21 cm cosmology in the 21st century

Pritchard, Jonathan R.; Loeb, Abraham

doi:10.1088/0034-4885/75/8/086901

Cited by 929 publications

(851 citation statements)

References 198 publications

(400 reference statements)

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“…Upcoming observations of the distribution of neutral hydrogen during reionization provides an indirect way to test the escape fractions and reionization sources that are favoured by our simulations (see e.g. Pritchard & Loeb 2012, for a review).…”

Section: Discussionmentioning

confidence: 99%

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

Paardekooper

Khochfar

Vecchia

2015

Monthly Notices of the Royal Astronomical Society

251

280

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Proto-galaxies forming in low-mass dark matter haloes are thought to provide the majority of ionizing photons needed to reionize the Universe, due to their high escape fractions of ionizing photons. We study how the escape fraction in high-redshift galaxies relates to the physical properties of the halo in which the galaxies form, by computing escape fractions in more than 75000 haloes between redshifts 27 and 6 that were extracted from the First Billion Years project, high-resolution cosmological hydrodynamics simulations of galaxy formation. We find that the main constraint on the escape fraction is the gas column density in a radius of 10 pc around the stellar populations, causing a strong mass dependence of the escape fraction. The lower potential well in haloes with M 200 10 8 M results in low column densities that can be penetrated by radiation from young stars (age < 5 Myr). In haloes with M 200 10 8 M supernova feedback is important, but only ∼ 30% of the haloes in this mass range have an escape fraction higher than 1%. We find a large range of escape fractions in haloes with similar properties, caused by different distributions of the dense gas in the halo. This makes it very hard to predict the escape fraction on the basis of halo properties and results in a highly anisotropic escape fraction. The strong mass dependence, the large spread and the large anisotropy of the escape fraction may strongly affect the topology of reionization and is something current models of cosmic reionization should strive to take into account.

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Section: Discussionmentioning

confidence: 99%

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

Paardekooper

Khochfar

Vecchia

2015

Monthly Notices of the Royal Astronomical Society

251

280

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“…Most baryonic matter in our Universe is in the form of Hydrogen, thus being able to emit and absorb in this line if neutral. Due to the large comoving volume, as well as the high resolution that can be achieved by observing this redshifted 21-cm line, there has been numerous studies into using it for cosmological measurements [43][44][45][46][47]. Of particular interest is the redshift range z = 30 − 100, also known as the "dark ages", where the 21-cm line can be observed in absorption against the CMB.…”

Section: -Cm Forecast For the Templatementioning

confidence: 99%

Prospects for cosmological collider physics

Meerburg

Münchmeyer

Muñoz

et al. 2017

J. Cosmol. Astropart. Phys.

110

120

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It is generally expected that heavy fields are present during inflation, which can leave their imprint in late-time cosmological observables. The main signature of these fields is a small amount of distinctly shaped non-Gaussianity, which if detected, would provide a wealth of information about the particle spectrum of the inflationary Universe. Here we investigate to what extent these signatures can be detected or constrained using futuristic 21-cm surveys. We construct model-independent templates that extract the squeezed-limit behavior of the bispectrum, and examine their overlap with standard inflationary shapes and secondary non-Gaussianities. We then use these templates to forecast detection thresholds for different masses and couplings using a 3D reconstruction of modes during the dark ages (z ∼ 30 − 100). We consider interactions of several broad classes of models and quantify their detectability as a function of the baseline of a dark ages interferometer. Our analysis shows that there exists the tantalizing possibility of discovering new particles with different masses and interactions with future 21-cm surveys. Contents

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“…This combination of effects implies that global 21-cm experiments should focus on the Lyα trough rather than on the reionization era. We also note that the redshift of the strongest absorption varies with the halo mass as it depends on the combined timing of the rise of Lyαcoupling and cosmic heating (see also Furlanetto, Oh & Briggs (2006) and Pritchard & Loeb (2012)). …”

Section: Global 21-cm Signalmentioning

confidence: 85%

The rich complexity of 21-cm fluctuations produced by the first stars

Fialkov

Barkana

2014

Monthly Notices of the Royal Astronomical Society

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We explore the complete history of the 21-cm signal in the redshift range z = 7 − 40. This redshift range includes various epochs of cosmic evolution related to primordial star formation, and should be accessible to existing or planned low-frequency radio telescopes. We use semi-numerical computational methods to explore the fluctuation signal over wavenumbers between 0.03 and 1 Mpc −1 , accounting for the inhomogeneous backgrounds of Lyα, X-ray, Lyman-Werner and ionizing radiation. We focus on the recently noted expectation of heating dominated by a hard X-ray spectrum from high-mass X-ray binaries. We study the resulting delayed cosmic heating and suppression of gas temperature fluctuations, allowing for large variations in the minimum halo mass that contributes to star formation. We show that the wavenumbers at which the heating peak is detected in observations should tell us about the characteristic mean free path and spectrum of the emitted photons, thus giving key clues as to the character of the sources that heated the primordial Universe. We also consider the line-of-sight anisotropy, which allows additional information to be extracted from the 21-cm signal. For example, the heating transition at which the cosmic gas is heated to the temperature of the cosmic microwave background should be clearly marked by an especially isotropic power spectrum. More generally, an additional cross-power component P X directly probes which sources dominate 21-cm fluctuations. In particular, during cosmic reionization (and after the just-mentioned heating transition), P X is negative on scales dominated by ionization fluctuations and positive on those dominated by temperature fluctuations.

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21 cm cosmology in the 21st century

Cited by 929 publications

References 198 publications

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

Prospects for cosmological collider physics

The rich complexity of 21-cm fluctuations produced by the first stars

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