Dark Matter searches through cross-correlations of gamma rays with neutral-hydrogen intensity mapping

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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Beyond ΛCDM with H i intensity mapping: robustness of cosmological constraints in the presence of astrophysics

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1663 ◽

2020 ◽

Vol 496 (4) ◽

pp. 4115-4126 ◽

Cited By ~ 2

Author(s):

Stefano Camera ◽

Hamsa Padmanabhan

Keyword(s):

Dark Matter ◽

Modified Gravity ◽

Cosmological Parameters ◽

Neutral Hydrogen ◽

Temperature Fluctuations ◽

Dark Matter Halo ◽

Cosmological Constraints ◽

Intensity Mapping ◽

Standard Cosmological Model ◽

First Time

ABSTRACT Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (H i) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of the standard cosmological model, such as modified gravity and primordial non-Gaussianity, taking self-consistently into account. The present constraints on the astrophysics of H i clustering in the treatment of the brightness temperature fluctuations. To understand the boundaries within which results thus obtained can be considered reliable, we examine the robustness of cosmological parameter estimation performed via studies of 21-cm intensity mapping, against our knowledge of the astrophysical processes leading to H i clustering. Modelling of astrophysical effects affects cosmological observables through the relation linking the overall H i mass in a bound object, to the mass of the underlying dark matter halo that hosts it. We quantify the biases in estimates of standard cosmological parameters and those describing modified gravity and primordial non-Gaussianity that are obtained if one misconceives the slope of the relation between H i mass and halo mass, or the lower virial velocity cut-off for a dark matter halo to be able to host H i. Remarkably, we find that astrophysical uncertainties will not affect searches for primordial non-Gaussianity – one of the strongest science cases for H i intensity mapping – despite the signal being deeply linked to the H i bias.

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Impact of foregrounds on H i intensity mapping cross-correlations with optical surveys

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1916 ◽

2019 ◽

Vol 488 (4) ◽

pp. 5452-5472 ◽

Cited By ~ 11

Author(s):

Steven Cunnington ◽

Laura Wolz ◽

Alkistis Pourtsidou ◽

David Bacon

Keyword(s):

Neutral Hydrogen ◽

Optical Data ◽

Line Of Sight ◽

Redshift Distribution ◽

Intensity Mapping ◽

Fast Independent Component Analysis ◽

Cross Correlations ◽

The Cross ◽

The Impact ◽

Optical Surveys

ABSTRACT The future of precision cosmology could benefit from cross-correlations between intensity maps of unresolved neutral hydrogen (H i) and more conventional optical galaxy surveys. A major challenge that needs to be overcome is removing the 21cm foreground emission that contaminates the cosmological H i signal. Using N-body simulations, we simulate H i intensity maps and optical catalogues that share the same underlying cosmology. Adding simulated foreground contamination and using state-of-the-art reconstruction techniques, we investigate the impacts that 21cm foregrounds and other systematics have on these cross-correlations. We find that the impact a Fast Independent Component Analysis 21cm foreground clean has on the cross-correlations with spectroscopic optical surveys with well-constrained redshifts is minimal. However, problems arise when photometric surveys are considered: We find that a redshift uncertainty σz ≥ 0.04 causes significant degradation in the cross-power spectrum signal. We diagnose the main root of these problems, which relates to arbitrary amplitude changes along the line of sight in the intensity maps caused by the foreground clean and suggest solutions that should be applicable to real data. These solutions involve a reconstruction of the line-of-sight temperature means using the available overlapping optical data along with an artificial extension to the H i data through redshift to address edge effects. We then put these solutions through a further test in a mock experiment that uses a clustering-based redshift estimation technique to constrain the photometric redshifts of the optical sample. We find that with our suggested reconstruction, cross-correlations can be utilized to make an accurate prediction of the optical redshift distribution.

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Synergies across the spectrum for particle dark matter indirect detection: how HI intensity mapping meets gamma rays

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2020/07/044 ◽

2020 ◽

Vol 2020 (07) ◽

pp. 044-044

Author(s):

Elena Pinetti ◽

Stefano Camera ◽

Nicolao Fornengo ◽

Marco Regis

Keyword(s):

Dark Matter ◽

Gamma Rays ◽

Indirect Detection ◽

Intensity Mapping ◽

Particle Dark Matter

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The degeneracy between primordial non-Gaussianity and foregrounds in 21 cm intensity mapping experiments

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2986 ◽

2020 ◽

Vol 499 (3) ◽

pp. 4054-4067

Author(s):

Steven Cunnington ◽

Stefano Camera ◽

Alkistis Pourtsidou

Keyword(s):

Nuisance Parameter ◽

Neutral Hydrogen ◽

Real Data ◽

Line Of Sight ◽

Markov Chain Analysis ◽

Significant Progress ◽

Intensity Mapping ◽

Chain Analysis ◽

Parallel Text ◽

Foreground Removal

ABSTRACT Potential evidence for primordial non-Gaussianity (PNG) is expected to lie in the largest scales mapped by cosmological surveys. Forthcoming 21 cm intensity mapping experiments will aim to probe these scales by surveying neutral hydrogen (H i) within galaxies. However, foreground signals dominate the 21 cm emission, meaning foreground cleaning is required to recover the cosmological signal. The effect this has is to damp the H i power spectrum on the largest scales, especially along the line of sight. Whilst there is agreement that this contamination is potentially problematic for probing PNG, it is yet to be fully explored and quantified. In this work, we carry out the first forecasts on fNL that incorporate simulated foreground maps that are removed using techniques employed in real data. Using an Monte Carlo Markov Chain analysis on an SKA1-MID-like survey, we demonstrate that foreground cleaned data recovers biased values [$f_{\rm NL}= -102.1_{-7.96}^{+8.39}$ (68 per cent CL)] on our fNL = 0 fiducial input. Introducing a model with fixed parameters for the foreground contamination allows us to recover unbiased results ($f_{\rm NL}= -2.94_{-11.9}^{+11.4}$). However, it is not clear that we will have sufficient understanding of foreground contamination to allow for such rigid models. Treating the main parameter $k_\parallel ^\text{FG}$ in our foreground model as a nuisance parameter and marginalizing over it, still recovers unbiased results but at the expense of larger errors ($f_{\rm NL}= 0.75^{+40.2}_{-44.5}$), which can only be reduced by imposing the Planck 2018 prior. Our results show that significant progress on understanding and controlling foreground removal effects is necessary for studying PNG with H i intensity mapping.

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On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽

10.3390/sym13081432 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1432

Author(s):

Dmitry O. Chernyshov ◽

Andrei E. Egorov ◽

Vladimir A. Dogiel ◽

Alexei V. Ivlev

Keyword(s):

Dark Matter ◽

Gamma Rays ◽

Molecular Clouds ◽

Alternative Explanation ◽

Gamma Ray ◽

Galactic Center ◽

The Self ◽

Large Area ◽

Mhd Turbulence ◽

The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

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Intensity mapping cross-correlations II: HI halo models including shot noise

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty3142 ◽

2018 ◽

Vol 484 (1) ◽

pp. 1007-1020 ◽

Cited By ~ 4

Author(s):

L Wolz ◽

S G Murray ◽

C Blake ◽

J S Wyithe

Keyword(s):

Shot Noise ◽

Intensity Mapping ◽

Cross Correlations

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DARK MATTER SEARCH WITH GAMMA RAYS: THE EXPERIMENTS EGRET AND GLAST

International Journal of Modern Physics A ◽

10.1142/s0217751x02011321 ◽

2002 ◽

Vol 17 (12n13) ◽

pp. 1829-1840 ◽

Cited By ~ 9

Author(s):

ALDO MORSELLI

Keyword(s):

Dark Matter ◽

Cosmic Rays ◽

Standard Model ◽

Supersymmetric Standard Model ◽

Minimal Supersymmetric Standard Model ◽

Gamma Rays ◽

Galactic Center ◽

Direct Detection ◽

Model Parameters ◽

Dark Matter Search

The direct detection of annihilation products in cosmic rays offers an alternative way to search for supersymmetric dark matter particles candidates. The study of the spectrum of gamma-rays, antiprotons and positrons offers good possibilities to perform this search in a significant portion of the Minimal Supersymmetric Standard Model parameters space. In particular the EGRET team have seen a convincing signal for a strong excess of emission from the galactic center that have not easily explanation with standard processes. We will review the achievable limits with the experiment GLAST taking into accounts the LEP results and we will compare this method with the antiproton and positrons experiments, the direct underground detection and with future experiments at LHC.

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