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Effects of the sources of reionization on 21-cm redshift-space distortions
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Imperial College, UK.
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Uppsala University, Sweden.
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
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Number of Authors: 14
2016 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 456, no 2, 2080-2094 p.Article in journal (Refereed) Published
Abstract [en]

The observed 21 cm signal from the epoch of reionization will be distorted along the line of sight by the peculiar velocities of matter particles. These redshift-space distortions will affect the contrast in the signal and will also make it anisotropic. This anisotropy contains information about the cross-correlation between the matter density field and the neutral hydrogen field, and could thus potentially be used to extract information about the sources of reionization. In this paper, we study a collection of simulated reionization scenarios assuming different models for the sources of reionization. We show that the 21 cm anisotropy is best measured by the quadrupole moment of the power spectrum. We find that, unless the properties of the reionization sources are extreme in some way, the quadrupole moment evolves very predictably as a function of global neutral fraction. This predictability implies that redshift-space distortions are not a very sensitive tool for distinguishing between reionization sources. However, the quadrupole moment can be used as a model-independent probe for constraining the reionization history. We show that such measurements can be done to some extent by first-generation instruments such as LOFAR, while the SKA should be able to measure the reionization history using the quadrupole moment of the power spectrum to great accuracy.

Place, publisher, year, edition, pages
2016. Vol. 456, no 2, 2080-2094 p.
Keyword [en]
methods: numerical, dark ages, reionization, first stars
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-129640DOI: 10.1093/mnras/stv2812ISI: 000372264200068OAI: oai:DiVA.org:su-129640DiVA: diva2:924593
Available from: 2016-04-28 Created: 2016-04-26 Last updated: 2016-05-18Bibliographically approved
In thesis
1. Simulating observational probes of reionization
Open this publication in new window or tab >>Simulating observational probes of reionization
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The time in the history of the Universe when the first stars and galaxies formed and ionized the gas in the intergalactic medium is known as the Epoch of Reionization. This transformative time period, which took place within the first billion years after the Big Bang, is still relatively unexplored due to the significant difficulties associated with observing so far back in time. The theme of this thesis is tying together existing (mostly indirect) and upcoming observations with simulations.

Papers I and II deal with Lyα emitting galaxies. The Lyα emission line is very sensitive to neutral hydrogen, which was plentiful during the Epoch of Reionization. Therefore, observations of distant Lyα galaxies may be used to indirectly tell us something about when and how reionization took place. Properly interpreting the observations is, however, far from straightforward. In Paper I we develop a new method for combining large, low-resolution simulations of the intergalactic medium with small, high-resolution simulations of individual galaxies. We use this method to reproduce existing observations. In Paper II we use the same method to make predictions for future observations.

Another observational probe of the EoR is the 21-cm emission line from neutral hydrogen. This line is the most promising probe for directly studying the neutral gas in the early Universe, and several radio telescopes are currently gathering data to observe it. The 21-cm signal is affected by a multitude of cosmological and astrophysical effects, all of which need to be understood in order to interpret the upcoming observations. One such effect is the non-random shifts in redshifts caused by the peculiar velocity of matter flowing towards higher-density regions. This effect, known as redshift space distortions, is the topic of papers III and IV, while paper V deals with another observational effect called the lightcone effect. 

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2015. 54 p.
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-115728 (URN)978-91-7649-143-0 (ISBN)
Public defence
2015-05-29, sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

Available from: 2015-05-07 Created: 2015-03-30 Last updated: 2016-05-18Bibliographically approved

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Mellema, GarreltLee, Kai-Yan
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