The high-redshift neutral hydrogen signature of an anisotropic matter power spectrum

ABSTRACT We propose two effective parameters that fully characterize galactic-scale structure formation at high redshifts (z ≳ 5) for a variety of dark matter (DM) models that have a primordial cutoff in the matter power spectrum. Our description is within the recently proposed ETHOS framework and includes standard thermal warm DM (WDM) and models with dark acoustic oscillations (DAOs). To define and explore this parameter space, we use high-redshift zoom-in simulations that cover a wide range of non-linear scales from those where DM should behave as CDM (k ∼ 10 h Mpc−1), down to those characterized by the onset of galaxy formation (k ∼ 500 h Mpc−1). We show that the two physically motivated parameters hpeak and kpeak, the amplitude and scale of the first DAO peak, respectively, are sufficient to parametrize the linear matter power spectrum and classify the DM models as belonging to effective non-linear structure formation regions. These are defined by their relative departure from cold DM (kpeak → ∞) and WDM (hpeak = 0) according to the non-linear matter power spectrum and halo mass function. We identify a region where the DAOs still leave a distinct signature from WDM down to z = 5, while a large part of the DAO parameter space is shown to be degenerate with WDM. Our framework can then be used to seamlessly connect a broad class of particle DM models to their structure formation properties at high redshift without the need of additional N-body simulations.

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Intensity mapping as a probe of axion dark matter

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3300 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3162-3177

Author(s):

Jurek B Bauer ◽

David J E Marsh ◽

Renée Hložek ◽

Hamsa Padmanabhan ◽

Alex Laguë

Keyword(s):

Dark Matter ◽

Power Spectrum ◽

Neutral Hydrogen ◽

Matrix Formalism ◽

Intensity Mapping ◽

Matter Power Spectrum ◽

Wide Range ◽

Non Linear ◽

Order Of Magnitude ◽

Magnitude Improvement

ABSTRACT We consider intensity mapping (IM) of neutral hydrogen (H i) in the redshift range 0 ≲ z ≲ 3 employing a halo model approach where H i is assumed to follow the distribution of dark matter (DM) haloes. If a portion of the DM is composed of ultralight axions, then the abundance of haloes is changed compared to cold DM below the axion Jeans mass. With fixed total H i density, $\Omega _{\rm H\, \rm {\small I}}$, assumed to reside entirely in haloes, this effect introduces a scale-independent increase in the H i power spectrum on scales above the axion Jeans scale, which our model predicts consistent with N-body simulations. Lighter axions introduce a scale-dependent feature even on linear scales due to its suppression of the matter power spectrum near the Jeans scale. We use the Fisher matrix formalism to forecast the ability of future H i surveys to constrain the axion fraction of DM and marginalize over astrophysical and model uncertainties. We find that a HIRAX-like survey is a very reliable IM survey configuration, being affected minimally by uncertainties due to non-linear scales, while the SKA1MID configuration is the most constraining as it is sensitive to non-linear scales. Including non-linear scales and combining a SKA1MID-like IM survey with the Simons Observatory CMB, the benchmark ‘fuzzy DM’ model with ma = 10−22 eV can be constrained at few per cent. This is almost an order of magnitude improvement over current limits from the Ly α forest. For lighter ULAs, this limit improves below 1 per cent, and allows the possibility to test the connection between axion models and the grand unification scale across a wide range of masses.

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High-redshift radio galaxies: a potential new source of 21-cm fluctuations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3091 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5993-6008

Author(s):

Itamar Reis ◽

Anastasia Fialkov ◽

Rennan Barkana

Keyword(s):

Power Spectrum ◽

High Redshift ◽

Neutral Hydrogen ◽

Radio Sources ◽

Radiation Background ◽

Low Frequencies ◽

Standard Case ◽

High Redshift Galaxies ◽

Radio Background ◽

Redshift Galaxies

ABSTRACT Radio sources are expected to have formed at high redshifts, producing an excess radiation background above the cosmic microwave background (CMB) at low frequencies. Their effect on the redshifted 21-cm signal of neutral hydrogen is usually neglected, as it is assumed that the associated background is small. Recently, an excess radio background has been proposed as a possible explanation for the unusually strong 21-cm signal reported by EDGES. As a result, the implications of a smooth and extremely strong excess radio background on both the sky-averaged 21-cm signal and its fluctuations have been considered. Here, we take into account the inhomogeneity of the radio background created by a population of high-redshift galaxies and show that it adds a new type of 21-cm fluctuations to the well-known contributions of density, velocity, Ly α coupling, heating, and reionization. We find that a population of high-redshift galaxies even with a moderately enhanced radio efficiency (unrelated to the EDGES result) can have a significant effect on the 21-cm power spectrum and global signal. For models that can explain the EDGES data, we show that the 21-cm power spectrum at z ∼ 17 is enhanced by up to two orders of magnitude compared to the CMB-only standard case, with a significantly modified shape and time evolution due to radio fluctuations. These fluctuations are within reach of upcoming radio interferometers. We also find that these models can be significantly constrained by current and future observations of radio sources.

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Comparison of Observing Modes for Statistical Estimation of the 21 cm Signal from the Epoch of Reionisation

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2014.23 ◽

2014 ◽

Vol 31 ◽

Cited By ~ 12

Author(s):

Cathryn M. Trott

Keyword(s):

Power Spectrum ◽

Signal To Noise Ratio ◽

High Redshift ◽

Power Spectra ◽

Low Frequency ◽

Neutral Hydrogen ◽

Beam Shape ◽

Drift Scan ◽

Murchison Widefield Array ◽

Aperture Arrays

AbstractNoise considerations for experiments that aim to statistically estimate the 21 cm signal from high redshift neutral hydrogen during the Epoch of Reionisation (EoR) using interferometric data are typically computed assuming a tracked observation, where the telescope pointing centre and instrument phase centre are the same over the observation. Current low frequency interferometers use aperture arrays of fixed dipoles, which are steered electronically on the sky, and have different properties to mechanically-steered single apertures, such as reduced sensitivity away from zenith, and discrete pointing positions on the sky. These properties encourage the use of two additional observing modes: (1) zenith drift, where the pointing centre remains fixed at the zenith, and the phase centre tracks the sky, and (2) drift + shift, a hybrid mode where the telescope uses discrete pointing centres, and the sky drifts during each fixed pointing. These three observing modes view the sky differently, and therefore yield different uncertainties in the power spectrum according to the balance of radiometric noise and cosmic variance. The coherence of measurements made by the instrument in these modes dictates the optimal reduction in thermal noise by combination of coherent modes, and the reduction in cosmic variance by combination of incoherent modes (views of different patches of the sky). Along with calibration and instrument stability considerations, the balance between these noise components provides one measure for the utility of these three modes for measuring a statistical signature of the EoR signal. We provide a general framework for estimating the uncertainty in the power spectrum for a given observing mode, telescope beam shape, and interferometer antenna distribution. We then apply this framework to the Murchison Widefield Array (MWA) using an analysis of the two-dimensional (2D) and one-dimensional (1D) power spectra for 900 hours of observing. We demonstrate that zenith drift scans can yield marginally lower uncertainty in the signal power compared with tracked scans for the MWA EoR experiment, and that moderately higher signal-to-noise ratio (S/N) estimates of the amplitude (3%) and slope (1%) of the 1D power spectrum are accessible, translating directly into a reduction in the required observing time to reach the same estimation precision. We find that the additional sensitivity of pointing at zenith, and the reduction in cosmic variance available with a zenith drift scan, makes this an attractive observing mode for current and future arrays.

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Cosmological model parameter dependence of the matter power spectrum covariance from the DEUS-PUR Cosmo simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3444 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2532-2542

Author(s):

Linda Blot ◽

Pier-Stefano Corasaniti ◽

Yann Rasera ◽

Shankar Agarwal

Keyword(s):

Dark Energy ◽

Power Spectrum ◽

Cold Dark Matter ◽

Matter Density ◽

Density Fluctuations ◽

Matrix Analysis ◽

Model Parameter ◽

Matter Power Spectrum ◽

Non Gaussian ◽

The Impact

ABSTRACT Future galaxy surveys will provide accurate measurements of the matter power spectrum across an unprecedented range of scales and redshifts. The analysis of these data will require one to accurately model the imprint of non-linearities of the matter density field. In particular, these induce a non-Gaussian contribution to the data covariance that needs to be properly taken into account to realize unbiased cosmological parameter inference analyses. Here, we study the cosmological dependence of the matter power spectrum covariance using a dedicated suite of N-body simulations, the Dark Energy Universe Simulation–Parallel Universe Runs (DEUS-PUR) Cosmo. These consist of 512 realizations for 10 different cosmologies where we vary the matter density Ωm, the amplitude of density fluctuations σ8, the reduced Hubble parameter h, and a constant dark energy equation of state w by approximately $10{{\ \rm per\ cent}}$. We use these data to evaluate the first and second derivatives of the power spectrum covariance with respect to a fiducial Λ-cold dark matter cosmology. We find that the variations can be as large as $150{{\ \rm per\ cent}}$ depending on the scale, redshift, and model parameter considered. By performing a Fisher matrix analysis we explore the impact of different choices in modelling the cosmological dependence of the covariance. Our results suggest that fixing the covariance to a fiducial cosmology can significantly affect the recovered parameter errors and that modelling the cosmological dependence of the variance while keeping the correlation coefficient fixed can alleviate the impact of this effect.

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Demonstrating the Tapered Gridded Estimator (TGE) for the Cosmological HI 21-cm Power Spectrum using 150 MHz GMRT observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3831 ◽

2020 ◽

Author(s):

Srijita Pal ◽

Somnath Bharadwaj ◽

Abhik Ghosh ◽

Samir Choudhuri

Keyword(s):

Power Spectrum ◽

Unbiased Estimate ◽

Power Spectra ◽

Neutral Hydrogen ◽

Statistical Error ◽

Temperature Fluctuations ◽

Radio Frequency Interference ◽

Rectangular Region ◽

Angular Power Spectrum ◽

The Mean

Abstract We apply the Tapered Gridded Estimator (TGE) for estimating the cosmological 21-cm power spectrum from 150 MHz GMRT observations which corresponds to the neutral hydrogen (HI) at redshift z = 8.28. Here TGE is used to measure the Multi-frequency Angular Power Spectrum (MAPS) Cℓ(Δν) first, from which we estimate the 21-cm power spectrum P(k⊥, k∥). The data here are much too small for a detection, and the aim is to demonstrate the capabilities of the estimator. We find that the estimated power spectrum is consistent with the expected foreground and noise behaviour. This demonstrates that this estimator correctly estimates the noise bias and subtracts this out to yield an unbiased estimate of the power spectrum. More than $47\%$ of the frequency channels had to be discarded from the data owing to radio-frequency interference, however the estimated power spectrum does not show any artifacts due to missing channels. Finally, we show that it is possible to suppress the foreground contribution by tapering the sky response at large angular separations from the phase center. We combine the k modes within a rectangular region in the ‘EoR window’ to obtain the spherically binned averaged dimensionless power spectra Δ2(k) along with the statistical error σ associated with the measured Δ2(k). The lowest k-bin yields Δ2(k) = (61.47)2 K2 at k = 1.59 Mpc−1, with σ = (27.40)2 K2. We obtain a 2 σ upper limit of (72.66)2 K2 on the mean squared HI 21-cm brightness temperature fluctuations at k = 1.59 Mpc−1.

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On the road to per cent accuracy – III. Non-linear reaction of the matter power spectrum to massive neutrinos

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3189 ◽

2019 ◽

Vol 491 (3) ◽

pp. 3101-3107 ◽

Cited By ~ 4

Author(s):

M Cataneo ◽

J D Emberson ◽

D Inman ◽

J Harnois-Déraps ◽

C Heymans

Keyword(s):

Power Spectrum ◽

Cold Dark Matter ◽

New Physics ◽

Model Reaction ◽

Matter Power Spectrum ◽

Non Linear ◽

Cent Level ◽

Massive Neutrinos ◽

On The Road ◽

Total Matter

ABSTRACT We analytically model the non-linear effects induced by massive neutrinos on the total matter power spectrum using the halo model reaction framework of Cataneo et al. In this approach, the halo model is used to determine the relative change to the matter power spectrum caused by new physics beyond the concordance cosmology. Using standard fitting functions for the halo abundance and the halo mass–concentration relation, the total matter power spectrum in the presence of massive neutrinos is predicted to per cent-level accuracy, out to $k=10 \,{ h}\,{\rm Mpc}^{-1}$. We find that refining the prescriptions for the halo properties using N-body simulations improves the recovered accuracy to better than 1 per cent. This paper serves as another demonstration for how the halo model reaction framework, in combination with a single suite of standard Λ cold dark matter (ΛCDM) simulations, can recover per cent-level accurate predictions for beyond ΛCDM matter power spectra, well into the non-linear regime.

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