DOCSLIB.ORG

UCLA Electronic Theses and Dissertations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
UCLA Electronic Theses and Dissertations UCLA UCLA Electronic Theses and Dissertations Title Galaxies at the Epoch of Reionization Permalink https://escholarship.org/uc/item/39t4d9qg Author Mason, Charlotte Publication Date 2018 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA Los Angeles Galaxies at the Epoch of Cosmic Reionization A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Astronomy by Charlotte Ann Mason 2018 © Copyright by Charlotte Ann Mason 2018 ABSTRACT OF THE DISSERTATION Galaxies at the Epoch of Cosmic Reionization by Charlotte Ann Mason Doctor of Philosophy in Astronomy University of California, Los Angeles, 2018 Professor Tommaso L. Treu, Chair The reionization of intergalactic hydrogen in the universe's first billion years was likely driven by the first stars and galaxies, so its history encodes information about their prop- erties. But the timeline of reionization is not well-measured and it is still unclear whether galaxies alone can produce the required ionizing photons. In my thesis I have focused on two ways to use galaxies at our current observational frontiers to constrain reionization and high redshift galaxy evolution. One tool is the UV luminosity function (LF), which traces the evolution of star-forming galaxies and their ionizing photons. Accurately measuring LFs and understanding their evolution are important for understanding the connections between galaxies and their dark matter halos. I developed a simple, but powerful, semi-analytic model for LF evolution assuming star formation is driven by dark matter accretion. This has proved remarkably consistent with observations, and implies the majority of star formation at high redshifts occurs in low mass galaxies. I also developed a technique to improve the accuracy of LF by accounting for gravitational lensing magnification bias. Secondly, Lyman alpha (Lyα) emission from galaxies can probe the intergalactic medium (IGM) ionization state as Lyα photons are strongly attenuated by neutral hydrogen, but this requires disentangling physics on pc to Gpc scales. I developed a new forward-modeling Bayesian framework combining cosmological IGM simulations with interstellar medium mod- els to infer the IGM neutral hydrogen fraction from observations of Lyα emission. My thesis ii presents new measurements of the neutral fraction at z 7 and z 8, which, along with ∼ ∼ other independent constraints, provide increasing evidence for the bulk of reionization oc- curring at z 6 8. This is consistent with reionization being driven by ultra-faint galaxies ∼ − with a low average ionizing photon escape fraction. We also show that reionization impacts Lyα emission from different galaxy populations in different ways: UV bright galaxies living in overdense regions that reionize early have potentially visible Lyα even in a highly neutral IGM. The upcoming James Webb Space Telescope was designed to observe galaxies at Cosmic Dawn. Throughout this thesis I have made predictions for what JWST may observe in the context of high redshift galaxy evolution. iii The dissertation of Charlotte Ann Mason is approved. Steven R. Furlanetto Matthew A. Malkan Smadar Naoz Tommaso L. Treu, Committee Chair University of California, Los Angeles 2018 iv TABLE OF CONTENTS 1 Introduction :::::::::::::::::::::::::::::::::::::: 1 1.1 Galaxy UV luminosity functions . .2 1.2 Lyman alpha emission from galaxies as a probe of reionization . .4 2 The Galaxy UV Luminosity Function Before the Epoch of Reionization 8 2.1 Introduction . .9 2.2 Model Description . 12 2.2.1 Star formation prescription . 13 2.2.2 Dust extinction . 15 2.2.3 Calibration . 17 2.3 Results . 17 2.3.1 Stellar masses and ages . 17 2.3.2 Luminosity functions and SFR density . 20 2.3.3 Forecasts for JWST and WFIRST ................... 22 2.3.4 Implications for reionization . 26 2.4 Summary and Conclusions . 31 3 Correcting the z 8 Galaxy Luminosity Function for Gravitational Lensing ∼ Magnification Bias :::::::::::::::::::::::::::::::::::: 34 3.1 Introduction . 35 3.2 Data . 38 3.2.1 The BoRG Survey . 38 3.2.2 Massive Foreground Galaxies Acting as Deflectors . 39 3.2.3 The Millennium Simulation . 40 v 3.3 Theoretical Background . 41 3.3.1 Galaxy Luminosity Function . 41 3.3.2 Strong Lensing . 41 3.3.3 Weak Lensing . 42 3.3.4 Magnification Bias . 43 3.4 Strong and Intermediate Lensing . 45 3.4.1 Strong Lensing by an Evolving Deflector Population . 45 3.4.2 Identifying Significantly Magnified Sources . 53 3.5 Weak Lensing . 58 3.5.1 Estimating Magnification from Simulation Catalogs . 58 3.5.2 BoRG Weak Lensing Magnification PDFs . 60 3.6 Recomputing the LF . 60 3.6.1 Bayesian Estimation of the LF . 61 3.6.2 Including the Lensing Corrections . 62 3.7 Results . 63 3.7.1 Strong and Intermediate Lensing Events in the BoRG Survey . 64 3.7.2 Inference of the Intrinsic z 8LF.................... 64 ∼ 3.7.3 Predictions for z > 8 and Future Surveys . 66 3.8 Summary and Conclusion . 68 3.9 Appendix: Bayesian Framework for Estimating the luminosity function . 70 4 The Universe is Reionizing at z 7: Bayesian Inference of the IGM Neutral ∼ Fraction Using Lyα Emission from Galaxies :::::::::::::::::::: 80 4.1 Introduction . 81 4.2 ISM, CGM, and IGM Radiative Transfer Modeling . 85 vi 4.2.1 ISM Lyα radiative transfer . 85 4.2.2 IGM and CGM Lyα Radiative Transfer . 95 4.3 Bayesian Inference . 102 4.3.1 Generating the likelihood . 104 4.4 Results . 106 4.4.1 Large samples of galaxies can accurately constrain the neutral fraction 107 4.4.2 Inference from current data . 108 4.4.3 Predictions for JWST . 114 4.5 Discussion . 117 4.5.1 The global reionization history . 117 4.5.2 A sudden drop in Lyα emission { redshift evolution of ∆v?...... 119 4.5.3 Lyα from UV bright galaxies { redshifted away from resonance? . 120 4.6 Summary and Conclusions . 121 5 Beacons into the Cosmic Dark Ages: Boosted transmission of Lyα from UV bright galaxies at z > 7 ::::::::::::::::::::::::::::::: 124 ∼ 5.1 Introduction . 125 5.2 Method . 126 5.3 Results . 128 5.3.1 Boosted transmission of Lyα from massive halos . 128 5.3.2 Evolving Lyα fraction for UV bright galaxies . 132 5.3.3 UV bright galaxies as probes of reionization . 133 5.4 Discussion . 135 5.5 Summary and Conclusions . 136 6 First Results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS): vii Kinematics of Lensed Galaxies at Cosmic Noon ::::::::::::::::: 138 6.1 Introduction . 139 6.2 The KMOS Lens-Amplified Spectroscopic Survey . 142 6.3 Observations and Data . 143 6.3.1 Target selection . 143 6.3.2 Observations and data reduction . 144 6.4 Analysis and Results . 144 6.4.1 Comparison of HST grism and ground-based flux measurements . 145 6.4.2 Photometric properties and gravitational lens modeling . 148 6.4.3 Kinematics . 153 6.4.4 Star formation drivers . 159 6.4.5 Kinematic trends . 163 6.5 Discussion . 167 6.5.1 What is the dynamical nature of galaxies at z > 1? . 167 ∼ 6.5.2 Revealing the kinematics of low mass galaxies . 168 6.5.3 What are dispersion dominated galaxies? . 169 6.6 Conclusions . 170 6.7 Appendix: Kinematic Maps . 172 6.8 Appendix: Rotation Curves . 178 7 Inferences on the Timeline of Reionization at z 8 From the KMOS Lens- ∼ Amplified Spectroscopic Survey ::::::::::::::::::::::::::: 181 7.1 Introduction . 182 7.2 Observations . 184 7.2.1 The KMOS Lens-Amplified Spectroscopic Survey . 184 viii 7.2.2 Target selection . 186 7.2.3 KLASS observing strategy and reduction . 189 7.2.4 Reduction . 189 7.3 Emission Line Search, Purity and Completeness . 191 7.3.1 Emission line detection technique . 191 7.3.2 Candidate emission lines and sample purity . 192 7.3.3 Completeness . 194 7.3.4 Flux and equivalent width limits . 198 7.4 Reionization inference . 199 7.4.1 Bayesian inference framework . 199 7.4.2 Defining a selection function for a photometric sample . 202 7.4.3 Inference on the IGM neutral fraction . 209 7.5 Discussion . 210 7.5.1 The timeline of reionization . 214 7.5.2 M1149 JD1 { Lyα emission at z = 9:11? . 217 7.5.3 Other UV emission lines at z 8.................... 219 ∼ 7.5.4 Background limited observations with KMOS . 220 7.6 Summary and Conclusions . 223 7.7 Independent confirmation of CIV emission at z = 6:11 . 225 7.8 Testing the selection function of our final sub-sample . 227 7.9 Reionization Inference . 231 7.9.1 Likelihood at one.
Load more

Recommended publications
  • Constructing a Galactic Coordinate System Based on Near-Infrared and Radio Catalogs
    A&A 536, A102 (2011) Astronomy DOI: 10.1051/0004-6361/201116947 & c ESO 2011 Astrophysics Constructing a Galactic coordinate system based on near-infrared and radio catalogs J.-C. Liu1,2,Z.Zhu1,2, and B. Hu3,4 1 Department of astronomy, Nanjing University, Nanjing 210093, PR China e-mail: [jcliu;zhuzi]@nju.edu.cn 2 key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China 3 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China 4 Graduate School of Chinese Academy of Sciences, Beijing 100049, PR China e-mail: [email protected] Received 24 March 2011 / Accepted 13 October 2011 ABSTRACT Context. The definition of the Galactic coordinate system was announced by the IAU Sub-Commission 33b on behalf of the IAU in 1958. An unrigorous transformation was adopted by the Hipparcos group to transform the Galactic coordinate system from the FK4-based B1950.0 system to the FK5-based J2000.0 system or to the International Celestial Reference System (ICRS). For more than 50 years, the definition of the Galactic coordinate system has remained unchanged from this IAU1958 version. On the basis of deep and all-sky catalogs, the position of the Galactic plane can be revised and updated definitions of the Galactic coordinate systems can be proposed. Aims. We re-determine the position of the Galactic plane based on modern large catalogs, such as the Two-Micron All-Sky Survey (2MASS) and the SPECFIND v2.0. This paper also aims to propose a possible definition of the optimal Galactic coordinate system by adopting the ICRS position of the Sgr A* at the Galactic center.
    [Show full text]
  • Lecture 6: Galaxy Dynamics (Basic) Elliptical Galaxy Dynamics
    Lecture 6: Galaxy Dynamics (Basic) • Basic dynamics of galaxies – Ellipticals, kinematically hot random orbit systems – Spirals, kinematically cool rotating system • Key relations: – The fundamental plane of ellipticals/bulges – The Faber-Jackson relation for ellipticals/bulges – The Tully-Fisher for spirals disks • Using FJ and TF to calculate distances – The extragalactic distance ladder – Examples 1 Elliptical galaxy dynamics • Ellipticals are triaxial spheroids • No rotation, no flattened plane • Typically we can measure a velocity dispersion, σ – I.e., the integrated motions of the stars • Dynamics analogous to a gravitational bound cloud of gas (I.e., an isothermal sphere). • I.e., dp GM(r)ρ(r) HYDROSTATIC − = EQUILIBRIUM dr r2 Check Wikipedia “Hydrostatic PRESSURE FORCE GRAVITATIONAL FORCE Equilibrium” to see PER UNIT VOLUME PER UNIT VOLUME deriiation. € 2 1 Elliptical galaxy dynamics • For an isothermal sphere gas pressure is given by: 2 Reminder from p = ρ(r)σ Thermodynamics: P=nRT/V=ρT, 1 E=(3/2)kT=(1/2)mv^2 ρ(r) ∝ r2 σ 2 GM(r) 2 ⇒ 3 ∝ 4 2σ r r r M(r) = G M(r) ∝σ 2r € 3 € Elliptical galaxy dynamics • As E/S0s are centrally concentrated if σ is measured over sufficient area M(r)=>M, I.e., Total Mass ∝σ 2r • σ is measured from either: – Radial velocity distributions from individual stellar spectra – From line widths€ in integrated galaxy spectra [See Galactic Astronomy, Binney & Merrifield for details on how these are measured in practice] 4 2 Elliptical galaxy dynamices • We have three measureable quantities: – L = luminosity (or magnitude) – Re = effective or half-light radius – σ = velocity dispersion • From these we can derive Σο the central surface brightness (nb: one of these four is redundant as its calculable from the others.) • How are these related observationally and theoretically ? x y • I.e., what does: L ∝ Σ o σ ν look like ? Σο Log logL THE FUNDAMENTAL PLANE € Logσ 5 Fundamental Plane Theory 2 (I.e., stars behaving as if isothermal sphere) IF σν ∝ M Re 2 Surf.
    [Show full text]
  • Isolated Elliptical Galaxies in the Local Universe
    A&A 588, A79 (2016) Astronomy DOI: 10.1051/0004-6361/201527844 & c ESO 2016 Astrophysics Isolated elliptical galaxies in the local Universe I. Lacerna1,2,3, H. M. Hernández-Toledo4 , V. Avila-Reese4, J. Abonza-Sane4, and A. del Olmo5 1 Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. V. Mackenna 4860, Santiago, Chile e-mail: [email protected] 2 Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile, Av. V. Mackenna 4860, Santiago, Chile 3 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany 4 Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510 México D. F., Mexico 5 Instituto de Astrofísica de Andalucía IAA – CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain Received 26 November 2015 / Accepted 6 January 2016 ABSTRACT Context. We have studied a sample of 89 very isolated, elliptical galaxies at z < 0.08 and compared their properties with elliptical galaxies located in a high-density environment such as the Coma supercluster. Aims. Our aim is to probe the role of environment on the morphological transformation and quenching of elliptical galaxies as a function of mass. In addition, we elucidate the nature of a particular set of blue and star-forming isolated ellipticals identified here. Methods. We studied physical properties of ellipticals, such as color, specific star formation rate, galaxy size, and stellar age, as a function of stellar mass and environment based on SDSS data. We analyzed the blue and star-forming isolated ellipticals in more detail, through photometric characterization using GALFIT, and infer their star formation history using STARLIGHT.
    [Show full text]
  • Spatial Distribution of Galactic Globular Clusters: Distance Uncertainties and Dynamical Effects
    Juliana Crestani Ribeiro de Souza Spatial Distribution of Galactic Globular Clusters: Distance Uncertainties and Dynamical Effects Porto Alegre 2017 Juliana Crestani Ribeiro de Souza Spatial Distribution of Galactic Globular Clusters: Distance Uncertainties and Dynamical Effects Dissertação elaborada sob orientação do Prof. Dr. Eduardo Luis Damiani Bica, co- orientação do Prof. Dr. Charles José Bon- ato e apresentada ao Instituto de Física da Universidade Federal do Rio Grande do Sul em preenchimento do requisito par- cial para obtenção do título de Mestre em Física. Porto Alegre 2017 Acknowledgements To my parents, who supported me and made this possible, in a time and place where being in a university was just a distant dream. To my dearest friends Elisabeth, Robert, Augusto, and Natália - who so many times helped me go from "I give up" to "I’ll try once more". To my cats Kira, Fen, and Demi - who lazily join me in bed at the end of the day, and make everything worthwhile. "But, first of all, it will be necessary to explain what is our idea of a cluster of stars, and by what means we have obtained it. For an instance, I shall take the phenomenon which presents itself in many clusters: It is that of a number of lucid spots, of equal lustre, scattered over a circular space, in such a manner as to appear gradually more compressed towards the middle; and which compression, in the clusters to which I allude, is generally carried so far, as, by imperceptible degrees, to end in a luminous center, of a resolvable blaze of light." William Herschel, 1789 Abstract We provide a sample of 170 Galactic Globular Clusters (GCs) and analyse its spatial distribution properties.
    [Show full text]
  • Modeling and Interpretation of the Ultraviolet Spectral Energy Distributions of Primeval Galaxies
    Ecole´ Doctorale d'Astronomie et Astrophysique d'^Ile-de-France UNIVERSITE´ PARIS VI - PIERRE & MARIE CURIE DOCTORATE THESIS to obtain the title of Doctor of the University of Pierre & Marie Curie in Astrophysics Presented by Alba Vidal Garc´ıa Modeling and interpretation of the ultraviolet spectral energy distributions of primeval galaxies Thesis Advisor: St´ephane Charlot prepared at Institut d'Astrophysique de Paris, CNRS (UMR 7095), Universit´ePierre & Marie Curie (Paris VI) with financial support from the European Research Council grant `ERC NEOGAL' Composition of the jury Reviewers: Alessandro Bressan - SISSA, Trieste, Italy Rosa Gonzalez´ Delgado - IAA (CSIC), Granada, Spain Advisor: St´ephane Charlot - IAP, Paris, France President: Patrick Boisse´ - IAP, Paris, France Examinators: Jeremy Blaizot - CRAL, Observatoire de Lyon, France Vianney Lebouteiller - CEA, Saclay, France Dedicatoria v Contents Abstract vii R´esum´e ix 1 Introduction 3 1.1 Historical context . .4 1.2 Early epochs of the Universe . .5 1.3 Galaxytypes ......................................6 1.4 Components of a Galaxy . .8 1.4.1 Classification of stars . .9 1.4.2 The ISM: components and phases . .9 1.4.3 Physical processes in the ISM . 12 1.5 Chemical content of a galaxy . 17 1.6 Galaxy spectral energy distributions . 17 1.7 Future observing facilities . 19 1.8 Outline ......................................... 20 2 Modeling spectral energy distributions of galaxies 23 2.1 Stellar emission . 24 2.1.1 Stellar population synthesis codes . 24 2.1.2 Evolutionary tracks . 25 2.1.3 IMF . 29 2.1.4 Stellar spectral libraries . 30 2.2 Absorption and emission in the ISM . 31 2.2.1 Photoionization code: CLOUDY .......................
    [Show full text]
  • 2) Adolgov-PACTS.Pdf
    Primordial black holes, dark matter, and other cosmological puzzles A. D. Dolgov Novosibirsk State University, Novosibirsk, Russia ITEP, Moscow, Russia Particle, Astroparticle, and Cosmology Tallinn Symposium Tallinn, Estonia, June 18-22 2018 A. D. Dolgov PBH, DM, and other cosmological puzzles 19 June 2018 1 / 39 Recent astronomical data, which keep on appearing almost every day, show that the contemporary, z ∼ 0, and early, z ∼ 10, universe is much more abundantly populated by all kind of black holes, than it was expected even a few years ago. They may make a considerable or even 100% contribution to the cosmological dark matter. Among these BH: massive, M ∼ (7 − 8)M , 6 9 supermassive, M ∼ (10 − 10 )M , 3 5 intermediate mass M ∼ (10 − 10 )M , and a lot between and out of the intervals. Most natural is to assume that these black holes are primordial, PBH. Existence of such primordial black holes was essentially predicted a quarter of century ago (A.D. and J.Silk, 1993). A. D. Dolgov PBH, DM, and other cosmological puzzles 19 June 2018 2 / 39 However, this interpretation encounters natural resistance from the astronomical establishment. Sometimes the authors of new discoveries admitted that the observed phenomenon can be the explained by massive BHs, which drove the effect, but immediately retreated, saying that there was no known way to create sufficiently large density of such BHs. A. D. Dolgov PBH, DM, and other cosmological puzzles 19 June 2018 3 / 39 Astrophysical BH versus PBH Astrophysical BHs are results of stellar collapce after a star exhausted its nuclear fuel.
    [Show full text]
  • Star Formation in Ring Galaxies Susan C
    East Tennessee State University Digital Commons @ East Tennessee State University Undergraduate Honors Theses Student Works 5-2016 Star Formation in Ring Galaxies Susan C. Olmsted East Tennessee State Universtiy Follow this and additional works at: https://dc.etsu.edu/honors Part of the Astrophysics and Astronomy Commons, and the Physics Commons Recommended Citation Olmsted, Susan C., "Star Formation in Ring Galaxies" (2016). Undergraduate Honors Theses. Paper 322. https://dc.etsu.edu/honors/ 322 This Honors Thesis - Open Access is brought to you for free and open access by the Student Works at Digital Commons @ East Tennessee State University. It has been accepted for inclusion in Undergraduate Honors Theses by an authorized administrator of Digital Commons @ East Tennessee State University. For more information, please contact [email protected]. Star Formation in Ring Galaxies Susan Olmsted Honors Thesis May 5, 2016 Student: Susan Olmsted: ______________________________________ Mentor: Dr. Beverly Smith: ____________________________________ Reader 1: Dr. Mark Giroux: ____________________________________ Reader 2: Dr. Michele Joyner: __________________________________ 1 Abstract: Ring galaxies are specific types of interacting galaxies in which a smaller galaxy has passed through the center of the disk of another larger galaxy. The intrusion of the smaller galaxy causes the structure of the larger galaxy to compress as the smaller galaxy falls through, and to recoil back after the smaller galaxy passes through, hence the ring-like shape. In our research, we studied the star-forming regions of a sample of ring galaxies and compared to those of other interacting galaxies and normal galaxies. Using UV, optical, and IR archived images in twelve wavelengths from three telescopes, we analyzed samples of star-forming regions in ring and normal spiral galaxies using photometry.
    [Show full text]
  • And Ecclesiastical Cosmology
    GSJ: VOLUME 6, ISSUE 3, MARCH 2018 101 GSJ: Volume 6, Issue 3, March 2018, Online: ISSN 2320-9186 www.globalscientificjournal.com DEMOLITION HUBBLE'S LAW, BIG BANG THE BASIS OF "MODERN" AND ECCLESIASTICAL COSMOLOGY Author: Weitter Duckss (Slavko Sedic) Zadar Croatia Pусскй Croatian „If two objects are represented by ball bearings and space-time by the stretching of a rubber sheet, the Doppler effect is caused by the rolling of ball bearings over the rubber sheet in order to achieve a particular motion. A cosmological red shift occurs when ball bearings get stuck on the sheet, which is stretched.“ Wikipedia OK, let's check that on our local group of galaxies (the table from my article „Where did the blue spectral shift inside the universe come from?“) galaxies, local groups Redshift km/s Blueshift km/s Sextans B (4.44 ± 0.23 Mly) 300 ± 0 Sextans A 324 ± 2 NGC 3109 403 ± 1 Tucana Dwarf 130 ± ? Leo I 285 ± 2 NGC 6822 -57 ± 2 Andromeda Galaxy -301 ± 1 Leo II (about 690,000 ly) 79 ± 1 Phoenix Dwarf 60 ± 30 SagDIG -79 ± 1 Aquarius Dwarf -141 ± 2 Wolf–Lundmark–Melotte -122 ± 2 Pisces Dwarf -287 ± 0 Antlia Dwarf 362 ± 0 Leo A 0.000067 (z) Pegasus Dwarf Spheroidal -354 ± 3 IC 10 -348 ± 1 NGC 185 -202 ± 3 Canes Venatici I ~ 31 GSJ© 2018 www.globalscientificjournal.com GSJ: VOLUME 6, ISSUE 3, MARCH 2018 102 Andromeda III -351 ± 9 Andromeda II -188 ± 3 Triangulum Galaxy -179 ± 3 Messier 110 -241 ± 3 NGC 147 (2.53 ± 0.11 Mly) -193 ± 3 Small Magellanic Cloud 0.000527 Large Magellanic Cloud - - M32 -200 ± 6 NGC 205 -241 ± 3 IC 1613 -234 ± 1 Carina Dwarf 230 ± 60 Sextans Dwarf 224 ± 2 Ursa Minor Dwarf (200 ± 30 kly) -247 ± 1 Draco Dwarf -292 ± 21 Cassiopeia Dwarf -307 ± 2 Ursa Major II Dwarf - 116 Leo IV 130 Leo V ( 585 kly) 173 Leo T -60 Bootes II -120 Pegasus Dwarf -183 ± 0 Sculptor Dwarf 110 ± 1 Etc.
    [Show full text]
  • 12 Strong Gravitational Lenses
    12 Strong Gravitational Lenses Phil Marshall, MaruˇsaBradaˇc,George Chartas, Gregory Dobler, Ard´ısEl´ıasd´ottir,´ Emilio Falco, Chris Fassnacht, James Jee, Charles Keeton, Masamune Oguri, Anthony Tyson LSST will contain more strong gravitational lensing events than any other survey preceding it, and will monitor them all at a cadence of a few days to a few weeks. Concurrent space-based optical or perhaps ground-based surveys may provide higher resolution imaging: the biggest advances in strong lensing science made with LSST will be in those areas that benefit most from the large volume and the high accuracy, multi-filter time series. In this chapter we propose an array of science projects that fit this bill. We first provide a brief introduction to the basic physics of gravitational lensing, focusing on the formation of multiple images: the strong lensing regime. Further description of lensing phenomena will be provided as they arise throughout the chapter. We then make some predictions for the properties of samples of lenses of various kinds we can expect to discover with LSST: their numbers and distributions in redshift, image separation, and so on. This is important, since the principal step forward provided by LSST will be one of lens sample size, and the extent to which new lensing science projects will be enabled depends very much on the samples generated. From § 12.3 onwards we introduce the proposed LSST science projects. This is by no means an exhaustive list, but should serve as a good starting point for investigators looking to exploit the strong lensing phenomenon with LSST.
    [Show full text]
  • An Introduction to Our Universe
    An Introduction to Our Universe Lyman Page Princeton, NJ [email protected] Draft, August 31, 2018 The full-sky heat map of the temperature differences in the remnant light from the birth of the universe. From the bluest to the reddest corresponds to a temperature difference of 400 millionths of a degree Celsius. The goal of this essay is to explain this image and what it tells us about the universe. 1 Contents 1 Preface 2 2 Introduction to Cosmology 3 3 How Big is the Universe? 4 4 The Universe is Expanding 10 5 The Age of the Universe is Finite 15 6 The Observable Universe 17 7 The Universe is Infinite ?! 17 8 Telescopes are Like Time Machines 18 9 The CMB 20 10 Dark Matter 23 11 The Accelerating Universe 25 12 Structure Formation and the Cosmic Timeline 26 13 The CMB Anisotropy 29 14 How Do We Measure the CMB? 36 15 The Geometry of the Universe 40 16 Quantum Mechanics and the Seeds of Cosmic Structure Formation. 43 17 Pulling it all Together with the Standard Model of Cosmology 45 18 Frontiers 48 19 Endnote 49 A Appendix A: The Electromagnetic Spectrum 51 B Appendix B: Expanding Space 52 C Appendix C: Significant Events in the Cosmic Timeline 53 D Appendix D: Size and Age of the Observable Universe 54 1 1 Preface These pages are a brief introduction to modern cosmology. They were written for family and friends who at various times have asked what I work on. The goal is to convey a geometrical picture of how to think about the universe on the grandest scales.
    [Show full text]
  • Photometric Survey for Dwarf Galaxies Within Intergalactic Voids Rochelle
    Photometric Survey for Dwarf Galaxies Within Intergalactic Voids Rochelle Steele A senior thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Bachelor of Science J. Ward Moody, Advisor Department of Physics and Astronomy Brigham Young University April 2019 Copyright © 2019 Rochelle Steele All Rights Reserved ABSTRACT Photometric Survey for Dwarf Galaxies Within Intergalactic Voids Rochelle Steele Department of Physics and Astronomy, BYU Bachelor of Science No astronomer has yet discovered the dwarf galaxies that many L Cold Dark Matter (LCDM) simulations predict should be abundant within intergalactic voids. Spectroscopic observations are necessary to identify and determine the distances to these galaxies. However, dwarf galaxies are so faint that it is difficult to observe them with spectroscopic methods. We have developed a way to photometrically identify dwarf galaxies and estimate their distance using three narrowband filters centered on the Ha emission line. From this method, the redshift of the Ha emission line can be estimated, which gives the distance to the galaxy. Equivalent width, or strength, of the emission line detected can also be estimated. The line observed must be verified as Ha emission using observations with Sloan broadband filters. We have primarily studied one void, FN8, using these methods and have found 14 candidate dwarf galaxies, which must still be confirmed spectroscopically. The low density of candidate void galaxies rejects the hypothesis that there is a uniform distribution of dwarf galaxies within the void, as suggested by some LCDM simulations. Keywords: large-scale structure, voids, dwarf galaxies, dark matter, LCDM ACKNOWLEDGMENTS I would first like to thank my advisor, Dr.
    [Show full text]
  • Monthly Newsletter of the Durban Centre - March 2018
    Page 1 Monthly Newsletter of the Durban Centre - March 2018 Page 2 Table of Contents Chairman’s Chatter …...…………………….……….………..….…… 3 Andrew Gray …………………………………………...………………. 5 The Hyades Star Cluster …...………………………….…….……….. 6 At the Eye Piece …………………………………………….….…….... 9 The Cover Image - Antennae Nebula …….……………………….. 11 Galaxy - Part 2 ….………………………………..………………….... 13 Self-Taught Astronomer …………………………………..………… 21 The Month Ahead …..…………………...….…….……………..…… 24 Minutes of the Previous Meeting …………………………….……. 25 Public Viewing Roster …………………………….……….…..……. 26 Pre-loved Telescope Equipment …………………………...……… 28 ASSA Symposium 2018 ………………………...……….…......…… 29 Member Submissions Disclaimer: The views expressed in ‘nDaba are solely those of the writer and are not necessarily the views of the Durban Centre, nor the Editor. All images and content is the work of the respective copyright owner Page 3 Chairman’s Chatter By Mike Hadlow Dear Members, The third month of the year is upon us and already the viewing conditions have been more favourable over the last few nights. Let’s hope it continues and we have clear skies and good viewing for the next five or six months. Our February meeting was well attended, with our main speaker being Dr Matt Hilton from the Astrophysics and Cosmology Research Unit at UKZN who gave us an excellent presentation on gravity waves. We really have to be thankful to Dr Hilton from ACRU UKZN for giving us his time to give us presentations and hope that we can maintain our relationship with ACRU and that we can draw other speakers from his colleagues and other research students! Thanks must also go to Debbie Abel and Piet Strauss for their monthly presentations on NASA and the sky for the following month, respectively.
    [Show full text]