Download or read book Analyzing the Rest frame Optical Emission line and Host Galaxy Properties Of written by Jordan Nathaniel Runco and published by . This book was released on 2022 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of galaxies across multiple epochs is essential for understanding the evolution of the universe. One key time period to study is z ∼ 2, when star formation activity in the universe is at its peak. Comparing local galaxies to those in this more active time period is a critical way to learn about galaxy evolution by examining the differences and/or similarities in galaxy properties. In this thesis, I study the rest-frame optical emission-line and host galaxy properties of star-forming galaxies at z ∼ 2 in the MOSFIRE Deep Evolution Field (MOSDEF) survey to better understand the evolution of galaxies over the past 10 Gyr of our universe's history. First, I investigate correlations between the emission-line properties and the physical and chemical properties of z ∼ 2 star-forming galaxies in the MOSDEF survey. It is necessary to understand the known offset of z > 1 galaxies on the [O III][lambda]5008/H[Beta] vs. [N II][lambda]6585/H[alpha] ([N II] "BPT") diagram compared to their local counterparts because strong rest-optical emission-lines are commonly used to infer a variety of galaxy properties (e.g. gas-phase oxygen abundance). To investigate the physical driver of this shift, I defined two populations of z ∼ 2 MOSDEF galaxies on the [N II] BPT diagram, one on and one off (i.e., offset from) the local sequence. I find that these two groups remain separated on the [O III][lambda]5008/H[Beta] vs. [S II][lambda][lambda]6718,6733/H[alpha] ([S II] BPT) diagram and the [O III][lambda][lambda]4960,5008/[O II][lambda][lambda]3727,3730 vs. ([O III][lambda][lambda]4960,5008+[O II][lambda][lambda]3727,3730)/H[Beta] (O 32 vs. R 23 ) diagram, which suggests that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. Such a phenomenon may be tied to [alpha]-enhancement and massive stars that are chemically "young." Second, I compare the z ∼ 2 MOSDEF survey with the z ∼ 2 portion of the Keck Baryonic Structure Survey (KBSS) that has been observed with MOSFIRE. Like MOSDEF, KBSS studies a large sample of star-forming galaxies at z ∼ 2 with the MOSFIRE instrument; however, there are notable differences in survey construction and key results (e.g., the magnitude of the offset from the local star-forming sequence on the [N II] BPT diagram). Using consistent spectral-energy-distribution (SED) modeling for both surveys reveals that the MOSDEF z ∼ 2 targeted sample has a higher median stellar mass, lower star-formation rate (SFR) and specific SFR, and redder U−V color compared to KBSS. However, the subsets of the surveys that have been analyzed in previous work with high S/N spectra and multiple emission lines detected are strikingly similar. Aside from stellar population age, all sample properties investigated agree within the median uncertainties. Additionally, applying uniform stellar Balmer absorption correction and emission-line fitting techniques for both samples results in the same offset on the [N II] BPT diagram. I find that the previously believed differences in key results between the two surveys can be attributed toutilizing different SED and emission-line fitting techniques. Third, I analyze the completeness of the MOSDEF z ∼ 2 survey. Specifically, I use SED modeling and composite spectra created from spectral stacking to test if the subset of the MOSDEF z ∼ 2 star-forming galaxies with high S/N spectra is representative of the complete sample of star-forming galaxies. I find that the host galaxy and emission-line properties (most notably offset from the local SDSS sequence on the [N II] BPT diagram) are very similar, indicating that the smaller spectroscopic samples are representative of the full catalog of star-forming galaxies. Additionally, comparing galaxy properties obtained through SED modeling reveals that the z ∼ 2 sample observed by MOSDEF is representative of all z ∼ 2 galaxies that met the selection criteria for the MOSDEF survey. Taken together, these results reveal that the emission-line trends established using high S/N z ∼ 2 detection samples of star-forming galaxies in MOSDEF studies to date are representative of the rest-optical-magnitude-limited star-forming galaxy population at z ∼ 2. Fourth, I focus on two actively merging galaxies in the MOSDEF survey at z = 1.89. We model the SEDs of the merging galaxies to find that they are both massive with low SFRs and similar stellar population ages. Additionally, the star formation in both galaxies began and peaked within a few hundred Myr of each other, suggesting that their bursts of star formation may be connected. For one of these galaxies, GOODS-S 43114, Sérsic profile fitting and a relatively low velocity dispersion estimate indicates that it is a face-on disk; therefore, it will likely undergo a large structural change as it evolves into a massive, slowly-rotating elliptical galaxy in the present day. Finally, as an earlier part of research I used far-IR Herschel/PACS spectra to investigate the profiles of six OH doublets for a large sample of 178 local galaxies. I assembled ancillary data to probe AGN luminosity, radiation field hardness, dust temperature, and dust obscuration, and find correlations between the EW(OH) and these galaxy observables. Additionally, I comment on how the origin of emission for these OH doublets, whether from radiative pumping by infrared photons or from collisional excitation, may influence these relationships.

Download or read book The X ray Background written by Xavier Barcons and published by Cambridge University Press. This book was released on 1992-07-31 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of the current observational knowledge and understanding of the cosmic X-ray background.

Download or read book Resolved KPC scale Properties of Emission line Galaxies at Intermediate Redshifts written by Shoubaneh Hemmati and published by . This book was released on 2015 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Galaxies at High Redshift written by I. Pérez-Fournon and published by Cambridge University Press. This book was released on 2003-03-20 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents lectures of the XI Canary Islands Winter School of Astrophysics written by experts in the field.

Download or read book Robust Estimation of the Physical Properties of Z 2 Emission line Galaxies written by Will Bowman and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Science With The Cherenkov Telescope Array written by The Cta Consortium and published by World Scientific. This book was released on 2018-12-31 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes the science to be carried out by the upcoming Cherenkov Telescope Array, a major ground-based gamma-ray observatory that will be constructed over the next six to eight years. The major scientific themes, as well as core program of key science projects, have been developed by the CTA Consortium, a collaboration of scientists from many institutions worldwide.CTA will be the major facility in high-energy and very high-energy photon astronomy over the next decade and beyond. CTA will have capabilities well beyond past and present observatories. Thus, CTA's science program is expected to be rich and broad and will complement other major multiwavelength and multimessenger facilities. This book is intended to be the primary resource for the science case for CTA and it thus will be of great interest to the broader physics and astronomy communities. The electronic version (e-book) is available in open access.

Download or read book The Analysis of Emission Lines written by Space Telescope Science Institute (U.S.). Symposium and published by Cambridge University Press. This book was released on 1995-10-19 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: What can emission lines tell us about an astrophysical object? A workshop at the Space Telescope Science Institute was dedicated to address just this question - for a host of objects (including planetary nebulae and active galactic nuclei) across a broad range of wavelenghts (from the infrared through to gamma-rays). Sixteen review articles are presented in this volume. They provide an overview of technical data, techniques in and applications of the study of emission lines from a variety of objects.

Download or read book Astrophysics Of Gas Nebulae and Active Galactic Nuclei written by Donald E. Osterbrock and published by University Science Books. This book was released on 2006 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Dynamics of Galaxies written by Giuseppe Bertin and published by Cambridge University Press. This book was released on 2014-04-21 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides advanced students with an introduction to modern galactic dynamics, and equips them with useful observational and theoretical tools.

Download or read book The Physics and Evolution of Active Galactic Nuclei written by Hagai Netzer and published by Cambridge University Press. This book was released on 2013-09-16 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.

Download or read book AGN Feedback in Galaxy Formation written by Vincenzo Antonuccio-Delogu and published by Cambridge University Press. This book was released on 2010-10-28 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past decade, convincing evidence has been accumulated concerning the effect of active galactic nuclei (AGN) activity on the internal and external environment of their host galaxies. Featuring contributions from well-respected researchers in the field, and bringing together work by specialists in both galaxy formation and AGN, this volume addresses a number of key questions about AGN feedback in the context of galaxy formation. The topics covered include downsizing and star-formation time scales in massive elliptical galaxies, the connection between the epochs of supermassive black hole growth and galaxy formation and the question of whether AGN and star formation coexist. Authors also discuss key challenging computational problems, including jet-interstellar/intergalactic medium interactions, and both jet- and merging-induced star formation. Suitable for researchers and graduate students in astrophysics, this volume reflects the engaging and lively discussions taking place in this emerging field of research.

Download or read book The Nature of Dust Obscured Galaxies at Z2 written by Robert Shane Bussmann and published by . This book was released on 2010 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: I use observational evidence to examine the nature and role in galaxy evolution of a population of dust-obscured galaxies (DOGs) at z ̃2. These objects are selected with theSpitzer Space Telescope, are bright in the mid-infrared (mid-IR) but faint in the optical, and contribute a significant fraction of the luminosity density in the universe at z ̃2. The first component of my thesis is a morphological study using high spatial resolution imaging with theHubble Space Telescopeof two samples of DOGs. One set of 33 DOGs have mid-IR spectral features typical of an obscured active galactic nucleus (AGN) (called power-law DOGs), while the other set of 20 DOGs have a local maximum in their spectral energy distribution (SED) at rest-frame 1.6 m u;m associated with stellar emission (called bump DOGs). The host galaxy dominates the light profile in all but two of these DOGs. In addition, bump DOGs are larger than power-law DOGs and exhibit more diffuse and irregular morphologies; these trends are consistent with expectations from simulations of major mergers in which bump DOGs evolve into power-law DOGs. The second component of my thesis is a study of the dust properties of DOGs, using sub-mm imaging of 12 power-law DOGs. These power-law DOGs are hyper-luminous (2x1013 L_sun) and have predominantly warm dust (T_dust>35-60 K). These results are consistent with an evolutionary sequence in which power-law DOGs represent a brief but important phase when AGN feedback heats the interstellar medium and quenches star-formation. The third component of my thesis is a study of the stellar masses and star-formation histories of DOGs, using stellar population synthesis models and broad-band photometry in the rest-frame ultra-violet, optical, and near-IR. The best-fit quantities indicate bump DOGs are less massive than power-law DOGs. The relatively low stellar masses found from this line of analysis favor a merger-driven origin for ULIRGs at z ̃2.

Download or read book The Impact of HST on European Astronomy written by F. Duccio Macchetto and published by Springer Science & Business Media. This book was released on 2010-01-14 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Remembrance of Things Past It scarcely seems credible that it was almost exactly thirty years ago that I ?rst met Duccio Macchetto at the ?rst meeting of the newly formed Science Working Group of what was then called the Space Telescope project. We were there in slightly d- ferent roles, Duccio as the project scientist for the Faint Object Camera and I as an interdisciplinary scientist. Henk van de Hulst was also there as the of?cial rep- sentative of ESO. The approval of the project was the end result of a great deal of lobbying and politicking both in the USA and Europe, the European contribution proving essential to the approval process in the USA. Those interested in the nit- gritty of the process should read Robert Smith’s outstanding history of the Hubble Space Telescope. We should have realized early on that we were in for a rough time. At that ?rst meeting of the Science Working Group I remember vividly NASA Headquarters telling us that the Space Telescope was a success-oriented programme that would cost M$ 680. Well, we could live with the cost-tag, but we should have had concerns about the expression “success-oriented”. This meant that everything should turn out exactly as planned, the project would be carried out within the projected time-scale and budget and the telescope would be launched in 1983. Well, the rest is history. We learned a lot of useful jargon along the way.

Download or read book Astrophysics of the Diffuse Universe written by Michael A. Dopita and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book The Many Facets of Cosmic Explosions written by Alicia Soderberg and published by Universal-Publishers. This book was released on 2007-10 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past few years, long-duration gamma-ray bursts (GRBs), including the subclass of X-ray flashes (XRFs), have been revealed to be a rare variety of Type Ibc supernova (SN Ibc). While all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by many orders of magnitude. The observed diversity of stellar death corresponds to large variations in the energy, velocity, and geometry of the explosion ejecta. Using multi-wavelength (radio, optical, X-ray) observations of the nearest GRBs, XRFs, and SNe Ibc, I show that GRBs and XRFs couple at least 1048 erg to relativistic material while SNe Ibc typically couple less than 1048 erg to their fastest (albeit non-relativistic) outflows. Specifically, I find that less than 3 percent of local SNe Ibc show any evidence for association with a GRB or XRF. Interestingly, this dichotomy is not echoed by the properties of their optical SN emission, dominated by the radioactive decay of Nickel-56; I find that GRBs, XRFs, and SNe Ibc show significant overlap in their optical peak luminosity and photospheric velocities. Recently, I identified a new class of GRBs and XRFs that are under-luminous in comparison with the statistical sample of GRBs. Owing to their faint high-energy emission, these sub-energetic bursts are only detectable nearby (z

Download or read book An Introduction to Active Galactic Nuclei written by Bradley M. Peterson and published by Cambridge University Press. This book was released on 1997-02-13 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: How can we test if a supermassive black hole lies at the heart of every active galactic nucleus? What are LINERS, BL Lacs, N galaxies, broad-line radio galaxies and radio-quiet quasars and how do they compare? This timely textbook answers these questions in a clear, comprehensive and self-contained introduction to active galactic nuclei - for graduate students in astronomy and physics. The study of AGN is one of the most dynamic areas of contemporary astronomy, involving one fifth of all research astronomers. This textbook provides a systematic review of the observed properties of AGN across the entire electromagnetic spectrum, examines the underlying physics, and shows how the brightest AGN, quasars, can be used to probe the farthest reaches of the Universe. This book serves as both an entry point to the research literature and as a valuable reference for researchers in the field.

Download or read book Multiwavelength Mapping of Galaxy Formation and Evolution written by Alvio Renzini and published by Springer Science & Business Media. This book was released on 2005-05-23 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: The possibilities of astronomical observation have dramatically increased over the last decade. Major satellites, like the Hubble Space Telescope, Chandra and XMM Newton, are complemented by numerous large ground-based observatories, from 8m-10m optical telescopes to sub-mm and radio facilities. As a result, observational astronomy has access to virtually the whole electromagnetic spectrum of galaxies, even at high redshifts. Theoretical models of galaxy formation and cosmological evolution now face a serious challenge to match the plethora of observational data. In October 2003, over 170 astronomers from 15 countries met for a 4-day workshop to extensively illustrate and discuss all major observational projects and ongoing theoretical efforts to model galaxy formation and evolution. This volume contains the complete proceedings of this meeting and is therefore a unique and timely overview of the current state of research in this rapidly evolving field.