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High Redshift Galaxies as Probes of the Epoch of Reionization

2016
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Release : 2016
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Book Synopsis High Redshift Galaxies as Probes of the Epoch of Reionization by : Jessie Frances Taylor

Download or read book High Redshift Galaxies as Probes of the Epoch of Reionization written by Jessie Frances Taylor. This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: Following the Big Bang, as the Universe cooled, hydrogen and helium recombined, forming neutral gas. Currently, this gas largely resides between galaxies in a highly diffuse state known as the intergalactic medium (IGM). Observations indicate that the IGM, fueled by early galaxies and/or accreting black holes, "reionized" early in cosmic history--the entire volume of the Universe refilling with ionized gas. This thesis analyzes and develops several ways to use observations of high redshift galaxies to probe this period, the Epoch of Reionization (EoR). We examine the redshift evolution of the Ly[alpha] fraction, the percentage of Lyman-break selected galaxies (LBGs) that are Lyman-[alpha] emitting galaxies (LAEs). Observing a sharp drop in this fraction at z~7, many early studies surmised the z~7 IGM must be surprisingly neutral. We model the effect of patchy reionization on Ly[alpha] fraction observations, concluding that sample variance reduces the neutral fraction required. We quantify the prospects for measuring the enhanced spatial clustering of LAEs due to reionization with upcoming observations from the Hyper Suprime Cam. LBGs from that survey provide a useful comparison sample. We consider the effect of foreground "interlopers" on the clustering signal. We conclude that if HSC observes back into the EoR, the abundance and spatial clustering of galaxies and the size distribution of void regions evolve more strongly with redshift for LAEs than LBGs. Moreover, measuring the cross-power spectrum between LAEs and LBGs reduces the interloper effect.We examine line intensity mapping experiments which trace large scale structure by measuring spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. We develop a technique to separate "interloper" emissions, which these surveys are vulnerable to, at the power spectrum level, based on distortions introduced when the interloper emissions are (incorrectly) assumed to originate from the target redshift. Applying this to a hypothetical [CII] emission survey at z~7, we find the distinctive interloper anisotropy can be used to separate strong foreground CO emission fluctuations.

Understanding the Epoch of Cosmic Reionization

2015-11-28 Science
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Release : 2015-11-28
Genre : Science
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Book Synopsis Understanding the Epoch of Cosmic Reionization by : Andrei Mesinger

Download or read book Understanding the Epoch of Cosmic Reionization written by Andrei Mesinger. This book was released on 2015-11-28. Available in PDF, EPUB and Kindle. Book excerpt: 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?

Unveiling the Epoch of Reionization by Simulations and High-redshift Galaxies

2014
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Release : 2014
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Book Synopsis Unveiling the Epoch of Reionization by Simulations and High-redshift Galaxies by :

Download or read book Unveiling the Epoch of Reionization by Simulations and High-redshift Galaxies written by . This book was released on 2014. Available in PDF, EPUB and Kindle. Book excerpt: The Epoch of Reionization marks after recombination the second major change in the ionization state of the universe, going from a neutral to an ionized state. It starts with the appearance of the first stars and galaxies; a fraction of high-energy photons emitted from galaxies permeate into the intergalactic medium (IGM) and gradually ionize the hydrogen, until the IGM is completely ionized at z~6 (Fan et al., 2006). While the progress of reionization is driven by galaxy evolution, it changes the ionization and thermal state of the IGM substantially and affects subsequent structure and galaxy formation by various feedback mechanisms. Understanding this interaction between reionization and galaxy formation is further impeded by a lack of understanding of the high-redshift galactic properties such as the dust distribution and the escape fraction of ionizing photons. Lyman Alpha Emitters (LAEs) represent a sample of high-redshift galaxies that are sensitive to all these galactic properties and the effects of reionization. In this the...

Galaxies at the Epoch of Reionization

2018
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Release : 2018
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Book Synopsis Galaxies at the Epoch of Reionization by : Charlotte Mason

Download or read book Galaxies at the Epoch of Reionization written by Charlotte Mason. This book was released on 2018. Available in PDF, EPUB and Kindle. Book excerpt: The reionization of intergalactic hydrogen in the universe's first billion years was likely driven by the first stars and galaxies, so its history encodes information about their prop- erties. But the timeline of reionization is not well-measured and it is still unclear whether galaxies alone can produce the required ionizing photons. In my thesis I have focused on two ways to use galaxies at our current observational frontiers to constrain reionization and high redshift galaxy evolution. One tool is the UV luminosity function (LF), which traces the evolution of star-forming galaxies and their ionizing photons. Accurately measuring LFs and understanding their evolution are important for understanding the connections between galaxies and their dark matter halos. I developed a simple, but powerful, semi-analytic model for LF evolution assuming star formation is driven by dark matter accretion. This has proved remarkably consistent with observations, and implies the majority of star formation at high redshifts occurs in low mass galaxies. I also developed a technique to improve the accuracy of LF by accounting for gravitational lensing magnification bias. Secondly, Lyman alpha (Ly ) emission from galaxies can probe the intergalactic medium (IGM) ionization state as Ly photons are strongly attenuated by neutral hydrogen, but this requires disentangling physics on pc to Gpc scales. I developed a new forward-modeling Bayesian framework combining cosmological IGM simulations with interstellar medium models to infer the IGM neutral hydrogen fraction from observations of Ly emission. My thesis presents new measurements of the neutral fraction at z 7 and z 8, which, along with other independent constraints, provide increasing evidence for the bulk of reionization occurring at z 6 8. This is consistent with reionization being driven by ultra-faint galaxies with a low average ionizing photon escape fraction. We also show that reionization impacts Ly emission from different galaxy populations in different ways: UV bright galaxies living in overdense regions that reionize early have potentially visible Ly even in a highly neutral IGM. The upcoming James Webb Space Telescope was designed to observe galaxies at Cosmic Dawn. Throughout this thesis I have made predictions for what JWST may observe in the context of high redshift galaxy evolution.

Lyman Alpha Emitting Galaxies at High Redshift

2005 Science
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Release : 2005
Genre : Science
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Book Rating : 942/5 ( reviews)

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Book Synopsis Lyman Alpha Emitting Galaxies at High Redshift by : Steven Arthur Dawson

Download or read book Lyman Alpha Emitting Galaxies at High Redshift written by Steven Arthur Dawson. This book was released on 2005. Available in PDF, EPUB and Kindle. Book excerpt: As late as 1995, the anticipated widespread population of primeval galaxies remained at large, lurking undetected at unknown redshifts, with undiscovered properties. We present results from our efforts to detect and characterize primeval galaxies by their signature high-redshift Lyman-alpha emission lines utilizing two observational techniques: serendipitous slit spectroscopy and narrowband imaging. By pushing these techniques to their utmost limits, we probe the Lyman-alpha-emitting galaxy population out to redshifts as high as z = 6.5. Galaxies at this epoch reside in a universe which is just 800 million years old, a mere 6% of its current age. As such, this work provides one account of the manner by which observational cosmology has recently shifted from merely marveling at the incredible lookback times implied by the first few high-redshift detections, to the routine assembly of high-redshift datasets designed to address specific astrophysical issues.

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