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Our knowledge of galaxy formation and evolution has exploded over the past few decades and we are now in an era of large galaxy surveys consisting of millions of galaxies. These samples enable statistical characterization of galaxy populations, helping to empirically explore the manner in which galaxies evolve through time. Current and future missions will push the envelope further by identifying millions of galaxies, many of which will be selected via their strong emission lines. We are motivated to develop ever-more sophisticated statistical methods to extract the maximal amount of information from these surveys. In Chapter 2, I describe the details of identifying a large sample of z~2 galaxies selected from Hubble Space Telescope (HST) grism frames on the basis of their strong rest-frame optical emission lines, with [O III] being the strongest in the vast majority of these systems. I also present the basis physical properties of the sample, including their rest-frame UV and optical size, stellar mass, UV-based star formation rate (SFR), and dust content. In order to provide context for how this emission-line galaxy (ELG) sample relates to the broader galaxy population at this epoch, I identify a comparison sample selected on the basis of their photometric redshifts and compare the two samples' physical properties. The ELG sample has systematically lower stellar masses, SFRs, and dust contents compared to the photometric redshift sample. This comparison indicates that identifying galaxies on the basis of their strong emission lines is an efficient way to find low-mass systems but is biased against objects with large amounts of dust. In Chapter 3, I measure the luminosity function and star-formation rate density of the sample introduced in Chapter 2. This measurement directly informs the observing strategy that is required for upcoming missions, which will use rest-frame optical ELGs to measure the large scale structure of the Universe. Since the precision in this measurement is directly related to the number of sources that are identified, accurate estimates of the line luminosity function are essential for designing the observing strategies of these flagship missions. I introduce a new, flexible spectral energy distribution (SED) code, MCSED, in Chapter 4. This galaxy fitting tool is specifically optimized to allow for varying assumptions about the physics and interplay of stars, dust, and gas in galaxies. Since the properties of these various components change with redshift and host galaxy type, and are constantly being improved from both an empirical and theoretical standpoint, flexible SED fitting tools are essential for extracting the maximal amount of science from new surveys. I apply this code to the z~2 galaxy sample introduced in Chapter 2 using a flexible model with multiple parameters to describe the dust attenuation and star formation history. The sample exhibits clear evolution in the star formation histories, dust contents, and average spectra across the three orders of magnitude in stellar mass. As the stellar mass increases, the objects become redder due to both a higher dust content and a larger population of old, red stars. Finally, Chapter 5 presents an expanded framework for fitting the SEDs of galaxies that accounts for correlated and non-Gaussian uncertainties in the photometric flux measurements. Such covariances are nearly universal in modern techniques for measuring photometry, yet these correlations have not been taken into account in SED fitting until now. This method for propagating variances and covariances throughout the analysis pipeline will be particularly important for upcoming high-precision cosmology experiments that rely upon photometric redshifts.
The focus of this dissertation is to study resolved substructures in galaxies at kpc-scale and their relation with the global properties of the host galaxy using combined high resolution photometric data from the Hubble Space Telescope and very deep long exposure spectroscopic observations with the Keck telescopes. I use the optical and near-infrared data taken as part of the CANDELS project to perform pixel-by-pixel analysis of 120 galaxies at intermediate redshifts. I produce resolved rest-frame (U-V) color, stellar mass and star formation rate surface densities, stellar age and extinction maps and profiles along the galaxies rotation axes. I study physical properties of clumps and quantify their spatial distribution and covering fraction. Investigating the evolution of covering fraction and average radial distance with respect to both redshift and stellar mass of the host galaxy, suggests that if the central bulge growth is due to migration of stellar clumps, it should have happened at higher redshifts. I find that there exists a tight correlation between the stellar mass and star formation rate surface densities of pixels inside individual galaxies as well as among red and blue clumps over different galaxies. The tightness of the blue clumps main sequence regardless of the large redshift rang of the hosts, suggests no evolution in the nature of blue clumps with time. I estimate small-scale distribution of stellar dust extinction from pixel-by-pixel SED fitting and used H[Alpha]/ H[Beta] nebular emission line ratios from Keck/DEIMOS spectra at each spatial resolution element to measure attenuation faced by ionized gas at different radii from the center of galaxies. I find a good agreement between the integrated and median of resolved color excess measurements in the galaxies. I find that inclination plays an important role in the variation of the nebular to stellar color excess ratio. I find that the nebular color excess increases with stellar mass surface density. This explains the absence of radial trend in the nebular color excess in lower mass galaxies. I also demonstrate the usefulness of resolved optical line ratio plots in identifying otherwise hidden AGNs.
This thesis addresses two of the central processes which underpin the formation of galaxies: the formation of stars and the injection of energy into the interstellar medium from supernovae, called feedback. In her work Claudia Lagos has completely overhauled the treatment of these processes in simulations of galaxy formation. Her thesis makes two major breakthroughs, and represents the first major steps forward in these areas in more than a decade. Her work has enabled, for the first time, predictions to be made which can be compared against new observations which probe the neutral gas content of galaxies, opening up a completely novel way to constrain the models. The treatment of feedback from supernovae, and how this removes material from the interstellar medium, is also likely to have a lasting impact on the field. Claudia Lagos Ph.D. thesis was nominated by the Institute for Computational Cosmology at Durham University as an outstanding Ph.D. thesis 2012.
This volume presents lectures of the XI Canary Islands Winter School of Astrophysics written by experts in the field.
One of the most attractive features of the young discipline of Space Science is that many of the original pioneers and key players involved are still available to describe their field. Hence, at this point in history we are in a unique position to gain first-hand insight into the field and its development. To this end, The Century of Space Science, a scholarly, authoritative, reference book presents a chapter-by-chapter retrospective of space science as studied in the 20th century. The level is academic and focuses on key discoveries, how these were arrived at, their scientific consequences and how these discoveries advanced the thoughts of the key players involved. With over 90 world-class contributors, such as James Van Allen, Cornelis de Jager, Eugene Parker, Reimar Lüst, and Ernst Stuhlinger, and with a Foreword by Lodewijk Woltjer (past ESO Director General), this book will be immensely useful to readers in the fields of space science, astronomy, and the history of science. Both academic institutions and researchers will find that this major reference work makes an invaluable addition to their collection.
Thoroughly revised and expanded throughout, the new edition is a graduate-level text and reference book on gaseous nebulae, nova and supernova remnants. Much of the new data and new images are from the Hubble Space Telescope with two wholly new chapters being added along with other new features. The previous edition which was tried and tested for thirty years has now been succeeded by a revised, updated, larger edition, which will be valuable to anyone seriously interested in astrophysics.
Galaxies, along with their underlying dark matter halos, constitute the building blocks of structure in the Universe. Of all fundamental forces, gravity is the dominant one that drives the evolution of structures from small density seeds at early times to the galaxies we see today. The interactions among myriads of stars, or dark matter particles, in a gravitating structure produce a system with fascinating connotations to thermodynamics, with some analogies and some fundamental differences. Ignacio Ferreras presents a concise introduction to extragalactic astrophysics, with emphasis on stellar dynamics, and the growth of density fluctuations in an expanding Universe. Additional chapters are devoted to smaller systems (stellar clusters) and larger ones (galaxy clusters). Fundamentals of Galaxy Dynamics, Formation and Evolution is written for advanced undergraduates and beginning postgraduate students, providing a useful tool to get up to speed in a starting research career. Some of the derivations for the most important results are presented in detail to enable students appreciate the beauty of maths as a tool to understand the workings of galaxies. Each chapter includes a set of problems to help the student advance with the material.
The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of the chemical evolution of the Milky Way, spheroidal galaxies, irregular galaxies and of cosmic chemical evolution. The aim of this book is to provide an introduction to students as well as to amend our present ideas in research; the book also summarizes the efforts made by authors in the past several years in order to further future research in the field.
A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.