linearized Boltzmann–Vlasov equation. The density profile ρ lin (r) obtained in this way decreases as r-1-ns/2 for intermediate scales, where ns≃0.964 is the primordial spectral index. This scaling is in remarkable agreement with the empirical behavior found observationally and in N-body simulations: r-1.6±0.4. The observed value of μ0D indicates that the DM particle mass m is on the keV scale. The theoretically derived density profiles ρ lin (r) turn to be cored for m on the keV scale and they are cusped for m on the GeV scale or beyond. We consider both fermions and bosons as DM particles decoupling either ultrarelativistically or nonrelativistically. Our results do not use any particle physics model and vary slightly with the statistics of the DM particle.

scholarly journals Xenon-1T excess as a possible signal of a sub-GeV hidden sector dark matter

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Amin Aboubrahim ◽  
Michael Klasen ◽  
Pran Nath
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Small Mass ◽  
Big Bang ◽  
Mass Splitting ◽  
Recoil Energy ◽  
Dirac Fermions ◽  
Dark Sector ◽  
Dark Photon ◽  
Physics Model

Abstract We present a particle physics model to explain the observed enhancement in the Xenon-1T data at an electron recoil energy of 2.5 keV. The model is based on a U(1) extension of the Standard Model where the dark sector consists of two essentially mass degenerate Dirac fermions in the sub-GeV region with a small mass splitting interacting with a dark photon. The dark photon is unstable and decays before the big bang nucleosynthesis, which leads to the dark matter constituted of two essentially mass degenerate Dirac fermions. The Xenon-1T excess is computed via the inelastic exothermic scattering of the heavier dark fermion from a bound electron in xenon to the lighter dark fermion producing the observed excess events in the recoil electron energy. The model can be tested with further data from Xenon-1T and in future experiments such as SuperCDMS.

scholarly journals Wave Dark Matter

2021 ◽  
Vol 59 (1) ◽  
pp. 247-289
Author(s):  
Lam Hui
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Particle Physics ◽  
Density Fluctuations ◽  
Dark Matter Candidate ◽  
Order Unity ◽  
Wave Interference ◽  
Wave Nature ◽  
Tidal Streams ◽  
Wave Dark Matter

We review the physics and phenomenology of wave dark matter: a bosonic dark matter candidate lighter than about 30 eV. Such particles have a de Broglie wavelength exceeding the average interparticle separation in a galaxy like the Milky Way and are, thus, well described as a set of classical waves. We outline the particle physics motivations for such particles, including the quantum chromodynamics axion as well as ultralight axion-like particles such as fuzzy dark matter. The wave nature of the dark matter implies a rich phenomenology: ▪  Wave interference gives rise to order unity density fluctuations on de Broglie scale in halos. One manifestation is vortices where the density vanishes and around which the velocity circulates. There is one vortex ring per de Broglie volume on average. ▪  For sufficiently low masses, soliton condensation occurs at centers of halos. The soliton oscillates and undergoes random walks, which is another manifestation of wave interference. The halo and subhalo abundance is expected to be suppressed at small masses, but the precise prediction from numerical wave simulations remains to be determined. ▪  For ultralight ∼10−22 eV dark matter, the wave interference substructures can be probed by tidal streams or gravitational lensing. The signal can be distinguished from that due to subhalos by the dependence on stream orbital radius or image separation. ▪  Axion detection experiments are sensitive to interference substructures for wave dark matter that is moderately light. The stochastic nature of the waves affects the interpretation of experimental constraints and motivates the measurement of correlation functions. Current constraints and open questions, covering detection experiments and cosmological, galactic, and black hole observations, are discussed.

scholarly journals Answers from the Void: VIDE and its Applications

2014 ◽  
Vol 11 (S308) ◽  
pp. 524-529
Author(s):  
P. M. Sutter ◽  
N. Hamaus ◽  
A. Pisani ◽  
G. Lavaux ◽  
B. D. Wandelt
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Statistical Information ◽  
Distribution Model ◽  
Density Profiles ◽  
Redshift Surveys ◽  
Primordial Magnetic Fields ◽  
Galaxy Redshift ◽  
Galaxy Populations ◽  
Halo Occupation Distribution

AbstractWe discuss various applications of vide, the Void IDentification and Examination toolkit, an open-source Python/C++ code for finding cosmic voids in galaxy redshift surveys and $N$-body simulations. Based on a substantially enhanced version of ZOBOV, vide not only finds voids, but also summarizes their properties, extracts statistical information, and provides a Python-based platform for more detailed analysis, such as manipulating void catalogs and particle members, filtering, plotting, computing clustering statistics, stacking, comparing catalogs, and fitting density profiles. vide also provides significant additional functionality for pre-processing inputs: for example, vide can work with volume- or magnitude-limited galaxy samples with arbitrary survey geometries, or dark matter particles or halo catalogs in a variety of common formats. It can also randomly subsample inputs and includes a Halo Occupation Distribution model for constructing mock galaxy populations. vide has been used for a wide variety of applications, from discovering a universal density profile to estimating primordial magnetic fields, and is publicly available at http://bitbucket.org/cosmicvoids/vide\_public and http://www.cosmicvoids.net.

scholarly journals Probing the nature of dark matter with accreted globular cluster streams

2020 ◽  
Vol 501 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Khyati Malhan ◽  
Monica Valluri ◽  
Katherine Freese
Keyword(s):  
Dark Matter ◽  
Globular Cluster ◽  
Particle Physics ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Density Profiles ◽  
Parallel Structures ◽  
Stellar Streams ◽  
Future Data ◽  
Low Mass

ABSTRACT The steepness of the central density profiles of dark matter (DM) in low-mass galaxy haloes (e.g. dwarf galaxies) is a powerful probe of the nature of DM. We propose a novel scheme to probe the inner profiles of galaxy subhaloes using stellar streams. We show that the present-day morphological and dynamical properties of accreted globular cluster (GC) streams – those produced from tidal stripping of GCs that initially evolved within satellite galaxies and later merged with the Milky Way (MW) – are sensitive to the central DM density profile and mass of their parent satellites. GCs that accrete within cuspy cold dark matter (CDM) subhaloes produce streams that are physically wider and dynamically hotter than streams that accrete inside cored subhaloes. A first comparison of MW streams ‘GD-1’ and ‘Jhelum’ (likely of accreted GC origin) with our simulations indicates a preference for cored subhaloes. If these results hold up in future data, the implication is that either the DM cusps were erased by baryonic feedback, or their subhaloes naturally possessed cored density profiles implying particle physics models beyond CDM. Moreover, accreted GC streams are highly structured and exhibit complex morphological features (e.g. parallel structures and ‘spurs’). This implies that the accretion scenario can naturally explain the recently observed peculiarities in some of the MW streams. We also propose a novel mechanism for forming ‘gaps’ in stellar streams when the remnant of the parent subhalo (which hosted the GC) later passes through the GC stream. This encounter can last a longer time (and have more of an impact) than the random encounters with DM subhaloes previously considered, because the GC stream and its parent subhalo are on similar orbits with small relative velocities. Current and future surveys of the MW halo will uncover numerous faint stellar streams and provide the data needed to substantiate our preliminary tests with this new probe of DM.

scholarly journals DARK MATTER ANNIHILATION EXPLANATION FOR e± EXCESSES IN COSMIC RAY

2009 ◽  
Vol 24 (27) ◽  
pp. 2139-2160 ◽  
Author(s):  
XIAO-GANG HE
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Cosmic Ray ◽  
Proton Spectrum ◽  
Annihilation Rate ◽  
Dark Matter Annihilation ◽  
Data Set ◽  
Boost Factor ◽  
Physics Model ◽  
Correct Data

Recently data from PAMELA, ATIC, FERMI-LAT and HESS show that there are e± excesses in the cosmic ray energy spectrum. PAMELA shown excesses only in e+, but not in anti-proton spectrum. ATIC, FERMI-LAT and HESS shown excesses in e++e- spectrum, but the detailed shapes are different which requires future experimental observations to pin down the correct data set. Nevertheless a lot of efforts have been made to explain the observed e± excesses, and also why PAMELA only has excesses in e+ but not in anti-proton. In this brief review we discuss one of the most popular mechanisms to explain the data — the dark matter annihilation. It has long been known that about 23% of our universe is made of relic dark matter. If the relic dark matter was thermally produced, the annihilation rate is constrained resulting in the need of a large boost factor to explain the data. We will discuss in detail how a large boost factor can be obtained by the Sommerfeld and Breit–Wigner enhancement mechanisms. Some implications for particle physics model buildings will also be discussed.

scholarly journals The splashback boundary of haloes in hydrodynamic simulations

2021 ◽  
Author(s):  
Stephanie O’Neil ◽  
David J Barnes ◽  
Mark Vogelsberger ◽  
Benedikt Diemer
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Accretion Rate ◽  
Radial Density ◽  
Density Profiles ◽  
Hydrodynamic Simulations ◽  
Mass Accretion Rate ◽  
Significant Difference ◽  
Satellite Galaxies

Abstract The splashback radius, Rsp, is a physically motivated halo boundary that separates infalling and collapsed matter of haloes. We study Rsp in the hydrodynamic and dark matter only IllustrisTNG simulations. The most commonly adopted signature of Rsp is the radius at which the radial density profiles are steepest. Therefore, we explicitly optimise our density profile fit to the profile slope and find that this leads to a $\sim 5\%$ larger radius compared to other optimisations. We calculate Rsp for haloes with masses between 1013 − 15M⊙ as a function of halo mass, accretion rate and redshift. Rsp decreases with mass and with redshift for haloes of similar M200m in agreement with previous work. We also find that Rsp/R200m decreases with halo accretion rate. We apply our analysis to dark matter, gas and satellite galaxies associated with haloes to investigate the observational potential of Rsp. The radius of steepest slope in gas profiles is consistently smaller than the value calculated from dark matter profiles. The steepest slope in galaxy profiles, which are often used in observations, tends to agree with dark matter profiles but is lower for less massive haloes. We compare Rsp in hydrodynamic and N-body dark matter only simulations and do not find a significant difference caused by the addition of baryonic physics. Thus, results from dark matter only simulations should be applicable to realistic haloes.

scholarly journals CLASH-VLT: a full dynamical reconstruction of the mass profile of Abell S1063 from 1 kpc out to the virial radius

2020 ◽  
Vol 637 ◽  
pp. A34 ◽  
Author(s):  
B. Sartoris ◽  
A. Biviano ◽  
P. Rosati ◽  
A. Mercurio ◽  
C. Grillo ◽  
...  
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Dynamical Analysis ◽  
Cluster Galaxy ◽  
Data Set ◽  
Density Profiles ◽  
Dispersion Profile ◽  
Mass Profile

Context. The shape of the mass density profiles of cosmological halos informs us of the nature of dark matter (DM) and DM-baryons interactions. Previous estimates of the inner slope of the mass density profiles of clusters of galaxies are in opposition to predictions derived from numerical simulations of cold dark matter (CDM). Aims. We determine the inner slope of the DM density profile of a massive cluster of galaxies, Abell S1063 (RXC J2248.7−4431) at z = 0.35, with a dynamical analysis based on an extensive spectroscopic campaign carried out with the VIMOS and MUSE spectrographs at the ESO VLT. This new data set provides an unprecedented sample of 1234 spectroscopic members, 104 of which are located in the cluster core (R ≲ 200 kpc), extracted from the MUSE integral field spectroscopy. The latter also allows the stellar velocity dispersion profile of the brightest cluster galaxy (BCG) to be measured out to 40 kpc. Methods. We used an upgraded version of the MAMPOSSt technique to perform a joint maximum likelihood fit to the velocity dispersion profile of the BCG and to the velocity distribution of cluster member galaxies over a radial range from 1 kpc to the virial radius (r200 ≈ 2.7 Mpc). Results. We find a value of γDM = 0.99 ± 0.04 for the inner logarithmic slope of the DM density profile after marginalizing over all the other parameters of the mass and velocity anisotropy models. Moreover, the newly determined dynamical mass profile is found to be in excellent agreement with the mass density profiles obtained from the independent X-ray hydrostatic analysis based on deep Chandra data, as well as the strong and weak lensing analyses. Conclusions. Our value of the inner logarithmic slope of the DM density profile γDM is in very good agreement with predictions from cosmological CDM simulations. We will extend our analysis to more clusters in future works. If confirmed on a larger cluster sample, our result makes this DM model more appealing than alternative models.

scholarly journals A cosmologically consistent millicharged dark matter solution to the EDGES anomaly of possible string theory origin

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Amin Aboubrahim ◽  
Pran Nath ◽  
Zhu-Yao Wang
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Evolution Equations ◽  
Dirac Fermions ◽  
Absorption Signal ◽  
Hidden Sector ◽  
Coupled Equations ◽  
Dark Photon ◽  
Visible Sector ◽  
Physics Model

Abstract Analysis of EDGES data shows an absorption signal of the redshifted 21-cm line of atomic hydrogen at z ∼ 17 which is stronger than expected from the standard ΛCDM model. The absorption signal interpreted as brightness temperature T21 of the 21-cm line gives an amplitude of $$ -{500}_{-500}^{+200} $$ − 500 − 500 + 200 mK at 99% C.L. which is a 3.8σ deviation from what the standard ΛCDM cosmology gives. We present a particle physics model for the baryon cooling where a fraction of the dark matter resides in the hidden sector with a U(1) gauge symmetry and a Stueckelberg mechanism operates mixing the visible and the hidden sectors with the hidden sector consisting of dark Dirac fermions and dark photons. The Stueckelberg mass mixing mechanism automatically generates a millicharge for the hidden sector dark fermions providing a theoretical basis for using millicharged dark matter to produce the desired cooling of baryons seen by EDGES by scattering from millicharged dark matter. We compute the relic density of the millicharged dark matter by solving a set of coupled equations for the dark fermion and dark photon yields and for the temperature ratio of the hidden sector and the visible sector heat baths. For the analysis of baryon cooling, we analyze the evolution equations for the temperatures of baryons and millicharged dark matter as a function of the redshift. We exhibit regions of the parameter space which allow consistency with the EDGES data. We note that the Stueckelberg mechanism arises naturally in strings and the existence of a millicharge would point to its string origin.

scholarly journals Exploring extensions to the standard cosmological model and the impact of baryons on small scales

2020 ◽  
Vol 497 (3) ◽  
pp. 3809-3829 ◽  
Author(s):  
Sam G Stafford ◽  
Shaun T Brown ◽  
Ian G McCarthy ◽  
Andreea S Font ◽  
Andrew Robertson ◽  
...  
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Galaxy Formation ◽  
Mass Function ◽  
Density Fluctuations ◽  
Density Profiles ◽  
The Standard Model ◽  
Small Scales ◽  
Standard Cosmological Model ◽  
The Impact

ABSTRACT It has been claimed that the standard model of cosmology (ΛCDM) cannot easily account for a number of observations on relatively small scales, motivating extensions to the standard model. Here, we introduce a new suite of cosmological simulations that systematically explores three plausible extensions: warm dark matter, self-interacting dark matter, and a running of the scalar spectral index of density fluctuations. Current observational constraints are used to specify the additional parameters that come with these extensions. We examine a large range of observable metrics on small scales, including the halo mass function, density, and circular velocity profiles, the abundance of satellite subhaloes, and halo concentrations. For any given metric, significant degeneracies can be present between the extensions. In detail, however, the different extensions have quantitatively distinct mass and radial dependencies, suggesting that a multiprobe approach over a range of scales can be used to break the degeneracies. We also demonstrate that the relative effects on the radial density profiles in the different extensions (compared to the standard model) are converged down to significantly smaller radii than are the absolute profiles. We compare the derived cosmological trends with the impact of baryonic physics using the EAGLE and ARTEMIS simulations. Significant degeneracies are also present between baryonic physics and cosmological variations (with both having similar magnitude effects on some observables). Given the inherent uncertainties both in the modelling of galaxy formation physics and extensions to ΛCDM, a systematic and simultaneous exploration of both is strongly warranted.

Physics of superheavy dark matter in supergravity

2018 ◽  
Vol 27 (06) ◽  
pp. 1841011 ◽  
Author(s):  
Andrea Addazi ◽  
Antonino Marciano ◽  
Sergei V. Ketov ◽  
Maxim Yu. Khlopov
Keyword(s):  
Dark Matter ◽  
Gauge Symmetry ◽  
Particle Physics ◽  
Cold Dark Matter ◽  
Model Building ◽  
Density Fluctuations ◽  
String Compactifications ◽  
Matter Production ◽  
The Right ◽  
Superheavy Dark Matter

New trends in inflationary model building and dark matter production in supergravity are considered. Starobinsky inflation is embedded into [Formula: see text] supergravity, avoiding instability problems, when the inflaton belongs to a vector superfield associated with a [Formula: see text] gauge symmetry, instead of a chiral superfield. This gauge symmetry can be spontaneously broken by the super-Higgs mechanism resulting in a massive vector supermultiplet including the (real scalar) inflaton field. Both supersymmetry (SUSY) and the R-symmetry can also be spontaneously broken by the Polonyi mechanism at high scales close to the inflationary scale. In this case, Polonyi particles and gravitinos become superheavy, and can be copiously produced during inflation by the Schwinger mechanism sourced by the universe expansion. The Polonyi mass slightly exceeds twice the gravitino mass, so that Polonyi particles are unstable and decay into gravitinos. Considering the mechanisms of superheavy gravitino production, we find that the right amount of cold dark matter composed of gravitinos can be achieved. In our scenario, the parameter space of the inflaton potential is directly related to the dark matter one, providing a new unifying framework of inflation and dark matter genesis. A multi-superfield extension of the supergravity framework with a single (inflaton) superfield can result in a formation of primordial nonlinear structures like mini- and stellar-mass black holes, primordial nongaussianity, and the running spectral index of density fluctuations. This framework can be embedded into the SUSY GUTs inspired by heterotic string compactifications on Calabi–Yau three-folds, thus unifying particle physics with quantum gravity.

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