Effective dark matter power spectra inf(R)gravity

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

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Linear Power Spectra in Cold+Hot Dark Matter Models: Analytical Approximations and Applications

The Astrophysical Journal ◽

10.1086/177949 ◽

1996 ◽

Vol 471 (1) ◽

pp. 13-23 ◽

Cited By ~ 66

Author(s):

Chung‐Pei Ma

Keyword(s):

Dark Matter ◽

Power Spectra ◽

Analytical Approximations

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Anti-symmetric clustering signals in the observed power spectrum

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2021/12/003 ◽

2021 ◽

Vol 2021 (12) ◽

pp. 003

Author(s):

José Fonseca ◽

Chris Clarkson

Keyword(s):

Dark Matter ◽

Power Spectrum ◽

Euler Equation ◽

Large Scale ◽

Signal To Noise Ratio ◽

Power Spectra ◽

Large Scale Structure ◽

Scale Structure ◽

Signal To Noise ◽

Peculiar Velocities

Abstract In this paper, we study how to directly measure the effect of peculiar velocities in the observed angular power spectra. We do this by constructing a new anti-symmetric estimator of Large Scale Structure using different dark matter tracers. We show that the Doppler term is the major component of our estimator and we show that we can measure it with a signal-to-noise ratio up to ∼ 50 using a futuristic SKAO HI galaxy survey. We demonstrate the utility of this estimator by using it to provide constraints on the Euler equation.

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Impact of dark matter models on the EoR 21-cm signal bispectrum

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1768 ◽

2020 ◽

Vol 497 (3) ◽

pp. 2941-2953 ◽

Cited By ~ 1

Author(s):

Anchal Saxena ◽

Suman Majumdar ◽

Mohd Kamran ◽

Matteo Viel

Keyword(s):

Dark Matter ◽

Structure Formation ◽

Cold Dark Matter ◽

Power Spectra ◽

Neutral Hydrogen ◽

Cosmic Time ◽

Lower Number ◽

Neutral Fraction ◽

Small Scales ◽

Low Mass

ABSTRACT The nature of dark matter sets the timeline for the formation of first collapsed haloes and thus affects the sources of reionization. Here, we consider two different models of dark matter: cold dark matter (CDM) and thermal warm dark matter (WDM), and study how they impact the epoch of reionization (EoR) and its 21-cm observables. Using a suite of simulations, we find that in WDM scenarios, the structure formation on small scales gets suppressed, resulting in a smaller number of low-mass dark matter haloes compared to the CDM scenario. Assuming that the efficiency of sources in producing ionizing photons remains the same, this leads to a lower number of total ionizing photons produced at any given cosmic time, thus causing a delay in the reionization process. We also find visual differences in the neutral hydrogen (H i) topology and in 21-cm maps in case of the WDM compared to the CDM. However, differences in the 21-cm power spectra, at the same neutral fraction, are found to be small. Thus, we focus on the non-Gaussianity in the EoR 21-cm signal, quantified through its bispectrum. We find that the 21-cm bispectra (driven by the H i topology) are significantly different in WDM models compared to the CDM, even for the same mass-averaged neutral fractions. This establishes that the 21-cm bispectrum is a unique and promising way to differentiate between dark matter models, and can be used to constrain the nature of the dark matter in the future EoR observations.

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Constraining warm dark matter with cosmic shear power spectra

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2011/01/022 ◽

2011 ◽

Vol 2011 (01) ◽

pp. 022-022 ◽

Cited By ~ 25

Author(s):

Katarina Markovic ◽

Sarah Bridle ◽

Anže Slosar ◽

Jochen Weller

Keyword(s):

Dark Matter ◽

Power Spectra ◽

Cosmic Shear

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Effects of long-wavelength fluctuations in large galaxy surveys

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2194 ◽

2019 ◽

Vol 489 (2) ◽

pp. 1684-1696 ◽

Cited By ~ 1

Author(s):

Anatoly Klypin ◽

Francisco Prada

Keyword(s):

Dark Matter ◽

Finite Volume ◽

Average Power ◽

Power Spectra ◽

Covariance Matrices ◽

Galaxy Surveys ◽

Long Wavelength ◽

Ideal Situation ◽

Mass Functions ◽

The Ideal

ABSTRACT In order to capture as much information as possible large galaxies surveys have been increasing their volume and redshift depth. To face this challenge theory has responded by making cosmological simulations of huge computational volumes with equally increasing numbers of dark matter particles and supercomputing resources. Thus, it is taken for granted that the ideal situation is when a single computational box encompasses the whole volume of the observational survey, e.g. $\sim 50\, h^{-3}\,{\rm Gpc}^3$ for the DESI and Euclid surveys. Here we study the effects of missing long waves in a finite volume using several relevant statistics: the abundance of dark matter haloes, the probability distribution function (PDF), the correlation function and power spectrum, and covariance matrices. Finite volume effects can substantially modify the results if the computational volumes are less than $\sim (500\mbox{$\, h^{-1}$Mpc})^3$. However, the effects become extremely small and practically can be ignored when the box size exceeds ∼1 Gpc3. We find that the average power spectra of dark matter fluctuations show remarkable lack of dependence on the computational box size with less than 0.1 per cent differences between $1$ and $4\mbox{$\, h^{-1}\,$Gpc}$ boxes. No measurable differences are expected for the halo mass functions for these volumes. The covariance matrices are scaled trivially with volume, and small corrections due to supersample modes can be added. We conclude that there is no need to make those extremely large simulations when a box size of $1-1.5\mbox{$\, h^{-1}$Gpc}$ is sufficient to fulfil most of the survey science requirements.

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Angular Momentum Growth around Local Density Maxima

Symposium - International Astronomical Union ◽

10.1017/s0074180900136812 ◽

1988 ◽

Vol 130 ◽

pp. 552-552

Author(s):

A. F. Heavens ◽

J. A. Peacock

Keyword(s):

Dark Matter ◽

Angular Momentum ◽

Power Spectrum ◽

Total Angular Momentum ◽

Cold Dark Matter ◽

Local Density ◽

Probability Distributions ◽

Power Spectra ◽

Elliptical Galaxies ◽

Angular Momenta

We have calculated the growth of angular momentum about local density maxima at early epochs. We find that high peaks experience higher torques than low peaks, counteracting the short collapse time during which the high peaks can acquire angular momentum. Which effect is dominant depends on the perturbation power spectrum: for power spectra characteristic of both cold dark matter and hot dark matter, the effects nearly cancel, and the total angular momentum acquired by a collapsing object is almost independent of the height of the peak. Furthermore, the distributions of angular momenta acquired by collapsing protosystems are extremely broad, for all power spectra, far exceeding any modest differences between peaks of different height.These results indicate that it is not possible to account for the systematic differences in angular momentum properties of disk and elliptical galaxies simply by postulating that the latter arise from fluctuations of greater overdensity, contrary to some recent suggestions. The figure shows the probability distributions for the final angular momentum acquired by peaks of dimensionless height 1–4, for a power spectrum similar to cold dark matter. A fuller account of this work has been submitted to MNRAS.

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The lensing properties of subhaloes in massive elliptical galaxies in sterile neutrino cosmologies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3068 ◽

2019 ◽

Vol 491 (1) ◽

pp. 1295-1310 ◽

Cited By ~ 4

Author(s):

Giulia Despali ◽

Mark Lovell ◽

Simona Vegetti ◽

Robert A Crain ◽

Benjamin D Oppenheimer

Keyword(s):

Dark Matter ◽

Power Spectrum ◽

Galaxy Formation ◽

Cold Dark Matter ◽

Distribution Density ◽

Sterile Neutrino ◽

Power Spectra ◽

Mass Function ◽

Elliptical Galaxies ◽

Hydrodynamical Simulations

ABSTRACT We use high-resolution hydrodynamical simulations run with the EAGLE model of galaxy formation to study the differences between the properties of – and subsequently the lensing signal from – subhaloes of massive elliptical galaxies at redshift 0.2, in Cold and Sterile Neutrino (SN) Dark Matter models. We focus on the two 7 keV SN models that bracket the range of matter power spectra compatible with resonantly produced SN as the source of the observed 3.5 keV line. We derive an accurate parametrization for the subhalo mass function in these two SN models relative to cold dark matter (CDM), as well as the subhalo spatial distribution, density profile, and projected number density and the dark matter fraction in subhaloes. We create mock lensing maps from the simulated haloes to study the differences in the lensing signal in the framework of subhalo detection. We find that subhalo convergence is well described by a lognormal distribution and that signal of subhaloes in the power spectrum is lower in SN models with respect to CDM, at a level of 10–80 per cent, depending on the scale. However, the scatter between different projections is large and might make the use of power spectrum studies on the typical scales of current lensing images very difficult. Moreover, in the framework of individual detections through gravitational imaging a sample of ≃30 lenses with an average sensitivity of $M_{\rm {sub}} = 5 \times 10^{7}\, {\rm M}_{\odot}$ would be required to discriminate between CDM and the considered sterile neutrino models.

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