Observations of Strong Emission Line Galaxies from the Epoch of Reionization to Present Day

2023

Author : Anthony Joseph Taylor
Release : 2023
Genre :
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Book Synopsis Observations of Strong Emission Line Galaxies from the Epoch of Reionization to Present Day by : Anthony Joseph Taylor

Download or read book Observations of Strong Emission Line Galaxies from the Epoch of Reionization to Present Day written by Anthony Joseph Taylor. This book was released on 2023. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a search for Ultra-Luminous Lyman Alpha Emitters (ULLAEs) in the Epoch of Reionization (EoR) using a combination of wide-field narrowband imaging and focused spectroscopic follow-up. ULLAEs are the brightest known Lyman-alpha (LyÎł) emitting galaxies, and are a unique probe of the evolution of galaxies and their environments in the EoR. I use the HEROES dataset-a contiguous 45 sq. degree grizY broadband and NB816+NB921 narrowband survey in the North Ecliptic Pole-to search for these objects. I describe a re-reduction of the HEROES dataset that increased its imaging depth, expanded its multiband sky coverage, and eliminated data corruption and artifacts. Using HEROES, I identify narrowband excess and Lyman break selected ULLAE candidates and confirm them spectroscopically with Keck/DEIMOS. I use the resulting spectroscopic populations to construct LyÎł luminosity functions at redshifts z = 5.7 and z = 6.6 in order to test the theory that ULLAEs can produce large ionized bubbles around themselves in the late EoR. The results indicate an overdensity of ULLAEs at z = 6.6, likely caused by increased LyÎł escape resulting from self-supported ionized bubbles around the ULLAEs. Finally, I use JWST NIRSpec Early Research Observations of the lensing cluster SMACS J0723.3-7327 to calculate Direct Te metallicities for five galaxies at z > 5. This dissertation contributes to a better understanding of the properties and environments of ULLAEs during and near the EoR, introduces the HEROES dataset, and offers a preview of JWST's capabilities for EoR science.

Luminosity Function of Lyman-alpha Emitters at the Reionization Epoch

2011 Galaxies

Author : Vithal Shet Tilvi
Release : 2011
Genre : Galaxies
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Book Synopsis Luminosity Function of Lyman-alpha Emitters at the Reionization Epoch by : Vithal Shet Tilvi

Download or read book Luminosity Function of Lyman-alpha Emitters at the Reionization Epoch written by Vithal Shet Tilvi. This book was released on 2011. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies with strong Lyman-alpha (Lya) emission line (also called Lya galaxies or emitters) offer an unique probe of the epoch of reionization - one of the important phases when most of the neutral hydrogen in the universe was ionized. In addition, Lya galaxies at high redshifts are a powerful tool to study low-mass galaxy formation. Since current observations suggest that the reionization is complete by redshift z~ 6, it is therefore necessary to discover galaxies at z> 6, to use their luminosity function (LF) as a probe of reionization. I found five z = 7.7 candidate Lya galaxies with line fluxes> 7x10-18 cm/2, from three different deep near-infrared (IR) narrowband (NB) imaging surveys in a volume> 4x104Mpc3. From the spectroscopic followup of four candidate galaxies, and with the current spectroscopic sensitivity, the detection of only the brightest candidate galaxy can be ruled out at 5 sigma level. Moreover, these observations successfully demonstrate that the sensitivity necessary for both, the NB imaging as well as the spectroscopic followup of z~ 8 Lya galaxies can be reached with the current instrumentation. While future, more sensitive spectroscopic observations are necessary, the observed Lya LF at z = 7.7 is consistent with z = 6.6 LF, suggesting that the intergalactic medium (IGM) is relatively ionized even at z = 7.7, with neutral fraction xHI 30%. On the theoretical front, while several models of Lya emitters have been developed, the physical nature of Lya emitters is not yet completely known. Moreover, multi-parameter models and their complexities necessitates a simpler model. I have developed a simple, single-parameter model to populate dark mater halos with Lya emitters. The central tenet of this model, different from many of the earlier models, is that the star-formation rate (SFR), and hence the Lya luminosity, is proportional to the mass accretion rate rather than the total halo mass. This simple model is successful in reproducing many observable including LFs, stellar masses, SFRs, and clustering of Lya emitters from z~ 3 to z~ 7. Finally, using this model, I find that the mass accretion, and hence the star-formation in> 30% of Lya emitters at z~ 3 occur through major mergers, and this fraction increases to ~ 50% at z~7.

High Redshift Galaxies as Probes of the Epoch of Reionization

2016

Author : Jessie Frances Taylor
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.

How Did the First Stars and Galaxies Form?

2010-07-19 Science

Author : Abraham Loeb
Release : 2010-07-19
Genre : Science
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Book Rating : 066/5 ( reviews)

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Book Synopsis How Did the First Stars and Galaxies Form? by : Abraham Loeb

Download or read book How Did the First Stars and Galaxies Form? written by Abraham Loeb. This book was released on 2010-07-19. Available in PDF, EPUB and Kindle. Book excerpt: A concise introduction to cosmology and how light first emerged in the universe Though astrophysicists have developed a theoretical framework for understanding how the first stars and galaxies formed, only now are we able to begin testing those theories with actual observations of the very distant, early universe. We are entering a new and exciting era of discovery that will advance the frontiers of knowledge, and this book couldn't be more timely. It covers all the basic concepts in cosmology, drawing on insights from an astronomer who has pioneered much of this research over the past two decades. Abraham Loeb starts from first principles, tracing the theoretical foundations of cosmology and carefully explaining the physics behind them. Topics include the gravitational growth of perturbations in an expanding universe, the abundance and properties of dark matter halos and galaxies, reionization, the observational methods used to detect the earliest galaxies and probe the diffuse gas between them—and much more. Cosmology seeks to solve the fundamental mystery of our cosmic origins. This book offers a succinct and accessible primer at a time when breathtaking technological advances promise a wealth of new observational data on the first stars and galaxies. Provides a concise introduction to cosmology Covers all the basic concepts Gives an overview of the gravitational growth of perturbations in an expanding universe Explains the process of reionization Describes the observational methods used to detect the earliest galaxies

The First Galaxies

2012-12-15 Science

Author : Tommy Wiklind
Release : 2012-12-15
Genre : Science
Kind : eBook
Book Rating : 626/5 ( reviews)

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Book Synopsis The First Galaxies by : Tommy Wiklind

Download or read book The First Galaxies written by Tommy Wiklind. This book was released on 2012-12-15. Available in PDF, EPUB and Kindle. Book excerpt: New observations of the period between the cosmic recombination and the end of reionization are posing intriguing questions about where the first generations of stars were formed, how the first galaxies were assembled, whether these galaxies have low redshift counterparts, and what role the early galaxies played in the reionization process. Combining the new observational data with theoretical models can shed new light on open issues regarding the star formation process, its role in the reionization of the Universe, and the metal enrichment in galaxies at those early epochs. This volume brings together leading experts in the field to discuss our current level of understanding and what may come in the near future as our observational as well as theoretical tools improve. The book confronts the theory of how the first stars, black holes, and galaxies formed with current and planned observations. This synthesis is very timely, just ahead of the establishment of major new facilities, such as the James Webb Space Telescope (JWST), a next-generation, millimeter/sub-millimeter observatory in the Atacama desert (ALMA), and ground-based Extremely Large Telescopes (ELT). Together, they will revolutionize the study of the most distant objects in the Universe. This volume is aimed at beginning graduate students but can also serve as a reference work for active researchers in the field. Apart from presenting the fundamental concepts involved, it also provides an introduction to the methods and techniques used. The book will also be useful to anyone with an astrophysical background who needs an effective starting point for learning about the first stars and galaxies.

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