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 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 On the road to per cent accuracy – II. Calibration of the non-linear matter power spectrum for arbitrary cosmologies

2019 ◽  
Vol 490 (4) ◽  
pp. 4826-4840 ◽  
Author(s):  
Benjamin Giblin ◽  
Matteo Cataneo ◽  
Ben Moews ◽  
Catherine Heymans
Keyword(s):  
Power Spectrum ◽  
Initial Conditions ◽  
Power Spectra ◽  
Linear Regime ◽  
The Road ◽  
Matter Power Spectrum ◽  
Non Linear ◽  
Standard Cosmological Model ◽  
Massive Neutrinos ◽  
On The Road

ABSTRACT We introduce an emulator approach to predict the non-linear matter power spectrum for broad classes of beyond-ΛCDM cosmologies, using only a suite of ΛCDM N-body simulations. By including a range of suitably modified initial conditions in the simulations, and rescaling the resulting emulator predictions with analytical ‘halo model reactions’, accurate non-linear matter power spectra for general extensions to the standard ΛCDM model can be calculated. We optimize the emulator design by substituting the simulation suite with non-linear predictions from the standard halofit tool. We review the performance of the emulator for artificially generated departures from the standard cosmology as well as for theoretically motivated models, such as f(R) gravity and massive neutrinos. For the majority of cosmologies we have tested, the emulator can reproduce the matter power spectrum with errors ${\lesssim}1{{\ \rm per\ cent}}$ deep into the highly non-linear regime. This work demonstrates that with a well-designed suite of ΛCDM simulations, extensions to the standard cosmological model can be tested in the non-linear regime without any reliance on expensive beyond-ΛCDM simulations.

scholarly journals Power spectrum of halo intrinsic alignments in simulations

2020 ◽  
Vol 501 (1) ◽  
pp. 833-852
Author(s):  
Toshiki Kurita ◽  
Masahiro Takada ◽  
Takahiro Nishimichi ◽  
Ryuichi Takahashi ◽  
Ken Osato ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Signal To Noise Ratio ◽  
Cosmological Parameters ◽  
Three Dimensional ◽  
Power Spectra ◽  
Acoustic Oscillations ◽  
Matter Power Spectrum ◽  
Sample Covariance ◽  
Non Linear

ABSTRACT We use a suite of N-body simulations to study intrinsic alignments (IA) of halo shapes with the surrounding large-scale structure in the ΛCDM model. For this purpose, we develop a novel method to measure multipole moments of the three-dimensional power spectrum of the E-mode field of halo shapes with the matter/halo distribution, $P_{\delta E}^{(\ell)}(k)$ (or $P^{(\ell)}_{{\rm h}E}$), and those of the auto-power spectrum of the E-mode, $P^{(\ell)}_{EE}(k)$, based on the E/B-mode decomposition. The IA power spectra have non-vanishing amplitudes over the linear to non-linear scales, and the large-scale amplitudes at k ≲ 0.1 h−1 Mpc are related to the matter power spectrum via a constant coefficient (AIA), similar to the linear bias parameter of galaxy or halo density field. We find that the cross- and auto-power spectra PδE and PEE at non-linear scales, k ≳ 0.1 h−1 Mpc, show different k-dependences relative to the matter power spectrum, suggesting a violation of the non-linear alignment model commonly used to model contaminations of cosmic shear signals. The IA power spectra exhibit baryon acoustic oscillations, and vary with halo samples of different masses, redshifts, and cosmological parameters (Ωm, S8). The cumulative signal-to-noise ratio for the IA power spectra is about 60 per cent of that for the halo density power spectrum, where the super-sample covariance is found to give a significant contribution to the total covariance. Thus our results demonstrate that the IA power spectra of galaxy shapes, measured from imaging and spectroscopic surveys for an overlapping area of the sky, can be used to probe the underlying matter power spectrum, the primordial curvature perturbations, and cosmological parameters, in addition to the standard galaxy density power spectrum.

scholarly journals Explicit Bayesian treatment of unknown foreground contaminations in galaxy surveys

2019 ◽  
Vol 624 ◽  
pp. A115 ◽  
Author(s):  
Natalia Porqueres ◽  
Doogesh Kodi Ramanah ◽  
Jens Jasche ◽  
Guilhem Lavaux
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Scale Effects ◽  
Power Spectra ◽  
Matter Density ◽  
Data Set ◽  
Dark Matter Density ◽  
Matter Power Spectrum ◽  
Robust Likelihood

The treatment of unknown foreground contaminations will be one of the major challenges for galaxy clustering analyses of coming decadal surveys. These data contaminations introduce erroneous large-scale effects in recovered power spectra and inferred dark matter density fields. In this work, we present an effective solution to this problem in the form of a robust likelihood designed to account for effects due to unknown foreground and target contaminations. Conceptually, this robust likelihood marginalizes over the unknown large-scale contamination amplitudes. We showcase the effectiveness of this novel likelihood via an application to a mock SDSS-III data set subject to dust extinction contamination. In order to illustrate the performance of our proposed likelihood, we infer the underlying dark-matter density field and reconstruct the matter power spectrum, being maximally agnostic about the foregrounds. The results are compared to those of an analysis with a standard Poissonian likelihood, as typically used in modern large-scale structure analyses. While the standard Poissonian analysis yields excessive power for large-scale modes and introduces an overall bias in the power spectrum, our likelihood provides unbiased estimates of the matter power spectrum over the entire range of Fourier modes considered in this work. Further, we demonstrate that our approach accurately accounts for and corrects the effects of unknown foreground contaminations when inferring three-dimensional density fields. Robust likelihood approaches, as presented in this work, will be crucial to control unknown systematic error and maximize the outcome of the decadal surveys.

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 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 EDGE: a new approach to suppressing numerical diffusion in adaptive mesh simulations of galaxy formation

2020 ◽  
Vol 501 (2) ◽  
pp. 1755-1765
Author(s):  
Andrew Pontzen ◽  
Martin P Rey ◽  
Corentin Cadiou ◽  
Oscar Agertz ◽  
Romain Teyssier ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Adaptive Mesh Refinement ◽  
Large Scale ◽  
Initial Conditions ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Morphological Structure ◽  
Adaptive Mesh ◽  
Numerical Diffusion

ABSTRACT We introduce a new method to mitigate numerical diffusion in adaptive mesh refinement (AMR) simulations of cosmological galaxy formation, and study its impact on a simulated dwarf galaxy as part of the ‘EDGE’ project. The target galaxy has a maximum circular velocity of $21\, \mathrm{km}\, \mathrm{s}^{-1}$ but evolves in a region that is moving at up to $90\, \mathrm{km}\, \mathrm{s}^{-1}$ relative to the hydrodynamic grid. In the absence of any mitigation, diffusion softens the filaments feeding our galaxy. As a result, gas is unphysically held in the circumgalactic medium around the galaxy for $320\, \mathrm{Myr}$, delaying the onset of star formation until cooling and collapse eventually triggers an initial starburst at z = 9. Using genetic modification, we produce ‘velocity-zeroed’ initial conditions in which the grid-relative streaming is strongly suppressed; by design, the change does not significantly modify the large-scale structure or dark matter accretion history. The resulting simulation recovers a more physical, gradual onset of star formation starting at z = 17. While the final stellar masses are nearly consistent ($4.8 \times 10^6\, \mathrm{M}_{\odot }$ and $4.4\times 10^6\, \mathrm{M}_{\odot }$ for unmodified and velocity-zeroed, respectively), the dynamical and morphological structure of the z = 0 dwarf galaxies are markedly different due to the contrasting histories. Our approach to diffusion suppression is suitable for any AMR zoom cosmological galaxy formation simulations, and is especially recommended for those of small galaxies at high redshift.

scholarly journals Anti-symmetric clustering signals in the observed power spectrum

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.

scholarly journals ETHOS – an effective theory of structure formation: formation of the first haloes and their stars

2019 ◽  
Vol 485 (4) ◽  
pp. 5474-5489 ◽  
Author(s):  
Mark R Lovell ◽  
Jesús Zavala ◽  
Mark Vogelsberger
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxy ◽  
Mass Scale ◽  
Effective Theory ◽  
Matter Power Spectrum ◽  
Hydrodynamical Simulations ◽  
Stellar Masses

Abstract A cut-off in the linear matter power spectrum at dwarf galaxy scales has been shown to affect the abundance, formation mechanism and age of dwarf haloes, and their galaxies at high and low redshifts. We use hydrodynamical simulations of galaxy formation within the ETHOS framework in a benchmark model that has such a cut-off and that has been shown to be an alternative to the cold dark matter (CDM) model that alleviates its dwarf-scale challenges. We show how galaxies in this model form differently to CDM, on a halo-by-halo basis, at redshifts z ≥ 6. We show that when CDM haloes with masses around the ETHOS half-mode mass scale are resimulated with the ETHOS matter power spectrum, they form with 50 per cent less mass than their CDM counterparts due to their later formation times, yet they retain more of their gas reservoir due to the different behaviour of gas and dark matter during the monolithic collapse of the first haloes in models with a galactic-scale cut-off. As a result, galaxies in ETHOS haloes near the cut-off scale grow rapidly between z = 10 and 6 and by z = 6 end up having very similar stellar masses, higher gas fractions and higher star formation rates relative to their CDM counterparts. We highlight these differences by making predictions for how the number of galaxies with old stellar populations is suppressed in ETHOS for both z = 6 galaxies and for gas-poor Local Group fossil galaxies. Interestingly, we find an age gradient in ETHOS between galaxies that form in high- and low-density environments.

scholarly journals A Model for the Sequence of Elliptical Galaxies

1987 ◽  
Vol 117 ◽  
pp. 367-367
Author(s):  
Rosemary F. G. Wyse ◽  
Bernard J. T. Jones
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Density Fluctuations ◽  
Analytic Approximation ◽  
Non Linear

We present a simple model for the formation of elliptical galaxies, based on a binary clustering hierarchy of dark matter, the chemical enrichment of the gas at each level being controlled by supernovae. The initial conditions for the non-linear phases of galaxy formation are set by the post-recombination power spectrum of density fluctuations. We investigate two models for this power spectrum - the first is a straightforward power law, |δk|2 ∝ kn, and the second is Peeble's analytic approximation to the emergent spectrum in a universe dominated by cold dark matter. The normalisation is chosen such that on some scale, say M ∼ 1012M⊙, the objects that condense out have properties - radius and velocity dispersion - resembling ‘typical’ galaxies. There is some ambiguity in this due to the poorly determined mass-to-light ratio of a typical elliptical galaxy — we look at two normalisations, σ1D ∼ 350kms−1 and σ1D ∼ 140kms−1. The choice determines which of Compton cooling or hydrogen cooling is more important during the galaxy formation period. The non-linear behaviour of the perturbations is treated by the homogeneous sphere approximation.

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