DOCSLIB.ORG

The “Ugly Duckling”, in the Realm of the Galaxies

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The “Ugly Duckling”, in the Realm of the Galaxies The \ugly duckling", in the realm of the galaxies Domingos Soares The galaxies that most call our attention to are the spiral galaxies | es- pecially because of the beauty of the spiral arms | and the elliptical galaxies, which present an uniform and smooth light distribution against the sky back- ground. There is, though, a type of galaxy, whose attractiveness is precisely the fact of not presenting harmony or regularity on its shape. It is the \ugly duckling" of the realm of the galaxies, and the representatives of that type are called very appropriately \irregular galaxies". Irregular galaxies tend to be smaller than spirals and ellipticals and are even called \dwarf" galaxies. Actually, the term \irregular galaxy" is applied both to dwarf spiral galaxies, with disturbed structure, as our companion, the Large Magellanic Cloud, and to all other galaxies that do not fit on any of the types that have a regular structure. Incidentally, the Magellanic Clouds | the Large and the Small | are satellite galaxies of our Milky Way, being easily seen with the naked eye on the southern hemisphere skies. They were discovered by the Portuguese navigator Ferdinand Magellan (1480-1521), in 1520, when he undertook his Earth's circumnavigation voyage. When Edwin Hubble (1889-1953) put forward his classification scheme of galaxies | known as Hubble's tuning fork |, he simply classified all galaxies that did not fit on the types spiral and elliptical as \irregular". Presently, irregular themselves have an internal classification distinction, as we shall see. Now, Hubble called \Irr I" the irregular galaxies in which he could discern at least some sign of a structure, for example, indications of a spiral arm. And called \Irr II" those which show an extremely disorganized appearance. For Hubble, therefore, both Magellanic Clouds, the Large and the Small, fit the Irr I category. The Large Magellanic Cloud presents a prominent stellar bar and indi- 1 cations of a spiral arm. The Small Magellanic Cloud presents an elongated structure with no signs of spiral arms whatsoever. Both are dwarf galaxies, i.e., their masses are thousands of times smaller than the mass of a typical spiral galaxy as ours. The Large Magellanic Cloud on left and the Small Magellanic Cloud. They are dwarf galaxies and satellites of the Milky Way. The Large Magellanic Cloud is the prototype of a subclass of irregular galaxies. Notice the stellar bar of the Large Cloud, which is the main structure seen in the image. The Large and the Small Magellanic Clouds were classified by Hubble as Irr I. The Small Cloud is likely a disk distorted by gravitational tidal forces (Images: LMC, Eckhard Slawik; SMC, David Malin). The classification of the irregulars used by Hubble revealed itself very broad, as long as more observations of irregular galaxies became available. There was clearly the need of further detailing in the definition of types of irregular galaxies. The French astronomer, based in the United States, G´erardde Vau- couleurs (1918-1995) was responsible for a great improvement of the Hubble system of galaxy classification. Among other contributions, he introduced a modification, in the case of irregulars, with the objective of having a more discriminating classification. He proposed that the irregulars were classified as an extension of the classification of spiral galaxies. Hubble defined the types Sa, Sb and Sc for the spirals. The bulges diminish and the spiral arms 2 open up, along the sequence a-b-c. A spiral galaxy Sa, for example, presents a large bulge and spiral arms very close to the bulge. Hence, de Vaucouleurs created the new type Sd, in which arms do exist but they start to show ir- regularities in their definition. Next, he created the type Sm | \m" as in Magellanic |, already in the domain of irregulars, in fact, substituting Hub- ble's Irr I, whose prototype, or model, was the Large Magellanic Cloud. He created yet the type Im, whose most illustrious representative is the Small Cloud, and finally created the type Ir, to include the truly irregulars, often also called \amorphous" galaxies, that is, literally galaxies \without a form". The latter would include Hubble's Irr II. We have then for spiral and irregular galaxies the new sequence Sa-Sb- Sc-Sd-Sm-Im-Ir. In practice, this corresponds to an extension of the branch of normal spirals on Hubble's tuning fork. Likewise, we have the extension SBa-SBb-SBc-SBd-SBm-Im-Ir for the branch of barred spiral galaxies on the original Hubble's classification. We can now reconsider the above figure, where we show the Magellanic Clouds. According to de Vaucouleurs' revision, they are now classified as SBm | the Large Cloud | and Im | the Small Cloud. Irregular galaxies are also many times observed at great distances from us. This is shown in the next figure, which presents some of the irregular galaxies observed by the Hubble Space Telescope, whose times of exposure were very long. 3 Distant irregular galaxies observed by the Hubble Space Telescope. From the galaxy at the upper left corner, and in the clockwise direction, they may be ten- tatively classified as SBm, Ir, Ir and Sd, in de Vaucouleurs' revised system. The blueish regions in the galaxies indicate regions of intense star formation, a typical feature of irregular galaxies (Images: Richard Griffiths, NASA/HST). Irregular galaxies have some characteristics which are exhibited in all subtypes, from Sd to Ir. In the first place, they have regions of intense star formation. Such regions show up in the images as zones of predominantly blue color. The blue color is emitted by young stars with masses much larger than the Sun mass | 5 to 10 times larger | and that evolve rapidly, existing for \only" tens of millions of years. Stars with masses equal or smaller than the Sun mass exist for up to tens of billions of years. Another characteristic, intimately related to star formation, is the presence of gas and dust clouds. These clouds are seen in the images with small reddish patches. The red light comes from the energetically excited gas hydrogen. Hydrogen is not the only 4 component of these clouds, but is the most abundant element. The hydrogen excitation is caused by the intense radiation from neighboring stars. These stars, besides blue light, strongly emit ultraviolet radiation, that is highly energetic, and ionize and energetically excite the gas present in the clouds. From the structural point of view, irregular galaxies present many times a stellar bulge | the spheroidal structure present in the central region of spiral galaxies. But the bulge, when present, is always displaced from the central region of the galaxy. This is a sign of morphological disturbance, a basic feature of irregular galaxies. Irregular galaxies are frequently the result of collisions of two or more galaxies, or of disturbances originated from strong tidal gravitational interactions with a nearby galaxy. Our next irregular, M82, was probably disturbed by its companion, the beautiful spiral M81. M82 is a Ir. It is called the \Cigar" galaxy, due to its global appearance on short time exposure observations. But when we examine its internal structure we verify that it is really a true Ir, with little order in the stellar distribution. On left, the pair of galaxies M81 and M82. M82 is seen beside in details. Notice the disturbed internal structure. The dark patches are dust clouds, which absorb visible light. The blueish color comes from the galaxy stars. The filamentary structure, perpendicular to the plane of the galaxy, is due to ionized hydrogen emitting its characteristic red light (Images: M81-M82, Takayuki Yoshida; M82, Subaru Telescope, Japan). To finalize, we made a homage to the Large Magellanic Cloud, our clos- est galaxy, and easily visible to the southern hemisphere observers. With the naked eye, it is seen as a whitish luminous patch against the night sky 5 background, resembling an usual cloud of meteorological nature. Such a confusion is frequent amongst the less informed. But it is a true galaxy! And, for the inhabitants of the southern hemisphere, having this vision is an extraordinary privilege. The image presented next was obtained with long time exposure and shows that the Large Cloud indeed resembles a barred spiral galaxy. The fragmented structure of the probable spiral arms leaves no doubt, nevertheless, about its true nature as an irregular galaxy. But this \ugly duckling" is very pretty, isn't it? Image of the Large Magellanic Cloud obtained with a long exposure time. Its classification as SBm is unquestionable. Notice the central bar and the fragmented spiral arms around it (Image: Yuri Beletsky, ESO). 6.
Load more

Recommended publications
  • A New View of Supernova Remnants in the L\:Fagellanic Clouds from David Clark
    690 Nature Vol. 294 24/31 December 1981 Finally, whatofTRF4? Aftermanyyears functions early (proliferative phase). The given by a current report describing a start of difficulty, created in part by the ability relationship to the newly described B cell on molecular biological studies of IL2. of factors like IL2 and the B cell growth growth factor awaits further experiments. Given several T cell tumour lines which can factor to replace T cells indirectly, assays In both cases, a clearer understanding of be induced to generate high levels of IL2 which clearly distinguish between IL2 and the roles of several lymphokines now (several thousand times the amounts pro­ TRF are now in hand. And the take-home exists, and perhaps more important, the duced by normal lymphocytes), it has been message is that, indeed, TRF exists12 • It tools and approaches necessary for more possible to follow the lead of workers in the acts at the time when B cells, having sophisticated analysis are evident. interferon field, by looking for mRNA undergone clonal expansion following An indication of future directions is coding for the lymphokine, and then antigenic stimulation, are to begin attempting to clone its complementary secreting high levels of immunoglobulin. I. OiSabato, G .• Chen, 0.-M. & Erickson . .1.W. Cell. DNA. The EL4 variant cell line originally Then, as proposed years ago by Dutton and lmmun. 17,495 (1975). described by Farrar and colleagues at 2. Gillis. S. & Smith, K.A. Nature 268, 154 (1977). 13 colleagues, TRF can replace T cells in ). Ruscetti, F.W., Morgan, D.A. & Gallo, R.C.
    [Show full text]
  • The Recent Star Formation in Sextans a Schuyler D
    THE ASTRONOMICAL JOURNAL, 116:2341È2362, 1998 November ( 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A. THE RECENT STAR FORMATION IN SEXTANS A SCHUYLER D. VAN DYK1 Infrared Processing and Analysis Center, California Institute of Technology, Mail Code 100-22, Pasadena, CA 91125; vandyk=ipac.caltech.edu DANIEL PUCHE1 Tellabs Transport Group, Inc., 3403 Griffith Street, Ville St. Laurent, Montreal, Quebec H4T 1W5, Canada; Daniel.Puche=tellabs.com AND TONY WONG1 Department of Astronomy, University of California at Berkeley, 601 Cambell Hall, Berkeley, CA 94720-3411; twong=astro.berkeley.edu Received 5 February 1998; revised 1998 July 8 ABSTRACT We investigate the relationship between the spatial distributions of stellar populations and of neutral and ionized gas in the Local Group dwarf irregular galaxy Sextans A. This galaxy is currently experi- encing a burst of localized star formation, the trigger of which is unknown. We have resolved various populations of stars via deepUBV (RI) imaging over an area with [email protected]. We have compared our photometry with theoretical isochronesC appropriate for Sextans A, in order to determine the ages of these populations. We have mapped out the history of star formation, most accurately for times [100 Myr. We Ðnd that star formation in Sextans A is correlated both in time and space, especially for the most recent([12 Myr) times. The youngest stars in the galaxy are forming primarily along the inner edge of the large H I shell. Somewhat older populations,[50 Myr, are found inward of the youngest stars. Progressively older star formation, from D50È100 Myr, appears to have some spatially coherent structure and is more centrally concentrated.
    [Show full text]
  • Large Magellanic Cloud, One of Our Busy Galactic Neighbors
    The Large Magellanic Cloud, One of Our Busy Galactic Neighbors www.nasa.gov Our Busy Galactic Neighbors also contain fewer metals or elements heavier than hydrogen and helium. Such an environment is thought to slow the growth The cold dust that builds blazing stars is revealed in this image of stars. Star formation in the universe peaked around 10 billion that combines infrared observations from the European Space years ago, even though galaxies contained lesser abundances Agency’s Herschel Space Observatory and NASA’s Spitzer of metallic dust. Previously, astronomers only had a general Space Telescope. The image maps the dust in the galaxy known sense of the rate of star formation in the Magellanic Clouds, as the Large Magellanic Cloud, which, with the Small Magellanic but the new images enable them to study the process in more Cloud, are the two closest sizable neighbors to our own Milky detail. Way Galaxy. Herschel is a European The Large Magellanic Cloud looks like a fiery, circular explosion Space Agency in the combined Herschel–Spitzer infrared data. Ribbons of dust cornerstone mission, ripple through the galaxy, with significant fields of star formation with science instruments noticeable in the center, center-left and top right. The brightest provided by consortia center-left region is called 30 Doradus, or the Tarantula Nebula, of European institutes for its appearance in visible light. and with important participation by NASA. NASA’s Herschel Project Office is based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. JPL contributed mission-enabling technology for two of Herschel’s three science instruments.
    [Show full text]
  • NASA Teacher Science Background Q&A
    National Aeronautics and Space Administration Science Teacher’s Background SciGALAXY Q&As NASA / Amazing Space Science Background: Galaxy Q&As 1. What is a galaxy? A galaxy is an enormous collection of a few million to several trillion stars, gas, and dust held together by gravity. Galaxies can be several thousand to hundreds of thousands of light-years across. 2. What is the name of our galaxy? The name of our galaxy is the Milky Way. Our Sun and all of the stars that you see at night belong to the Milky Way. When you go outside in the country on a dark night and look up, you will see a milky, misty-looking band stretching across the sky. When you look at this band, you are looking into the densest parts of the Milky Way — the “disk” and the “bulge.” The Milky Way is a spiral galaxy. (See Q7 for more on spiral galaxies.) 3. Where is Earth in the Milky Way galaxy? Our solar system is in one of the spiral arms of the Milky Way, called the Orion Arm, and is about two-thirds of the way from the center of the galaxy to the edge of the galaxy’s starlight. Earth is the third planet from the Sun in our solar system of eight planets. 4. What is the closest galaxy that is similar to our own galaxy, and how far away is it? The closest spiral galaxy is Andromeda, a galaxy much like our own Milky Way. It is 2. million light-years away from us.
    [Show full text]
  • E+FW Abstract Book
    Elizabeth and Frederick White Conference on the Magellanic System SCIENTIFIC ORGANISING COMMITTEE Dr. Erik Muller ATNF, CSIRO Dr. Bärbel Koribalski ATNF, CSIRO Prof. Yasuo Fukui University of Nagoya Dr. Russell Cannon Anglo-Australian Observatory Prof. Lister Staveley-Smith Univeristy of Western Australia Dr. Kenji Bekki University of New South Wales LOCAL ORGANISING COMMITTEE Dr. Erik Muller ATNF, CSIRO Deanna Matthews La Trobe University / ATNF, CSIRO Vicki Fraser ATNF, CSIRO Miroslav Filipovic University of Western Sydney Elizabeth and Frederick White Conference on the Magellanic System PARTICIPANT LIST Bekki Kenji Univeristy of New South Wales Besla Gurtina Harvard-Smithsonian CfA Bland-Hawthorn Joss Anglo-Australian Observatory Bolatto Alberto UCB Bot Caroline California Institute of Technology Braun Robert Australia Telescope National Facility Brooks Kate Australia Telescope National Facility Cannon Russell Anglo-Australian Observatory Carlson Lynn Johns Hopkins University Cioni Maria-Rosa Institute for Astronomy, University of Edinburgh Da Costa Gary Research School of Astronomy & Astrophysics ANU Doi Yasuo University of Tokyo Ekers Ron Australia Telescope National Facility Filipovic Miroslav University of Western Sydney Fukui Yasuo Nagoya University Gaensler Bryan University of Sydney Harris Jason Steward Observatory Hitschfeld Marc University of Colgne Hughes Annie Centre for Astrophysics & Supercomputing, Swinburne University Hurley Jarrod Centre for Astrophysics & Supercomputing, Swinburne University Francisco Ibarra Javier
    [Show full text]
  • Galactic and Extragalactic Studies, Xxiii. Opacity of the Southern Milky Way Dust Clouds by Harlow Shapley and Jacqueline Sweeney
    GALACTIC AND EXTRAGALACTIC STUDIES, XXIII. OPACITY OF THE SOUTHERN MILKY WAY DUST CLOUDS BY HARLOW SHAPLEY AND JACQUELINE SWEENEY HARVARD COLLEGE OBSERVATORY Communicated June 3, 1955 The greater richness of the southern celestial hemisphere when compared with the northern is illustrated by its brightest constellations, Scorpius, Sagittarius, Centaurus, and Crux, and in such stellar giants of brightness and size as Sirius, Antares, Canopus, and Achernar. It is the hemisphere of the nearest external galaxies (the Magellanic Clouds) and of the central nucleus of our Milky Way. A consequence of the latter is that more than four-fifths of the known globular star clusters, including the two brightest, Omega Centauri and 47 Tucanae, are also southern, as is the heavily obscured Messier 4, probably the nearest of all globular clusters. But perhaps the most outstanding features of the southern sky are the brilliance of the gaseous nebulosities in Orion, Carina, and Sagittarius and the darkness of the large obscurations among the Milky Way star clouds, especially the darkness of the Coalsack and of the complex of obscurities around Rho Ophi- uchi. An examination of the opacity of these discrete dark nebulosities, and of the general cosmic dust that obscures the distant parts of the southern Milky Way, is reported in this communication. 1. On the basis of galaxy counts on photographs made with the Mount Wilson reflectors, E. P. Hubble published in 1934 his well-known picture of the distribution of faint galaxies. He was able to take his sampling survey southward only to dec- lination -30°. Hubble's work on northern galaxies is now being reinforced, or actually supplanted, by the full-coverage atlas of the northern sky by C.
    [Show full text]
  • Lesson 5 Galaxies and Beyond
    LESSON 5 GALAXIES AND BEYOND Chapter 8 Astronomy OBJECTIVES • Classify galaxies according to their properties. • Explain the big bang and the way in which Earth and its atmosphere were formed. MAIN IDEA The Milky Way is one of billions of galaxies that are moving away from each other in an expanding universe. VOCABULARY • galaxy • Milky Way • spectrum • expansion redshift • big bang • background radiation WHAT ARE GALAXIES? • A galaxy is a group of star clusters held together by gravity. • Stars move around the center of their galaxy in the same way that planets orbit a star. • Galaxies differ in size, age, and structure. • Astronomers place them in three main groups based on shape. • spiral • elliptical • irregular SPIRAL GALAXY • Spiral galaxies look like whirlpools. • Some are barred spiral galaxies. • Have bars of stars, gas, and dust throughout its center. • Spiral arms emerge from this bar. ELLIPTICAL GALAXY • An elliptical galaxy is shaped a bit like a football. • It has no spiral arms and little or no dust. IRREGULAR GALAXY • Has no recognizable shape. • The amount of dust varies. • Collisions with other galaxies may have caused the irregular shape. THE MILKY WAY GALAXY • During the summer at night, overhead, you will see a broad band of light stretching across the sky. • You are looking at part of the Milky Way. • The Milky Way is our home galaxy. • The Milky Way is a spiral galaxy. • The stars are grouped in a bulge around a core. • All of the stars in the Milky Way including our sun orbit this core. • The closer a star is to the core the faster its orbit.
    [Show full text]
  • A Synoptic View of the Magellanic Clouds: VMC, Gaia, and Beyond Held at ESO Headquarters, Garching, Germany, 9–13 September 2019
    Astronomical News DOI: 10.18727/0722-6691/5211 Report on the ESO Workshop A Synoptic View of the Magellanic Clouds: VMC, Gaia, and Beyond held at ESO Headquarters, Garching, Germany, 9–13 September 2019 Maria-Rosa L. Cioni 1 In this workshop, the most interesting of the system and use stellar population Martino Romaniello 2 discoveries emerging from the VMC and diagnostics across the Hertzsprung- Richard I. Anderson 2 other contemporary multi-wavelength Russell diagram with unprecedented pre- surveys were discussed. These results cision. Most of these developments will have cemented stellar populations as culminate in the early 2020s and discus- 1 Leibniz-Institut für Astrophysik Potsdam important diagnostics of galaxy proper- sions on how to formulate the most rele- (AIP), Germany ties. Cepheid stars have, for example, vant scientific questions are already 2 ESO revealed the three-dimensional structure advanced. of the system, giant stars have shown significantly extended populations, and The year 2019 marked the quincente- blue horizontal branch stars have indi- Summaries of talks and highlights from nary of the arrival in the southern hemi- cated protuberances and possible sessions sphere of Ferdinand Magellan, the streams in the outskirts of the galaxies. namesake of the Magellanic Clouds, The complementary view provided by The workshop revolved around eight our nearest example of dwarf galaxies RR Lyrae stars shows instead regular and scientific sessions at which a total of in the early stages of a minor merging ellipsoidal systems. The analysis of the 64 talks were presented and a summary event. These galaxies have been firmly star formation history suggests that the is given below.
    [Show full text]
  • Galaxies Galore Worksheets
    http://amazing-space.stsci.edu/resources/explorations/galaxies-galore/ Name: _______________________________________________________________ Background: How Are Galaxies Classified? What Do They Look Like? Edwin Hubble classified galaxies into four major types: spiral, barred spiral, elliptical, and irregular. Most galaxies are spirals, barred spirals, or ellipticals. Spiral galaxies are made up of a flattened disk containing spiral (pinwheel-shaped) arms, a bulge at its center, and a halo. Spiral galaxies have a variety of shapes and are classified according to the size of the bulge and the tightness and appearance of the arms. The spiral arms, which wrap around the bulge, contain numerous young blue stars and lots of gas and dust. Stars in the bulge tend to be older and redder. Yellow stars like our Sun are found throughout the disk of a spiral galaxy. These galaxies rotate somewhat like a hurricane or a whirlpool. Barred spiral galaxies are spirals that have a bar running across the center of the galaxy. Elliptical galaxies do not have a disk or arms. Instead, they are characterized by a smooth, ball-shaped appearance. Ellipticals contain old stars, and possess little gas or dust. They are classified by the shape of the ball, which can range from round to oval (baseball-shaped to football-shaped). The smallest elliptical galaxies (called "dwarf ellipticals") are probably the most common type of galaxy in the nearby universe. In contrast to spirals, the stars in ellipticals do not revolve around the center in an organized way. The stars move on randomly oriented orbits within the galaxy like a swarm of bees.
    [Show full text]
  • The Magellanic Stream As a Probe of Astrophysics
    Astro2020 Science White Paper The Magellanic Stream as a Probe of Astrophysics Thematic Areas: ☐ Planetary Systems ☐ Star and Planet Formation ☐Formation and Evolution of Compact Objects ☐ Cosmology and Fundamental Physics ☐Stars and Stellar Evolution ☐Resolved Stellar Populations and their Environments ☒Galaxy Evolution ☐Multi-Messenger Astronomy and Astrophysics Principal Author: Andrew J Fox, Space Telescope Science Institute, [email protected], 410 338 5083 Co-authors: Kathleen A. Barger, Texas Christian University, [email protected] Joss Bland-Hawthorn, University of Sydney, [email protected] Dana Casetti-Dinescu, Southern Connecticut State University, [email protected] Elena d’Onghia, University of Wisconsin-Madison, [email protected] Felix J. Lockman, Green Bank Observatory, [email protected] Naomi McClure-Griffiths, Australian National University, [email protected] David Nidever, University of Montana, [email protected] Mary Putman, Columbia University, [email protected] Philipp Richter, University of Potsdam, [email protected] Snezana Stanimirovic, University of Wisconsin-Madison, [email protected] Thorsten Tepper-Garcia, University of Sydney, [email protected] Abstract: Extending for over 200 degrees across the sky, the Magellanic Stream together with its Leading Arm is the most spectacular example of a gaseous stream in the local Universe. The Stream is an interwoven tail of filaments trailing the Magellanic Clouds as they orbit the Milky Way. Thought to be created by tidal forces, ram pressure, and halo interactions, the Stream is a benchmark for dynamical models of the Magellanic System, a case study for gas accretion and dwarf-galaxy accretion onto galaxies, a probe of the outer halo, and the bearer of more gas mass than all other Galactic high velocity clouds combined.
    [Show full text]
  • Annual Report 2013 E.Indd
    2013 ANNUAL REPORT NATIONAL RADIO ASTRONOMY OBSERVATORY 1 NRAO SCIENCE NRAO SCIENCE NRAO SCIENCE NRAO SCIENCE NRAO SCIENCE NRAO SCIENCE NRAO SCIENCE 493 EMPLOYEES 40 PRESS RELEASES 462 REFEREED SCIENCE PUBLICATIONS NRAO OPERATIONS $56.5 M 2,100+ ALMA OPERATIONS SCIENTIFIC USERS $31.7 M ALMA CONSTRUCTION $11.9 M EVLA CONSTRUCTION A SUITE OF FOUR WORLDCLASS $0.7 M ASTRONOMICAL OBSERVATORIES EXTERNAL GRANTS $3.8 M NRAO FACTS & FIGURES $ 2 Contents DIRECTOR’S REPORT. 5 NRAO IN BRIEF . 6 SCIENCE HIGHLIGHTS . 8 ALMA CONSTRUCTION. 26 OPERATIONS & DEVELOPMENT . 30 SCIENCE SUPPORT & RESEARCH . 58 TECHNOLOGY . 74 EDUCATION & PUBLIC OUTREACH. 80 MANAGEMENT TEAM & ORGANIZATION. 84 PERFORMANCE METRICS . 90 APPENDICES A. PUBLICATIONS . 94 B. EVENTS & MILESTONES . 118 C. ADVISORY COMMITTEES . .120 D. FINANCIAL SUMMARY . .124 E. MEDIA RELEASES . .126 F. ACRONYMS . .136 COVER: The National Radio Astronomy Observatory Karl G. Jansky Very Large Array, located near Socorro, New Mexico, is a radio telescope of unprecedented sensitivity, frequency coverage, and imaging capability that was created by extensively modernizing the original Very Large Array that was dedicated in 1980. This major upgrade was completed on schedule and within budget in December 2012, and the Jansky Very Large Array entered full science operations in January 2013. The upgrade project was funded by the US National Science Foundation, with additional contributions from the National Research Council in Canada, and the Consejo Nacional de Ciencia y Tecnologia in Mexico. Credit: NRAO/AUI/NSF. LEFT: An international partnership between North America, Europe, East Asia, and the Republic of Chile, the Atacama Large Millimeter/submillimeter Array (ALMA) is the largest and highest priority project for the National Radio Astronomy Observatory, its parent organization, Associated Universities, Inc., and the National Science Foundation – Division of Astronomical Sciences.
    [Show full text]
  • A Unified Formation Scenario for the Zoo of Extended Star Clustersand Ultra-Compact Dwarf Galaxies
    A UNIFIED FORMATION SCENARIO FOR THE ZOO OF EXTENDED STAR CLUSTERS AND ULTRA-COMPACT DWARF GALAXIES DISSERTATION zur Erlangung des Doktorgrades (Dr. rer. nat.) der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn vorgelegt von RENATE CLAUDIA BRÜNS aus Bonn Bonn, 2013 Angefertigt mit Genehmigung der Mathematisch-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn 1. Gutachter: Prof. Dr. P. Kroupa 2. Gutachter: Prof. Dr. U. Klein Tag der Promotion: 16. Juni 2014 Erscheinungsjahr: 2014 Contents Abstract 1 1 Introduction 3 1.1 Old Star Clusters in the Local Group ......................... 3 1.2 Old Star Clusters beyond the Local Group ..................... 7 1.3 Ultra-Compact Dwarf Galaxies ............................ 8 1.4 Young Massive Star Clusters and Star Cluster Complexes ............. 9 1.5 Outline of Thesis .................................... 14 2 NumericalMethod 17 2.1 N-BodyCodes ..................................... 17 2.1.1 Set-Up of the Initial Conditions ....................... 18 2.1.2 The Integrator ................................. 22 2.1.3 Determination of Accelerations from the N Particles ............ 23 2.1.4 The Analytical External Tidal Field ..................... 26 2.1.5 Determination of the Enclosed Mass and the Effective Radius ...... 29 2.2 The Particle-Mesh Code SUPERBOX ......................... 29 2.2.1 Definition of the Grids and the Determination of Accelerations ...... 30 2.2.2 Illustration of the Combination of the Grid Potentials ........... 32 2.2.3 General Framework for the Choice of Parameters for the Simulations . 34 2.2.4 SUPERBOX++ versus Fortran SUPERBOX ................... 40 3 ACatalogofECsandUCDsinVariousEnvironments 43 3.1 Introduction ...................................... 43 3.2 The Observational Basis of the EO Catalog ..................... 44 3.2.1 EOs in Late-Type Galaxies .........................
    [Show full text]