Lyman Alpha Emitting Galaxies at High Redshift PDF Download

Author: Steven Arthur Dawson
Publisher: Universal-Publishers
ISBN: 1581122942
Category : Science
Languages : en
Pages : 203

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Book Description
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.

Author: Kamson Yeuk Yu Lai
Publisher:
ISBN:
Category :
Languages : en
Pages : 314

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This thesis presents studies on Ly[alpha] emitting galaxies (LAEs) at high redshift. The main goal of this work is to understand the nature and evolution of LAEs, with the broader aim of gaining insights into galaxy formation and evolution in general. We achieve the stated goal by constraining the stellar populations of LAEs at z ~ 3 - 6 using detailed multiwavelength observations. Using deep Spitzer IRAC imaging, we study the stellar populations of LAEs at z = 5.7 and 6.6. IRAC observations sample the rest-frame optical emission from the z ~ 6 LAEs, thus allowing the stellar masses and star formation histories of the galaxies to be constrained. Interestingly, we find that IRAC-detected LAEs at z ~ 6 can be massive and evolved, unlike typical LAEs at lower redshifts. Extending our work to lower redshift, we study the overall properties of LAEs at z = 3.1 using a large sample of 162 objects. The majority of the LAEs in our sample are young and low-mass galaxies but there is also a significant fraction of older and more massive objects. The fact that Ly[alpha] emission can be seen in both young and evolved galaxies has interesting implications for the evolution of LAEs. In a further study, we use a combined sample of 40 spectroscopically selected and 111 photometrically selected objects to constrain the average stellar population of LAEs at z = 5.7. Surprisingly, the z = 5.7 LAEs in our sample appear to be more massive on average than their low-redshift counterparts. Additionally, we demonstrate that at higher redshift LAEs account for a larger fraction of the global stellar mass density and star formation rate density. Our results suggest a possible evolution of LAEs towards higher mass with redshift, potentially due to the increasing prevalence of Ly[alpha] emission as a result of the lower overall dust content in high-redshift galaxies.

Author: Spencer Fuller
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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We present 36 spectroscopically confirmed Lyman-alpha emitting galaxies (LAEs) from follow-up observations with Keck/DEIMOS of high-redshift candidates behind 10 galaxy cluster lenses. High-redshift candidates were selected to be between 5 [less than or approximately equal to] z [less than or approximately equal to 7] from a variety of photometric data using HST and Spitzer imaging surveys including the Cluster Lensing And Supernova Survey with Hubble (CLASH), the Hubble Frontier Fields (HFF), and the Spitzer UltRa Faint SUrvey Program (SURFSUP). A subset of 27 of our targets were prioritized from the Grism Lens-Amplified Survey from Space (GLASS). After compiling a large sample of potential high-redshift candidates from our extensive spectroscopic program, we used photometric redshift information derived from accompanying photometric data to perform an integrated P(z) cut >1% between 5 z 7 in order to construct a sample of 198 high-redshift objects, 136 primary targets and 62 secondaries (serendipitous objects). Our high-redshift sample spans intrinsic UV luminosities from a few L* down to 0.001L* (where L* is the characteristic luminosity of galaxies in our redshift range). We identified 19 high-confidence detections of Ly[alpha] in our final sample and an additional 17 likely detections. Five of these detections have been previously reported spectroscopically. We divided our sample into a lower-redshift (z [approximately equal to] 5.5) and higher-redshift (z [approximately equal to] 6.5) sample and ran Monte Carlo trials, incorporating the strength of the Ly[alpha]emission, the photometric redshift of the non-detections, and different treatments of multiple images. Considering only objects where Ly[alpha]could be detected at EW(Ly[alpha])25Å at 3[sigma] at the fiducial depth of our survey, and considering only those galaxies with EW(Ly[alpha])25Å as true LAEs, and finally, considering only objects with m[subscript AB]

Author: Milan Bogosavljević
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 324

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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And with model predictions, indicates that bright Ly-alpha galaxies are so rare beyond z=5 that a non-evolving population can be excluded.

Author: Richard Waller Hunstead
Publisher:
ISBN:
Category : Galaxies
Languages : en
Pages : 25

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Summary: QSO absorption systems with damped Ly[alpha] lines have been suggested as the high-redshift progenitors of present-day disk galaxies. As part of a survey of element abundances and star-formation rates in these systems, long-slit, 1.5Å resolution spectroscopic observations of the Zem = 2.67 QSO 0836+113 were obtained. The first detection of a Ly[alpha] emission from a galaxy identified by its absorption signature is reported.

Author: Michael A. Dopita
Publisher: Springer Science & Business Media
ISBN: 3662058669
Category : Science
Languages : en
Pages : 445

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The reference work on astrophysics to provide a comprehensive introduction to the physics of Interstellar Matter. The objective of the book is to show how physics can be applied to the understanding and diagnosis of the phase structure, the physical conditions and the chemical make-up and evolution of the interstellar medium. Unlike other textbooks in the field, here a more systematic approach has been adopted based on the authors' lecture course experience. It is aimed primarily at those undertaking post-graduate courses, or those doing advanced projects as part of honours undergraduate courses in physics or astrophysics.

Author: Tianxing Jiang
Publisher:
ISBN:
Category : Cosmic abundances
Languages : en
Pages : 106

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Green pea galaxies are a class of rare, compact starburst galaxies that have powerful optical emission line [OIII]$\lambda$5007. They are the best low-redshift analogs of high-redshift (z$>$2) Lyman-alpha emitting galaxies (LAEs). They provide unique opportunities to study physical conditions in high-redshift LAEs in great detail. In this dissertation, a few physical properties of green peas are investigated. The first study in the dissertation presents star formation rate (SFR) surface density, thermal pressure in HII regions, and a correlation between them for 17 green peas and 19 Lyman break analogs, which are nearby analogs of high-redshift Lyman break galaxies. This correlation is consistent with that found from the star-forming galaxies at z $\sim$ 2.5. In the second study, a new large sample of 835 green peas in the redshift range z = 0.011 -- 0.411 are assembled from Data Release 13 of the Sloan Digital Sky Survey (SDSS) with the equivalent width of the line [OIII]$\lambda$5007 $>$ 300\AA\ or the equivalent width of the line H$\beta$ $>$ 100\AA. The size of this new sample is ten times that of the original 80 star-forming green pea sample. With reliable T$_e$-based gas-phase metallicity measurements for the 835 green peas, a new empirical calibration of R23 (defined as ([OIII]$\lambda$$\lambda$4959,5007 + [OII]$\lambda$$\lambda$3726,3729)/H$\beta$) for strong line emitters is then derived. The double-value degeneracy of the metallicity is broken for galaxies with large ionization parameter (which manifests as log([OIII]$\lambda$$\lambda$4959,5007/[OII]$\lambda$$\lambda$3726,3729) $\geq$ 0.6). This calibration offers a good way to estimate metallicities for extreme emission-line galaxies and high-redshift LAEs. The third study presents stellar mass measurements and the stellar mass-metallicity relation of 828 green peas from the second study. The stellar mass covers 6 orders of magnitude in the range 10$^{5}$ -- 10$^{11}$ M$_{\odot}$, with a median value of 10$^{8.8}$ M$_{\odot}$. The stellar mass-metallicity relation of green peas is flatter and displays about 0.2 - 0.5 dex offset to lower metallicities in the range of stellar mass higher than 10$^{8}$ M$_{\odot}$ compared to the local SDSS star-forming galaxies. A significant dependence of the stellar mass-metallicity relation on star formation rate is not found in this work.

Author: Jean-Baptiste Vielfaure
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Les sursauts-gamma (GRBs) sont parmi les événements cosmiques les plus brillants. Ces flashs de photons gamma de courte durée sont suivis d'une rémanence brillante observable des rayons X aux ondes radio. La classe des sursauts-gamma longs (LGRBs) est associée à la mort d'étoiles massives. Les LGRBs se produisent généralement dans des galaxies peu brillantes avec des taux de formation stellaire spécifiques élevés et des environnements à métallicité inférieure à la métallicité solaire. Leurs hôtes pourraient être représentatifs de la population de galaxies présente à l'époque de la réionisation, encore mal connue. L'utilisation des LGRBs comme sondes des galaxies dans l'Univers distant offre des avantages uniques : (i) le flash de photons gamma nous permet de détecter des galaxies à tous décalages spectraux indépendamment de leurs propriétés d'émission; (ii) grâce à leur forte luminosité, les LGRBs peuvent être utilisés comme des phares capables de révéler le milieu interstellaire (MIS) des galaxies même les plus faibles et les plus éloignées, en apportant des détails inaccessibles autrement; (iii) la rémanence des LGRBs s'estompe rapidement, permettant l'étude des galaxies hôtes. Le but de cette thèse est d'utiliser les LGRBs pour étudier certaines des propriétés des galaxies à formation d'étoiles, distantes et faibles. Pour cela, je combine les informations sur le MIS obtenues par les raies d'absorption présentes dans les spectres de rémanence à celles du gaz ionisé obtenues par les raies d'émission de la galaxie hôte. De plus, j'approfondis l'interprétation des données à l'aide de simulations numériques.La première partie de cette thèse montre que les LGRBs sont des outils puissants pour détecter l'échappement de photons ionisants de galaxies très faibles et caractériser les voies par lesquelles cela se produit.Je présente les résultats de l'observation d'émission LyC dans le spectre de rémanence d'un LGRB nouvellement découvert. Cette détection est complétée par les observations de deux autres galaxies hôtes de LGRBs pour lesquelles un échappement de LyC est connu, afin de déterminer leur fraction d'échappement en LyC et de comparer leurs propriétés. Les fractions d'échappement calculées le long de la ligne de visée du LGRB sont élevées, et augmentent le nombre de détections des émetteurs LyC, en particulier à des magnitudes absolues très faibles.La deuxième partie de mon travail est consacrée à l'étude de la population des galaxies hôtes de LGRB étant émetteurs Lyman-alpha (LAE). Je mets à jour le recensement de ces galaxies en fournissant une compilation de toutes les détections disponibles, et en déterminant les statistiques de LAEs à partir d'échantillons spectroscopiques de galaxies hôtes de LGRB et de rémanences.A partir de cette étude, je sélectionne un sous-échantillon de quatre galaxies pour lesquelles on peut mesurer les principaux paramètres nécessaires pour contraindre le modèle de coquille utilisé pour interpréter la raie d'émission Lyman-alpha.Le modèle donne des résultats inconsistants pour les LGRB-LAEs qui présentent les densités de colonne d'hydrogène neutre les plus élevées, pourtant typiques des hôtes de LGRB et des LGRB-LAEs.Ce résultat amène à une interprétation des informations sondées le long de la ligne de visée des LGRBs et de l'échappement des photons Lya. Enfin, ces résultats sont approfondis à travers la simulation numérique d'une galaxie à z=3 ayant des propriétés typiques des galaxies hôtes de LGRB. Je trouve que les photons Lyman-alpha s'échappent de plusieurs régions au sein de la galaxie plutôt que d'une seule région dominante jeune et active qui pourrait héberger le LGRB. Cette thèse montre que les observations de la rémanence des LGRBs et de leur galaxie hôte sont des outils puissants permettant d'explorer les propriétés des galaxies faibles et distantes.

Author: Josephine Victoria Kerutt
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Most of the matter in the universe consists of hydrogen. The hydrogen in the intergalactic medium (IGM), the matter between the galaxies, underwent a change of its ionisation state at the epoch of reionisation, at a redshift roughly between 6>z>10, or ~10^8 years after the Big Bang. At this time, the mostly neutral hydrogen in the IGM was ionised but the source of the responsible hydrogen ionising emission remains unclear. In this thesis I discuss the most likely candidates for the emission of this ionising radiation, which are a type of galaxy called Lyman alpha emitters (LAEs). As implied by their name, they emit Lyman alpha radiation, produced after a hydrogen atom has been ionised and recombines with a free electron. The ionising radiation itself (also called Lyman continuum emission) which is needed for this process inside the LAEs could also be responsible for ionising the IGM around those galaxies at the epoch of reionisation, given that enough Lyman continuum escapes. Through this mechanism, Lyman alpha and Lyman continuum ...