Understanding The Epoch Of Cosmic Reionization

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Understanding The Epoch Of Cosmic Reionization

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Author : Andrei Mesinger
language : en
Publisher: Springer
Release Date : 2015-11-28

Understanding The Epoch Of Cosmic Reionization written by Andrei Mesinger and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-11-28 with Science categories.

The dawn of the first stars, galaxies and black holes signaled a fundamental milestone in our Universe’s evolution: the Epoch of Reionization. The light from these galactic ancestors began spreading out, ionizing virtually every atom in existence. Our Universe transitioned from darkness to light, from cold to hot, from simple and boring to the wondrous cosmic zoo we see around us today. Despite its importance, observations of reionization have been few, and their interpretation has been highly controversial. Fortunately, this is rapidly changing. We will soon enter the "Big Data” era of this mysterious epoch, driven by an upcoming wave of observations with state-of-the-art telescopes as well as new sophisticated analysis tools. The aim of this volume is to summarize the current status and future outlook of the reionization field. We bring together leading experts in many sub-disciplines, highlighting the measurements that will illuminate our understanding of reionization and the cosmic dawn: (i) 21cm interferometry; (ii) high-redshift quasar spectra; (iii) high-redshift galaxy surveys; (iv) primary and secondary anisotropies of the Cosmic Microwave Background; (v) high-resolution studies of the metal content of early galaxies. We seek a roadmap to interpreting the wealth of upcoming observations. What is the best use of limited observational resources? How do we develop theoretical tools tailored for each observation? Ultimately, what will we learn about the epoch of reionization and our galactic ancestors?

Using Galaxy Clusters As Cosmic Telescopes To Probe The Epoch Of Reionization

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Author : Austin Thomas Hoag
language : en
Publisher:
Release Date : 2018

Using Galaxy Clusters As Cosmic Telescopes To Probe The Epoch Of Reionization written by Austin Thomas Hoag and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.

The Epoch of Reionization (hereafter "cosmic reionization" or simply "reionization") is one of the most significant remaining puzzles in cosmic history. Occurring less than one billion years after the Big Bang, reionization likely took place shortly after the formation of the first baryonic structures such as stars, galaxies and active galactic nuclei (AGN). Reionization is therefore intimately linked to several core astronomical fields such as: stellar formation and evolution, galaxy formation and evolution, large scale structure, and the cosmic microwave background, to name a few. In the last decade, significant investments have been made to observe galaxies during reionization, for example in the optical and near infrared with the Hubble Ultra-Deep Field, the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey, and the Hubble Frontier Fields. Experiments at radio frequencies have recently been undertaken to detect the global 21 cm signal expected from reionization, for example the Experiment to Detect the Global Epoch of reionization Signature, as well as to measure the power spectrum of the 21 cm radiation, such as the Murchison Wide Field Array and the Low-Frequency Array. While reionization has been a major focus in astronomy for over a decade, many key properties of the process are still uncertain. The main difficulty in constraining reionization is the faintness of the sources likely driving it, i.e. the first galaxies and AGN. Even with the most powerful current telescopes such as Keck and the Hubble Space Telescope (HST), observing all but the brightest of these sources is too expensive. Using a galaxy cluster as a gravitational lens, this observational challenge can be somewhat eased. In order to take advantage of cluster lensing to study faint galaxies, a gravitational lens model is required. In this dissertation, I present gravitational lens models I developed for 11 galaxy clusters in three large cluster surveys undertaken with the Hubble Space Telescope and the Spitzer Space Telescope. I selected redshift (z) 7 to 8 galaxies behind all of these clusters and followed them up with the Multi-Object Spectrometer For InfraRed Exploration (MOSFIRE) on the Keck I telescope. During this spectroscopic campaign I discovered a Lyman-alpha emitting galaxy at z=7.64 magnified by a factor of approximately 10. Its intrinsic luminosity is an order of magnitude fainter than the handful of other known Lyman-alpha emitters (LAEs) at z>7.5, all of which are bright, rare sources. While exhibiting weaker Lyman-alpha than the UV-brighter LAEs at z>7.5, the underlying mechanism which allows Lyman-alpha to escape all of these galaxies may be the same. I also obtained the tightest spectroscopic constraints on the redshift of one of the highest redshift gravitationally lensed galaxies (z~9) using ultra-deep grism spectroscopy from the Hubble Space Telescope. Using a sub-sample consisting of 8 out of 11 of these clusters for which the photometric analysis is complete, I constrained the fraction of Lyman-break galaxies showing Lyman-alpha, often just called the "Lyman-alpha fraction test," at z=8, making the first definitive measurement of a declining Lyman-alpha fraction (and hence increasing neutral hydrogen fraction) over the interval z=7-8 for UV-fainter galaxies. This is the first hint that faint galaxies suffer a similarly large decline in Lyman-alpha fraction as bright galaxies over this interval, suggesting that the overlap phase of reionization may still be underway at z=8.

A Multiwavelength Study Of The Epoch Of Reionization Through Intensity Fluctuations

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Author : Ketron Mitchell-Wynne
language : en
Publisher:
Release Date : 2016

A Multiwavelength Study Of The Epoch Of Reionization Through Intensity Fluctuations written by Ketron Mitchell-Wynne and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.

The diffuse cosmological background light that pervades our Universe continues to be one of the best probes to uncover the astrophysical environments of the early Universe. In our attempt to gain a more holistic understanding of our present cosmological situation, we seek to understand the formation and evolution of the first stars and galaxies that came into existence. It is thought that these first-light galaxies are the progenitors to our Milky Way, and all other evolved galaxies. The spatial fluctuations of the extragalactic background light trace the total emission from all stars and galaxies in the Universe, and these first-light galaxies have left a measurable imprint on the cosmic infrared backgroud (CIB) light. In the first part of this thesis I describe measurements which suggest a detection of this signal, using a large subset of data from the largest allocation of Hubble time to date (CANDELS). This is followed by a cross-correlation analysis of the CIB with the cosmic X-ray background (CXB), which can give some insight as to whether or not X-ray emitting sources were present during this first-light epoch. I then shift towards the far-infrared (submillimeter) regime and discuss a statistical measurement of the redshift distribution of Herschel galaxies. Finally I show two-point correlation measurements of strongly lensed submillimeter galaxies, and the bias that this population may be introducing into past and current clustering analyses, which can lead to erroneous dark matter halo mass measurements from such studies.

Techniques For The Analysis And Understanding Of Cosmic Evolution

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Author : Matthew John Kolopanis
language : en
Publisher:
Release Date : 2018

Techniques For The Analysis And Understanding Of Cosmic Evolution written by Matthew John Kolopanis and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with Cosmic background radiation categories.

The Cosmic Microwave Background (CMB) has provided precise information on the evolution of the Universe and the current cosmological paradigm. The CMB has not yet provided definitive information on the origin and strength of any primordial magnetic fields or how they affect the presence of magnetic fields observed throughout the cosmos. This work outlines an alternative method to investigating and identifying the presence of cosmic magnetic fields. This method searches for Faraday Rotation (FR) and specifically uses polarized CMB photons as back-light. I find that current generation CMB experiments may be not sensitive enough to detect FR but next generation experiments should be able to make highly significant detections. Identifying FR with the CMB will provide information on the component of magnetic fields along the line of sight of observation. The 21cm emission from the hyperfine splitting of neutral hydrogen in the early universe is predicted to provide precise information about the formation and evolution of cosmic structure, complementing the wealth of knowledge gained from the CMB. 21cm cosmology is a relatively new field, and precise measurements of the Epoch of Reionization (EoR) have not yet been achieved. In this work

Advancing Astrophysics With The Square Kilometre Array Proceedings From A Meeting Held In Giardini Naxos Sicily Italy 9 13 June 2014

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Author :
language : en
Publisher:
Release Date : 2015

Advancing Astrophysics With The Square Kilometre Array Proceedings From A Meeting Held In Giardini Naxos Sicily Italy 9 13 June 2014 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with Astronomy categories.

Simulations Of Cosmic Reionization

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Author : Milan Raicevic
language : en
Publisher:
Release Date : 2010

Simulations Of Cosmic Reionization written by Milan Raicevic and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Radiative transfer categories.

In this thesis we investigate numerically how ionizing photons emitted by stars in galaxies cause the reionization of the Universe, the transition during which most of the gas in the Universe from a mostly neutral, to a highly ionised state it is in today. To this end, we discuss and improve two techniques for the transport of ionising radiation across cosmological volumes, analyse the sources of ionising photons at high redshifts predicted by a semi-analytical galaxy formation model (GALFORM), and combine these to make consistent model of how reionization proceeds. Our improvements to the hybrid characteristics (HC) radiative transport scheme are significant, making the code faster and more accurate, as demonstrated by our contribution to a code comparison paper (Iliev et al., 2009). Our improvements to the SimpleX radiative transport scheme allow for accurate and significantly better numerically converged calculations of the speeds of ionization fronts of cosmological HII regions. This is accomplished by a much more thorough analysis of how to properly model the density?eld on the unstructured density?eld in SimpleX. The dependence of the ionizing emissivity of GALFORM galaxies on various parameters of the model is examined. We show that massive stars formed in abundance because of the assumed top-heavy stellar initial mass function during starbursts in the Baugh et al. (2005) model, triggered by galaxy mergers, are the dominant source of ionizing photons. We show that the luminosity functions predicted by this model are in good agreement with the most recent Hubble Space Telescope results at z \gtrsim 8. The model also demonstrates that most photons are produced in faint galaxies which are not yet seen in the current data. We then combine the sources predicted by GALFORM with the SimpleX RT scheme to model inhomogeneous reionization including the effects of source suppression. We investigate how the morphology of reionization depends on the model for the sources, which may be crucial for future observations of this cosmic epoch.

The Kinetic Sunyaev Zel Dovich Effect As A Probe Of The Physics Of Cosmic Reionization

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Author : Hyunbae Park
language : en
Publisher:
Release Date : 2015

The Kinetic Sunyaev Zel Dovich Effect As A Probe Of The Physics Of Cosmic Reionization written by Hyunbae Park and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.

We calculate the angular power spectrum of the cosmic microwave background temperature fluctuations induced by the kinetic Sunyaev-Zel'dovich (kSZ) effect from the epoch of reionization (EOR). We use detailed N-body+radiative-transfer simulations to follow inhomogeneous reionization of the intergalactic medium. For the first time, we take into account the "self-regulation" of reionization: star formation in low-mass dwarf galaxies or minihalos is suppressed if these halos form in the regions that were already ionized or Lyman-Werner dissociated. Some previous work suggested that the amplitude of the kSZ power spectrum from the EOR can be described by a two-parameter family: the epoch of half-ionization and the duration of reionization. However, we argue that this picture applies only to simple forms of the reionization history which are roughly symmetric about the half-ionization epoch. In self-regulated reionization, the universe begins to be ionized early, maintains a low level of ionization for an extended period, and then finishes reionization as soon as high-mass atomically cooling halos dominate. While inclusion of self-regulation affects the amplitude of the kSZ power spectrum only modestly (~10%), it can change the duration of reionization by a factor of more than two. We conclude that the simple two-parameter family does not capture the effect of a physical, yet complex, reionization history caused by self-regulation. When added to the post-reionization kSZ contribution, our prediction for the total kSZ power spectrum is below the current upper bound from the South Pole Telescope. Therefore, the current upper bound on the kSZ effect from the EOR is consistent with our understanding of the physics of reionization.

On The Evolution Of Galaxy Protoclusters From The Epoch Of Reionization To Cosmic Noon

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Author : Jaclyn Bradli Champagne
language : en
Publisher:
Release Date : 2022

On The Evolution Of Galaxy Protoclusters From The Epoch Of Reionization To Cosmic Noon written by Jaclyn Bradli Champagne and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.

Over the last 7–8 billion years, mature galaxy clusters, characterized by massive quiescent galaxy populations residing in > 1014 M [subscript ☉] dark matter halos, have become ubiquitous features of the cosmic web. It is theorized that these clusters are preceded by a proto-cluster stage, which form at much earlier times in filamentary dark matter overdensities and later collapse into a central dark matter halo. Identifying and characterizing protoclusters between the epoch of reionization and cosmic noon, during which time they are expected to undergo periods of rapid star formation and evolution prior to gravitational collapse, remains in its nascent stages. With a heterogeneous mix of selection techniques, spectroscopic completeness, area coverage, and wavelength coverage, we are still vitally lacking a statistically complete catalog of protoclusters — and even more so a general understanding of their physical properties. This doctoral thesis addresses these questions twofold by: 1) using z ∼ 6 quasars as tracers of overdensities at multiple wavelengths, and 2) presenting a comprehensive X-ray to radio case study of a massive protocluster at z = 2.5. The first half of this thesis focuses on understanding the environments of the brightest quasars at z > 6, under the hypothesis that quasars hosting > 109 M [subscript ☉] black holes signal regions of accelerated growth and mass buildup in the early Universe. In two separate studies, I present the results of searches for enhanced star formation in the vicinities of quasars, using two complementary tracers of star–forming galaxies. Using data from the Atacama Large Millimeter Array, I show that a search for extreme dust–obscured galaxies via millimeter continuum emission yields inconclusive results concerning our ability to detect a true overdensity signal. Using the Hubble Space Telescope to search for the more abundant and less massive population of Lyman break galaxies, I show a heterogeneity of overdensity signals near these quasars. The second half of this thesis focuses on multiwavelength observations of known protoclusters at lower redshifts, where more observational tools are available to constrain their environments. I present an analysis of the member galaxies within a structurally complex protocluster core at z = 2.5 located in the COSMOS extragalactic field, using data from the Atacama Large Millimeter Array, the Very Large Array, and the COSMOS archive. I evaluate possible evolutionary hypotheses on the basis of the morphology of the cold gas needed for future star formation, the spatial distribution of its member galaxies, and the existence of a marginal X-ray detection that all present a challenge to our cosmological understanding of virial collapse of clusters during this epoch. Finally, I present a future outlook on further case studies and large surveys which will be made possible by next generation facilities

Fundamentals Of Cosmology

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Author : James Rich
language : en
Publisher: Springer Science & Business Media
Release Date : 2009-12-03

Fundamentals Of Cosmology written by James Rich and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009-12-03 with Science categories.

A self-contained introduction to general relativity that is based on the homogeneity and isotropy of the local universe. Emphasis is placed on estimations of the densities of matter and vacuum energy, and on investigations of the primordial density fluctuations and the nature of dark matter.

The Effects Of Dark Matter Annihilation On Cosmic Reionization

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Author :
language : en
Publisher:
Release Date : 2015

The Effects Of Dark Matter Annihilation On Cosmic Reionization written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.

We revisit the possibility of constraining the properties of dark matter (DM) by studying the epoch of cosmic reionization. Previous studies have shown that DM annihilation was unlikely to have provided a large fraction of the photons that ionized the universe, but instead played a subdominant role relative to stars and quasars. The DM, however, begins to efficiently annihilate with the formation of primordial microhalos at $z\sim100-200$, much earlier than the formation of the first stars. Therefore, if DM annihilation ionized the universe at even the percent level over the interval $z \sim 20-100$, it can leave a significant imprint on the global optical depth, $\tau$. Moreover, we show that cosmic microwave background (CMB) polarization data and future 21 cm measurements will enable us to more directly probe the DM contribution to the optical depth. In order to compute the annihilation rate throughout the epoch of reionization, we adopt the latest results from structure formation studies and explore the impact of various free parameters on our results. We show that future measurements could make it possible to place constraints on the dark matter's annihilation cross section that are at a level comparable to those obtained from the observations of dwarf galaxies, cosmic ray measurements, and studies of recombination.