scholarly journals Reaching small scales with low-frequency imaging: applications to the Dark Ages

2020 ◽  
Vol 379 (2188) ◽  
pp. 20190571 ◽  
Author(s):  
L. K. Morabito ◽  
J. Silk
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Initial Conditions ◽  
Low Frequency ◽  
Integration Time ◽  
Observational Constraints ◽  
The Moon ◽  
Microwave Background ◽  
Matter Power Spectrum ◽  
Density Perturbations

The initial conditions for the density perturbations in the early Universe, which dictate the large-scale structure and distribution of galaxies we see today, are set during inflation. Measurements of primordial non-Gaussianity are crucial for distinguishing between different inflationary models. Current measurements of the matter power spectrum from the cosmic microwave background only constrain this on scales up to k  ∼ 0.1 Mpc −1 . Reaching smaller angular scales (higher values of k ) can provide new constraints on non-Gaussianity. A powerful way to do this is by measuring the HI matter power spectrum at z ≳ 30 . In this paper, we investigate what values of k can be reached for the Low-Frequency Array (LOFAR), which can achieve ≲ 1″ resolution at approximately 50 MHz. Combining this with a technique to isolate the spectrally smooth foregrounds to a wedge in k ∥ – k ⊥ space, we demonstrate what values of k we can feasibly reach within observational constraints. We find that LOFAR is approximately five orders of magnitude away from the desired sensitivity, for 10 years of integration time. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.

scholarly journals The escape fraction of ionizing photons during the Epoch of Reionization: observability with the Square Kilometre Array

2019 ◽  
Vol 487 (4) ◽  
pp. 5739-5752 ◽  
Author(s):  
Jacob Seiler ◽  
Anne Hutter ◽  
Manodeep Sinha ◽  
Darren Croton
Keyword(s):  
Power Spectrum ◽  
Galaxy Evolution ◽  
Optical Depth ◽  
Large Scale ◽  
Low Frequency ◽  
Integration Time ◽  
Square Kilometre Array ◽  
Exciting Opportunity ◽  
Functional Forms ◽  
The Impact

Abstract One of the most important parameters in characterizing the Epoch of Reionization, the escape fraction of ionizing photons, fesc, remains unconstrained both observationally and theoretically. With recent work highlighting the impact of galaxy-scale feedback on the instantaneous value of fesc, it is important to develop a model in which reionization is self-consistently coupled to galaxy evolution. In this work, we present such a model and explore how physically motivated functional forms of fesc affect the evolution of ionized hydrogen within the intergalactic medium. Using the 21 cm power spectrum evolution, we investigate the likelihood of observationally distinguishing between a constant fesc and other models that depend upon different forms of galaxy feedback. We find that changing the underlying connection between fesc and galaxy feedback drastically alters the large-scale 21 cm power. The upcoming Square Kilometre Array Low Frequency instrument possesses the sensitivity to differentiate between our models at a fixed optical depth, requiring only 200 h of integration time focused on redshifts z = 7.5–8.5. Generalizing these results to account for a varying optical depth will require multiple 800 h observations spanning redshifts z = 7–10. This presents an exciting opportunity to observationally constrain one of the most elusive parameters during the Epoch of Reionization.

scholarly journals Consistency relations for large-scale structures: Applications for the integrated Sachs-Wolfe effect and the kinematic Sunyaev-Zeldovich effect

2017 ◽  
Vol 606 ◽  
pp. A128 ◽  
Author(s):  
Luca Alberto Rizzo ◽  
David F. Mota ◽  
Patrick Valageas
Keyword(s):  
Power Spectrum ◽  
Equivalence Principle ◽  
Large Scale ◽  
Initial Conditions ◽  
Time Derivative ◽  
Matter Density ◽  
Microwave Background ◽  
Large Scale Structures ◽  
Cross Correlations ◽  
Scale Structures

Consistency relations of large-scale structures provide exact nonperturbative results for cross-correlations of cosmic fields in the squeezed limit. They only depend on the equivalence principle and the assumption of Gaussian initial conditions, and remain nonzero at equal times for cross-correlations of density fields with velocity or momentum fields, or with the time derivative of density fields. We show how to apply these relations to observational probes that involve the integrated Sachs-Wolfe effect or the kinematic Sunyaev-Zeldovich effect. In the squeezed limit, this allows us to express the three-point cross-correlations, or bispectra, of two galaxy or matter density fields, or weak lensing convergence fields, with the secondary cosmic microwave background distortion in terms of products of a linear and a nonlinear power spectrum. In particular, we find that cross-correlations with the integrated Sachs-Wolfe effect show a specific angular dependence. These results could be used to test the equivalence principle and the primordial Gaussianity, or to check the modeling of large-scale structures.

scholarly journals Exploring the effects of galaxy formation on matter clustering through a library of simulation power spectra

2019 ◽  
Vol 491 (2) ◽  
pp. 2424-2446 ◽  
Author(s):  
Marcel P van Daalen ◽  
Ian G McCarthy ◽  
Joop Schaye
Keyword(s):  
Power Spectrum ◽  
Galaxy Formation ◽  
Large Scale ◽  
Initial Conditions ◽  
Power Spectra ◽  
Relative Difference ◽  
Theoretical Understanding ◽  
Stellar Feedback ◽  
Matter Power Spectrum ◽  
Systems Simulation

ABSTRACT Upcoming weak lensing surveys require a detailed theoretical understanding of the matter power spectrum in order to derive accurate and precise cosmological parameter values. While galaxy formation is known to play an important role, its precise effects are currently unknown. We present a set of 92 matter power spectra from the OWLS, cosmo-OWLS, and BAryons and HAloes of MAssive Systems simulation suites, including different ΛCDM cosmologies, neutrino masses, subgrid prescriptions, and AGN feedback strengths. We conduct a detailed investigation of the dependence of the relative difference between the total matter power spectra in hydrodynamical and collisionless simulations on the effectiveness of stellar and AGN feedback, cosmology, and redshift. The strength of AGN feedback can greatly affect the power on a range of scales, while a lack of stellar feedback can greatly increase the effectiveness of AGN feedback on large scales. We also examine differences in the initial conditions of hydrodynamic and N-body simulations that can lead to an $\sim 1{{\ \rm per\ cent}}$ discrepancy in the large-scale power, and furthermore show our results to be insensitive to cosmic variance. We present an empirical model capable of predicting the effect of galaxy formation on the matter power spectrum at z = 0 to within $1{{\ \rm per\ cent}}$ for $k\lt 1\, h\, \mathrm{Mpc}^{-1}$, given only the mean baryon fraction in galaxy groups. Differences in group baryon fractions can also explain the quantitative disagreement between predictions from the literature. All total and dark matter only power spectra in this library will be made publicly available at powerlib.strw.leidenuniv.nl.

scholarly journals SEARCHING FOR DARK MATTER ISOCURVATURE INITIAL CONDITIONS WITH N-BODY SIMULATIONS

2012 ◽  
Vol 21 (03) ◽  
pp. 1250021
Author(s):  
JIE LIU
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Initial Conditions ◽  
Mass Function ◽  
Matter Power Spectrum ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Best Fit ◽  
Isocurvature Perturbations

Small fraction of isocurvature perturbations may exist and correlate with adiabatic perturbations in the primordial perturbations. Naively switching off isocurvature perturbations may lead to biased results. We study the effect of dark matter isocurvature on the structure formation through N-body simulations. From the best-fit values, we run four sets of simulation with different initial conditions and different box sizes. We find that, if the fraction of dark matter isocurvature is small, we cannot detect its signal through matter power spectrum and two-point correlation function with large scale survey. However, the halo mass function can give an obvious signal. Compared to 5% difference on matter power spectrum, it can get 37% at z = 3 on halo mass function. This indicates that future high precise cluster count experiment can give stringent constraints on dark matter isocurvature perturbations.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

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.

scholarly journals Anisotropy of the Microwave Background and Biased Galaxy Formation

1988 ◽  
Vol 130 ◽  
pp. 43-50
Author(s):  
Nick Kaiser
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Microwave Background ◽  
Galaxy Clustering ◽  
Clear View ◽  
Hot Gas ◽  
Density Perturbations ◽  
The Universe ◽  
Theoretical Developments

Fluctuations in the microwave background will have been imprinted at z ≃ 1000, when the photons and the plasma decoupled. On angular scales greater than a few degrees these fluctuations provide a clear view of any primordial density perturbations, and therefore a clean test of theories which invoke such fluctuations from which to form the structure we see in the universe. On smaller angular scales the predictions are less certain: reionization of the gas may modify the spectrum of the primordial fluctuations, and secondary fluctuations may be generated.Here I shall review some recent theoretical developments. A brief survey is made of the currently popular theories for the primordial perturbations, with emphasis on the predictions for large scale anisotropy. One major uncetainty in the predictions arises from the normalisation of the fluctuations to e.g. galaxy clustering, and much attention is given to the question of ‘biased’ galaxy formation. The effect of reionization on the primordial fluctuations is discussed, as is the anisotropy generated from scattering off hot gas in clusters, groups and galaxies.

scholarly journals Cosmic calibration: Constraints from the matter power spectrum and the cosmic microwave background

2007 ◽  
Vol 76 (8) ◽  
Author(s):  
Salman Habib ◽  
Katrin Heitmann ◽  
David Higdon ◽  
Charles Nakhleh ◽  
Brian Williams
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Matter Power Spectrum

scholarly journals NATURAL INFLATION, PLANCK SCALE PHYSICS AND OSCILLATING PRIMORDIAL SPECTRUM

2005 ◽  
Vol 14 (08) ◽  
pp. 1347-1364 ◽  
Author(s):  
XIULIAN WANG ◽  
BO FENG ◽  
MINGZHE LI ◽  
XUE-LEI CHEN ◽  
XINMIN ZHANG
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
High Frequency ◽  
Large Scale ◽  
Planck Scale ◽  
Microwave Background ◽  
Precision Data ◽  
Inflation Model ◽  
High Precision Data ◽  
Planck Scale Physics

In the "natural inflation" model, the inflaton potential is periodic. We show that Planck scale physics may induce corrections to the inflaton potential, which is also periodic with a greater frequency. Such high frequency corrections produce oscillating features in the primordial fluctuation power spectrum, which are not entirely excluded by the current observations and may be detectable in high precision data of cosmic microwave background (CMB) anisotropy and large scale structure (LSS) observations.

scholarly journals Towards Understanding the Large-Scale Structure?

1987 ◽  
Vol 124 ◽  
pp. 415-432
Author(s):  
Avishai Dekel
Keyword(s):  
Dark Matter ◽  
First Principles ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Ad Hoc ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Observational Constraints ◽  
Microwave Background ◽  
Satisfactory Theory

Although some theories, such as that of cold dark matter, are quite successful in explaining certain aspects of the formation of structure, we seem not to approach a satisfactory theory which can easily account for all the observational constraints on all scales. Most difficult to explain are the indicated clustering of clusters and bulk velocities on very large scales, when considered together with the structure on galactic scales and the isotropy of the microwave background. If these observations are correct, the only scenarios that can work are hybrids of certain sorts, which involve somewhat ad hoc choices of parameters; they are not the theories that would have emerged naturally from first principles, and they do not satisfy the criteria of simplicity and elegancy. I will discuss the currently popular scenarios and the apparent difficulties they face.

scholarly journals Power spectrum response of large-scale structure in 1D and in 3D: tests of prescriptions for post-collapse dynamics

2020 ◽  
Vol 499 (2) ◽  
pp. 1769-1787
Author(s):  
Anaëlle Halle ◽  
Takahiro Nishimichi ◽  
Atsushi Taruya ◽  
Stéphane Colombi ◽  
Francis Bernardeau
Keyword(s):  
Power Spectrum ◽  
Response Function ◽  
Large Scale ◽  
Initial Conditions ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Adaptive Smoothing ◽  
Single Stream ◽  
Non Linear ◽  
Spectrum Response

ABSTRACT The power spectrum response function of the large-scale structure of the Universe describes how the evolved power spectrum is modified by a small change in initial power through non-linear mode coupling of gravitational evolution. It was previously found that the response function for the coupling from small to large scales is strongly suppressed in amplitude, especially at late times, compared to predictions from perturbation theory (PT) based on the single-stream approximation. One obvious explanation for this is that PT fails to describe the dynamics beyond shell crossing. We test this idea by comparing measurements in N-body simulations to prescriptions based on PT but augmented with adaptive smoothing to account for the formation of non-linear structures of various sizes in the multistream regime. We first start with one-dimensional (1D) cosmology, where the Zel’dovich approximation provides the exact solution in the single-stream regime. Similarly to the three-dimensional (3D) case, the response function of the large-scale modes exhibits a strong suppression in amplitude at small scales that cannot be explained by the Zel’dovich solution alone. However, by performing adaptive smoothing of initial conditions to identify haloes of different sizes and solving approximately post-collapse dynamics in the three-stream regime, agreement between theory and simulations drastically improves. We extend our analyses to the 3D case using the pinocchio algorithm, in which similar adaptive smoothing is implemented on the Lagrangian PT fields to identify haloes and is combined with a spherical halo prescription to account for post-collapse dynamics. Again, a suppression is found in the coupling between small- and large-scale modes and the agreement with simulations is improved.

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