Download or read book Neutral Gas Properties of High redshift Analog Galaxies written by Alexandra Le Reste and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evolution of Neutral Hydrogen Properties of Galaxies With Respect to Large Scale Structure Over One Third the Age of the Universe written by Julia AM. Blue Bird and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We find that our data follow known scaling relations. Both theory and observations suggest that large-scale structure impacts galaxy evolution in addition to known trends in local density. We find that galaxy spins tend to be aligned with cosmic web filaments and a hint of the predicted transition mass associated with the spin angle alignment. With our second epoch of data from the CHILES survey, we probe the high-redshift regime. We present two new HI detections at z = 0.257 and z = 0.258, plus a stacked result at z ∼ 0.36. We combine these results with the previously published CHILES samples. This provides, for the first time, a continuous look at directly detected HI in emission over redshift range 0
Download or read book Low Redshift Damped Ly alpha Galaxies Toward the Quasars B2 0827 243 PKS 0952 179 PKS 1127 145 and PKS 1629 120 written by and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present optical and near-infrared ground-based imaging results on four low-redshift damped Ly-alpha (DLA) galaxies. The corresponding DLA systems were discovered in our Hubble Space Telescope spectroscopic surveys for DLA lines in known strong Mg ii absorption-line systems toward the quasars B2 0827+243, PKS 0952+179, PKS 1127 145, and PKS 1629+120. Two of the four DLA galaxies have confirmed slit redshifts, one has a photometric redshift consistent with the absorption-line redshift, and the fourth identification is based on the galaxy's proximity to the quasar sight line. The DLA galaxies span a mixture of morphological types from patchy, irregular, and low surface brightness to spiral galaxies. We also discovered several extremely red objects (EROs) in two of these fields and discuss the possibility that they are associated with the DLA galaxies. These observations add to the small but growing list of DLA galaxies at low redshift. At the present time, 14 DLA galaxies in the redshift range 0.05 smalller or approx. Z smaller or approx. 1 have been studied. The distributions of DLA galaxy properties for these 14 cases are discussed, and some important trends emerge. Low-luminosity dwarf galaxies with small impact parameters dominate this small sample. Also, four of the five highest column density systems, which dominate in the determination of the cosmological neutral gas mass density, arise in low surface brightness dwarf galaxies. Zwaan et al. have shown that only 15% of the neutral gas at the present epoch is contained in low surface brightness galaxies. Thus, if the low-redshift DLA galaxy trends hold up with larger samples, it would indicate that a different population of objects is responsible for the bulk of the neutral hydrogen gas in the universe at Z approx. 0.5.
Download or read book The Evolution of Galaxies Through the Neutral Hydrogen Window written by Robert Minchin and published by American Institute of Physics. This book was released on 2008-08-14 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: This conference brought together observers and theorists to discuss what we are learning from the current generation of extragalactic neutral hydrogen observations and what prospects lie ahead, with particular emphasis on the exciting prospects for the next 3 to 10 years with the major U.S. facilities.
Download or read book The Physical Conditions of Atomic Gas at High Redshift written by Marcel Neeleman and published by . This book was released on 2015 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we provide insight into the chemical composition, physical conditions and cosmic distribution of atomic gas at high redshift. We study this gas in absorption against bright background quasars in absorption systems known as Damped Ly-alpha Systems (DLAs). These systems contain the bulk of the atomic gas at high redshift and are the likely progenitors of modern-day galaxies. In Chapter 2, we find that the atomic gas in DLAs obeys a mass-metallicity relationship that is similar to the mass-metallicity relationship seen in star-forming galaxies. The evolution of this relationship is linear with redshift, allowing for a planar equation to accurately describe this evolution, which provides a more stringent constraint on simulations modeling DLAs. Furthermore, the concomitant evolution of the mass-metallicity relationship of atomic gas and star-forming galaxies suggests an intimate link between the two. We next use a novel way to measure the physical conditions of the gas by using fine-structure line ratios of singly ionized carbon and silicon. By measuring the density of the upper and lower level states, we are able to determine the temperature, hydrogen density and electron density of the gas. We find that the conditions present in this high redshift gas are consistent with the conditions we see in the local interstellar medium (ISM). A few absorbers have higher than expected pressure, which suggests that they probe the ISM of star-forming galaxies. Finally in Chapter 4, we measure the cosmic neutral hydrogen density at redshifts below 1.6. Below this redshift, the Ly-alpha line of hydrogen is absorbed by the atmosphere, making detection difficult. Using the archive of the Hubble Space Telescope, we compile a comprehensive list of quasars for a search of DLAs at redshift below 1.6. We find that the incidence rate of DLAs and the cosmic neutral hydrogen density is smaller than previously measured, but consistent with the values both locally and at redshifts of about 2. Altogether, these results improve our understanding of atomic gas at high redshift and help illuminate how this important component shapes the galaxies we see today.
Download or read book Detailed Properties of High Redshift Galaxies written by Tucker A. Jones and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Intergalactic Baryon Enrichment and Implications for Galaxy Evolution at High Redshift written by Thomas J. Cooper (Ph. D.) and published by . This book was released on 2018 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we present several surveys of heavy element absorber characteristics at high redshift, gauging properties of diffuse intra- and intergalactic gas in the first several Gyr of the Universe. At z ~ 3.5, we study chemical abundances of Lyman limit systems (LLSs) and evaluate their potential to represent expected reservoirs of cold, low-metallicity gas whose accretion onto galaxies is necessary to maintain star formation. In an initial survey focused only on LLSs identified as potential lowmetallicity absorbers, based on the absence of metal lines in low-resolution spectra, we indeed found the selected systems have low abundances, with a median of [M/H]~ -2.2 and several systems at [M/H]/~ -3, comparable to the intergalactic medium. While this result is tempting to interpret as evidence that a sizable fraction of LLSs are candidates of low-metallicity gas accreting onto galaxies, in a follow-up study of all LLSs at z ~ 3.5 we found that LLS abundances can be reasonably described by a unimodal distribution with [M/H]~ -2.5. Additional diagnostics are hence needed to evaluate if (and how many) low abundance LLSs arise from accretion flows, since the overall LLS abundance distribution overlaps heavily with the IGM at this epoch. In a seperate work that constitutes the largest study of multiple ions in individual metalline absorption systems at z /~ 6, we find that the bulk of high-redshift absorption systems are low-ionization and low-metallicity. Since H i absorption cannot be seen at z >/~ 6, we further argue from incidence rates and absorber characteristics that these absorbers are analogous to strong neutral hydrogen systems seen at lower redshift. We conclude that the non-detection of weaker H i absorption systems (such as LLSs) is consistent with lower metallicities and lower ionization states in the circumgalactic medium than is seen at later times.
Download or read book Properties of High redshift Galaxies in Different Environments written by Yohana Herrero Alonso and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding Large Scale Structure Galaxies and Ionized Gas at Z 2 3 written by Michael Weber Topping and published by . This book was released on 2020 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the nature and evolution of the high-redshift universe is crucial in forming complete models of galaxy evolution and large-scale structure formation. In this dissertation I investigate several aspects of the high-redshift universe, including the structure of a massive galaxy protocluster, understanding the nature and interplay between massive stars and ionized gas in high-redshift galaxies. First, I present an analysis of densely sampled spectroscopic observations of galaxies within the SSA22 protocluster at z~3.09 which reveal two distinct structures separated in redshift space and segregated on the sky. An analysis of similar structures within cosmological N-body simulations reveals that such a distribution of galaxies can only be explained as two nearby overdensities which will remain distinct as they evolve to z=0. Based on the N-body simulations, I find that the opportunity to observe such a phenomenon is incredibly rare, with an occurrence rate of 7.4 h^3 Gpc^ 3. In this dissertation I also investigate the differences between local and high-redshift galaxies suggested by the offset towards higher [OIII]5007/Hb and [NII]6584/Ha on the `BPT' diagram. I analyze combined rest-UV and rest-optical spectra of high-redshift galaxies. Crucially, rest-UV spectra provide a powerful constraint on the population of massive stars within high-redshift galaxies, which is an important driver powering the observed rest-optical emission lines. To investigate this origin of the offset on the BPT diagram, I construct two composite spectra composed of high-redshift galaxies at different locations on the BPT diagram. This analysis demonstrates that high-redshift galaxies that are more offset typically have younger stellar ages, lower stellar metallicities, higher ionization parameters, and are more alpha-enhanced compared to high-redshift galaxies that lie along the local sequence. In addition, this analysis reveals that even galaxies that are entirely consistent with the local nebular excitation sequence appear to be alpha-enhanced. This suggests that a similarity in the location of high-redshift and local galaxies in the BPT diagram may not be indicative of a similarity in their physical properties. I further expand upon this analysis by fitting the joint rest-UV and rest-optical properties of individual galaxies in the sample. An important aspect of analyzing individual galaxy spectra is a quantitative limit on how well we can fit the spectra. By introducing noise to model galaxy spectra which has known properties, and binding its best-fit properties, I determine that galaxy properties can be accurately reproduced if the spectrum has a SNR>4. The best-fit properties of individual galaxies in our sample reveals that they have comparable ionization parameters to those of local HII regions the share the same nebular metallicity. In addition, I find that all galaxies in the sample show evidence for being alpha-enhanced resulting in harder ionizing spectra compared to local galaxies. These results point toward the observed offset on the BPT diagram being primarily caused by a harder ionizing spectra at fixed nebular metallicity.
Download or read book Neutral Hydrogen In the Local Universe written by Ann Martin and published by . This book was released on 2011 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: We make use of the sensitivity and large sample size of the Arecibo Legacy Fast ALFA (ALFALFA) survey to investigate statistical properties of HI-selected galaxies in the local universe. This ongoing survey will eventually produce a census of over 30,000 gas-rich galaxies. The partial sample available for this work contains over 10,000 galaxies, making it twice as large as the previous generation blind HI survey, HIPASS. We have characterized the survey sensitivity and the selection function for use in the analyses presented in this dissertation, and are therefore able to make robust estimates of the characteristics of the galaxy population sampled by ALFALFA. From the available sample, we derive the HI mass function at redshift z = 0 via both the 1/Vmax and 2DSWML methods, which are in extremely close agreement with each other. These measurements are influenced by the survey design and the cosmological volume sampled, and we investigate and describe the magnitude and characteristics of the imprint of large-scale structure, survey sensitivity, and distance errors on the HI mass function. Our finding that there are more galaxies with high HI masses on the extreme end of the distribution will alter predictions for future large-scale 21 cm line surveys with such instruments as the Square Kilometer Array (SKA). The large volume and sample size of ALFALFA also allows study of the dependence of the HI mass function on galaxy environments at various scales by splitting into subsamples. This work confirms that the distribution of HI mass does change with environment and indicates that there is some threshold density beyond which the HI reservoirs of dwarf galaxies are efficiently removed, thereby flattening the HI mass function. The scale and degree of clustering for HI-selected galaxies is probed through the galaxy-galaxy two-point correlation function. Again, the large size of the ALFALFA galaxy catalog allows the sample to be split. The correlation function can thus be investigated as a function of HI mass, resolving a discrepancy from the HIPASS analysis, and as a function of optical luminosity and color. We find that HI-selected galaxies, and low HI mass galaxies in particular, are the most weakly clustered population of galaxies known to exist. For HI-selected galaxies, hydrogen mass more reliably distinguishes between environments on large scales than optical properties do, but on small scales these galaxies cluster similarly regardless of HI mass. The clustering scale of HI-selected galaxies at low redshift will help to disentangle the influence of environment on galaxy evolution, and to constrain the populations to which future large 21 cm line surveys will be sensitive. The robust measurement of the statistical properties of gas-rich galaxies at low redshifts provided in this dissertation will be used to improve simulations and models that predict the characteristics of this population of galaxies. In the case of the correlation function, we show that the clustering observed in ALFALFA can distinguish between popular models of star formation that predict the present-day distribution of gas in simulated galaxies. We suggest future projects that will further our understanding of the interplay between HI and optical properties and galaxy environment, while also providing robust observables for comparison to models.
Download or read book The Spectral Energy Distribution of Galaxies SED 2011 IAU S284 written by Richard J. Tuffs and published by Cambridge University Press. This book was released on 2012-08-30 with total page 533 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent observational developments are providing the first truly panchromatic view of galaxies, extending from the radio to TeV gamma-rays. This is motivating the development of new models for the interpretation of spectral energy distributions (SEDs) of galaxies in terms of the formation, evolution and emission of stellar and accretion-driven sources of photons, the interaction of the photons with the gaseous and dust components of the interstellar medium, and high-energy processes involving cosmic rays. IAU Symposium 284 details progress in the development of such models, their relation to fundamental theory, and their application to the interpretation of the panchromatic emission from the Milky Way and nearby galaxies, connecting the latter with models for the evolution of the SEDs of distant galaxies, and the extragalactic background light. IAU S284 is a useful resource for all researchers working with the copious amounts of multiwavelength data for galaxies now becoming available.
Download or read book Understanding the Epoch of Cosmic Reionization written by Andrei Mesinger and published by Springer. This book was released on 2015-11-28 with total page 292 pages. 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?
Download or read book The Morphological Kinematic and Halo Gas Properties of MgII Absorption Selected Galaxies at Intermediate Redshift written by Glenn George Kacprzak and published by . This book was released on 2008 with total page 558 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structural and Physical Properties of High Redshift Galaxies in the Hubble Ultra Deep Field written by Nimish P. Hathi and published by . This book was released on 2008 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Outskirts of Galaxies written by Johan H. Knapen and published by Springer. This book was released on 2017-07-09 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and accretion as observed through deep imaging and spectroscopy, and guide the reader through the various formation and evolution scenarios for galaxies. The reviews focus on the major open questions in the field, and explore how they can be tackled in the future. This book provides a unique entry point into the field for graduate students and non-specialists, and serves as a reference work for researchers in this exciting new field.
Download or read book Galaxies at High Redshift written by I. Pérez-Fournon and published by Cambridge University Press. This book was released on 2010-06-24 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers normal galaxies, distant galaxies, studies based on far-infrared diagnostics, quasar absorption lines, and the properties of nearby galaxies. The timely volume provides an essential reference for astronomers working in the field of high-redshift galaxies. It includes the lectures delivered at the XI Canary Islands Winter School of Astrophysics, and reviews scientific results as well as main questions in the field.
Download or read book High Redshift Galaxies as Probes of the Epoch of Reionization written by Jessie Frances Taylor and published by . This book was released on 2016 with total page 388 pages. 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.
