Foregrounds and Their Mitigation

Chapman, Emma; Jelić, Vibor

doi:10.1088/2514-3433/ab4a73ch6

Cited by 7 publications

(3 citation statements)

References 142 publications

(183 reference statements)

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“…However, the high-redshift Universe is notoriously difficult to observe. The high required sensitivity of galactic surveys [ 12 – 14 ], the presence of bright Galactic [ 15 , 16 ] and extragalactic [ 17 , 18 ] foregrounds in the radio sky (see [ 19 ] for a recent review) and systematics (e.g. [ 20 – 22 ]) prove to be a significant challenge.…”

Section: The Present-day Landscapementioning

confidence: 99%

Cosmic mysteries and the hydrogen 21-cm line: bridging the gap with lunar observations

Fialkov,

Gessey-Jones,

Dhandha

2024

Phil. Trans. R. Soc. A.

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The hydrogen 21-cm signal is predicted to be the richest probe of the young Universe, including those eras known as the cosmic Dark Ages, the Cosmic Dawn (when the first star and black hole formed) and the Epoch of Reionization. This signal holds the key to deciphering processes that take place at the early stages of cosmic history. In this opinion piece, we discuss the potential scientific merit of lunar observations of the 21-cm signal and their advantages over more affordable terrestrial efforts. The Moon is a prime location for radio cosmology which will enable precision observations of the low-frequency radio sky. The uniqueness of such observations is that they will provide an unparalleled opportunity to test cosmology and the nature of dark matter using the Dark Ages 21-cm signal. No less enticing is the opportunity to obtain a much clearer picture of the Cosmic Dawn than that currently achievable from the ground, which will allow us to determine the properties of the first stars and black holes. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades (part 2)’.

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Section: The Present-day Landscapementioning

confidence: 99%

Cosmic mysteries and the hydrogen 21-cm line: bridging the gap with lunar observations

Fialkov,

Gessey-Jones,

Dhandha

2024

Phil. Trans. R. Soc. A.

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“…The 21 cm line is more than 4 orders of magnitude fainter than the foregrounds such as synchrotron emission from galactic and extragalactic radio sources (e.g. Chapman & Jelić 2019). Thus, the detection of the 21 cm line is impossible without foreground mitigation techniques.…”

Section: Synergy With Other Experimentsmentioning

confidence: 99%

“…Foreground contamination is dominated by the synchrotron radiation from our Galaxy and extra-galactic radio sources such as AGNs (Jelić et al 2008;Chapman & Jelić 2019). Free-free emission is also a subdominant source of foregrounds.…”

Section: Foreground and Systematicsmentioning

confidence: 99%

Exploring the cosmic dawn and epoch of reionization with 21cm line

Shimabukuro,

Hasegawa,

Kuchinomachi

et al. 2023

Preprint

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The dark age of the universe, when no luminous object had existed, ended with the birth of the first stars, galaxies, and blackholes. This epoch is called cosmic dawn. Cosmic reionization is the major transition of the intergalactic medium (IGM) in the universe driven by ionizing photons emitted from luminous objects. Although the epoch through the dark age to reionization is a milestone in the universe, our knowledge of this epoch has not been sufficient yet. Cosmic 21cm signal, which is emitted from neutral hydrogen, is expected to open a new window for this epoch. In this review paper, we first introduce the basic physics of the 21cm line and how first stars impact on the 21cm line signal. Next, we briefly summarize how we extract astrophysical information from the 21cm line signal by means of statistical and machine learning approaches. We also discuss the synergy between the 21cm line signal and other emission lines. Finally, we summarize the current status of 21cm experiments.

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Using the sample variance of 21 cm maps as a tracer of the ionisation topology

Gorce

Hutter

Pritchard

2021

A&A

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Intensity mapping of the 21 cm signal of neutral hydrogen will yield exciting insights into the Epoch of Reionisation and the nature of the first galaxies. However, the large amount of data that will be generated by the next generation of radio telescopes, such as the Square Kilometre Array, as well as the numerous observational obstacles to overcome, require analysis techniques tuned to extract the reionisation history and morphology. In this context, we introduce a one-point statistic, which we refer to as the local variance, σloc, that describes the distribution of the mean differential 21 cm brightness temperatures measured in two-dimensional maps along the frequency direction of a light cone. The local variance takes advantage of what is usually considered an observational bias, the sample variance. We find the redshift-evolution of the local variance to not only probe the reionisation history of the observed patches of the sky, but also trace the ionisation morphology. This estimator provides a promising tool to constrain the midpoint of reionisation as well as gain insight into the ionising properties of early galaxies.

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Foregrounds and Their Mitigation

Cited by 7 publications

References 142 publications

Cosmic mysteries and the hydrogen 21-cm line: bridging the gap with lunar observations

Cosmic mysteries and the hydrogen 21-cm line: bridging the gap with lunar observations

Exploring the cosmic dawn and epoch of reionization with 21cm line

Using the sample variance of 21 cm maps as a tracer of the ionisation topology

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