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The Global Jet Structure of the Archetypical Quasar 3C 273
galaxies Article The Global Jet Structure of the Archetypical Quasar 3C 273 Kazunori Akiyama 1,2,3,*, Keiichi Asada 4, Vincent L. Fish 2 ID , Masanori Nakamura 4, Kazuhiro Hada 3 ID , Hiroshi Nagai 3 and Colin J. Lonsdale 2 1 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA 2 Massachusetts Institute of Technology, Haystack Observatory, 99 Millstone Rd, Westford, MA 01886, USA; vfi[email protected] (V.L.F.); [email protected] (C.J.L.) 3 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; [email protected] (K.H.); [email protected] (H.N.) 4 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan; [email protected] (K.A.); [email protected] (M.N.) * Correspondence: [email protected] Received: 16 September 2017; Accepted: 8 January 2018; Published: 24 January 2018 Abstract: A key question in the formation of the relativistic jets in active galactic nuclei (AGNs) is the collimation process of their energetic plasma flow launched from the central supermassive black hole (SMBH). Recent observations of nearby low-luminosity radio galaxies exhibit a clear picture of parabolic collimation inside the Bondi accretion radius. On the other hand, little is known of the observational properties of jet collimation in more luminous quasars, where the accretion flow may be significantly different due to much higher accretion rates. In this paper, we present preliminary results of multi-frequency observations of the archetypal quasar 3C 273 with the Very Long Baseline Array (VLBA) at 1.4, 15, and 43 GHz, and Multi-Element Radio Linked Interferometer Network (MERLIN) at 1.6 GHz. -
Is the Universe Expanding?: an Historical and Philosophical Perspective for Cosmologists Starting Anew
Western Michigan University ScholarWorks at WMU Master's Theses Graduate College 6-1996 Is the Universe Expanding?: An Historical and Philosophical Perspective for Cosmologists Starting Anew David A. Vlosak Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses Part of the Cosmology, Relativity, and Gravity Commons Recommended Citation Vlosak, David A., "Is the Universe Expanding?: An Historical and Philosophical Perspective for Cosmologists Starting Anew" (1996). Master's Theses. 3474. https://scholarworks.wmich.edu/masters_theses/3474 This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. IS THEUN IVERSE EXPANDING?: AN HISTORICAL AND PHILOSOPHICAL PERSPECTIVE FOR COSMOLOGISTS STAR TING ANEW by David A Vlasak A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements forthe Degree of Master of Arts Department of Philosophy Western Michigan University Kalamazoo, Michigan June 1996 IS THE UNIVERSE EXPANDING?: AN HISTORICAL AND PHILOSOPHICAL PERSPECTIVE FOR COSMOLOGISTS STARTING ANEW David A Vlasak, M.A. Western Michigan University, 1996 This study addresses the problem of how scientists ought to go about resolving the current crisis in big bang cosmology. Although this problem can be addressed by scientists themselves at the level of their own practice, this study addresses it at the meta level by using the resources offered by philosophy of science. There are two ways to resolve the current crisis. -
Star Maps: Where Are the Black Holes?
BLACK HOLE FAQ’s 1. What is a black hole? A black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. There are three kinds of black hole that we have strong evidence for: a. Stellar-mass black holes are the remaining cores of massive stars after they die in a supernova explosion. b. Mid-mass black hole in the centers of dense star clusters Credit : ESA, NASA, and F. Mirabel c. Supermassive black hole are found in the centers of many (and maybe all) galaxies. 2. Can a black hole appear anywhere? No, you need an amount of matter more than 3 times the mass of the Sun before it can collapse to create a black hole. 3. If a star dies, does it always turn into a black hole? No, smaller stars like our Sun end their lives as dense hot stars called white dwarfs. Much more massive stars end their lives in a supernova explosion. The remaining cores of only the most massive stars will form black holes. 4. Will black holes suck up all the matter in the universe? No. A black hole has a very small region around it from which you can't escape, called the “event horizon”. If you (or other matter) cross the horizon, you will be pulled in. But as long as you stay outside of the horizon, you can avoid getting pulled in if you are orbiting fast enough. 5. What happens when a spaceship you are riding in falls into a black hole? Your spaceship, along with you, would be squeezed and stretched until it was torn completely apart as it approached the center of the black hole. -
Astrometry and Optics During the Past 2000 Years
1 Astrometry and optics during the past 2000 years Erik Høg Niels Bohr Institute, Copenhagen, Denmark 2011.05.03: Collection of reports from November 2008 ABSTRACT: The satellite missions Hipparcos and Gaia by the European Space Agency will together bring a decrease of astrometric errors by a factor 10000, four orders of magnitude, more than was achieved during the preceding 500 years. This modern development of astrometry was at first obtained by photoelectric astrometry. An experiment with this technique in 1925 led to the Hipparcos satellite mission in the years 1989-93 as described in the following reports Nos. 1 and 10. The report No. 11 is about the subsequent period of space astrometry with CCDs in a scanning satellite. This period began in 1992 with my proposal of a mission called Roemer, which led to the Gaia mission due for launch in 2013. My contributions to the history of astrometry and optics are based on 50 years of work in the field of astrometry but the reports cover spans of time within the past 2000 years, e.g., 400 years of astrometry, 650 years of optics, and the “miraculous” approval of the Hipparcos satellite mission during a few months of 1980. 2011.05.03: Collection of reports from November 2008. The following contains overview with summary and link to the reports Nos. 1-9 from 2008 and Nos. 10-13 from 2011. The reports are collected in two big file, see details on p.8. CONTENTS of Nos. 1-9 from 2008 No. Title Overview with links to all reports 2 1 Bengt Strömgren and modern astrometry: 5 Development of photoelectric astrometry including the Hipparcos mission 1A Bengt Strömgren and modern astrometry .. -
Virgo the Virgin
Virgo the Virgin Virgo is one of the constellations of the zodiac, the group tion Virgo itself. There is also the connection here with of 12 constellations that lies on the ecliptic plane defined “The Scales of Justice” and the sign Libra which lies next by the planets orbital orientation around the Sun. Virgo is to Virgo in the Zodiac. The study of astronomy had a one of the original 48 constellations charted by Ptolemy. practical “time keeping” aspect in the cultures of ancient It is the largest constellation of the Zodiac and the sec- history and as the stars of Virgo appeared before sunrise ond - largest constellation after Hydra. Virgo is bordered by late in the northern summer, many cultures linked this the constellations of Bootes, Coma Berenices, Leo, Crater, asterism with crops, harvest and fecundity. Corvus, Hydra, Libra and Serpens Caput. The constella- tion of Virgo is highly populated with galaxies and there Virgo is usually depicted with angel - like wings, with an are several galaxy clusters located within its boundaries, ear of wheat in her left hand, marked by the bright star each of which is home to hundreds or even thousands of Spica, which is Latin for “ear of grain”, and a tall blade of galaxies. The accepted abbreviation when enumerating grass, or a palm frond, in her right hand. Spica will be objects within the constellation is Vir, the genitive form is important for us in navigating Virgo in the modern night Virginis and meteor showers that appear to originate from sky. Spica was most likely the star that helped the Greek Virgo are called Virginids. -
Columbiaieinstein Observations of Extragalactic X-Ray Sources
COLUMBIAIEINSTEIN OBSERVATIONS OF EXTRAGALACTIC X-RAY SOURCES William H. -M. Ku Columbia Astrophysics Laboratory I would like to report on the preliminary results of our analysis of data from the first 3 months of the Columbia Astrophysics Laboratory's (CAL) observations of extragalactic objects with the imaging proportional counter (IPC) on board the Einstein Observatory. CAL has an extensive program of extragalactic astronomy planned with the Einstein Observatory including surveys of normal galaxies, radio galaxies, active galaxies, quasars and BL Lacs, and cluste~sof galaxies. Early results from each one of these surveys have been received and analyzed at CAL. These observations have already allowed us to look as far out to the edge of the Universe as any observer in history, and they have improved our understanding of how our own Galaxy may have evolved through time. NORMAL GALAXIES X-ray observations of normal galaxies should aid us in the under- standing of our own Galaxy. Observations of the galaxies in the Local Group, such as the Large Magellanic Cloud discussed by Dr. Long, allow us to study the population of discrete X-ray sources in detail, as well as to examine diffuse emission associated with large-scale structures. Galaxies just outside the Local Group may also be studied in this way. For example, a 13 000 sec IPC image of M101, a normal spiral Sc galaxy, reveals the presence of three or four discrete sources associated with the beautiful spiral arm structure of the galaxy (Fig. 1). Possible diffuse or unresolved emission is also noticeable in the IPC image. -
Astronomy (ASTR) 1
Astronomy (ASTR) 1 ASTR 5073. Cosmology. 3 Hours. Astronomy (ASTR) An introduction to modern physical cosmology covering the origin, evolution, and structure of the Universe, based on the Theory of Relativity. (Typically offered: Courses Spring Odd Years) ASTR 2001L. Survey of the Universe Laboratory (ACTS Equivalency = PHSC ASTR 5083. Data Analysis and Computing in Astronomy. 3 Hours. 1204 Lab). 1 Hour. Study of the statistical analysis of large data sets that are prevalent in the Daytime and nighttime observing with telescopes and indoor exercises on selected physical sciences with an emphasis on astronomical data and problems. Includes topics. Pre- or Corequisite: ASTR 2003. (Typically offered: Fall, Spring and Summer) computational lab 1 hour per week. Corequisite: Lab component. (Typically offered: Fall Even Years) ASTR 2001M. Honors Survey of the Universe Laboratory. 1 Hour. An introduction to the content and fundamental properties of the cosmos. Topics ASTR 5523. Theory of Relativity. 3 Hours. include planets and other objects of the solar system, the sun, normal stars and Conceptual and mathematical structure of the special and general theories of interstellar medium, birth and death of stars, neutron stars, and black holes. Pre- or relativity with selected applications. Critical analysis of Newtonian mechanics; Corequisite: ASTR 2003 or ASTR 2003H. (Typically offered: Fall) relativistic mechanics and electrodynamics; tensor analysis; continuous media; and This course is equivalent to ASTR 2001L. gravitational theory. (Typically offered: Fall Even Years) ASTR 2003. Survey of the Universe (ACTS Equivalency = PHSC 1204 Lecture). 3 Hours. An introduction to the content and fundamental properties of the cosmos. Topics include planets and other objects of the solar system, the Sun, normal stars and interstellar medium, birth and death of stars, neutron stars, pulsars, black holes, the Galaxy, clusters of galaxies, and cosmology. -
Part I Officers in Institutions Placed Under the Supervision of the General Board
2 OFFICERS NUMBER–MICHAELMAS TERM 2009 [SPECIAL NO.7 PART I Chancellor: H.R.H. The Prince PHILIP, Duke of Edinburgh, T Vice-Chancellor: 2003, Prof. ALISON FETTES RICHARD, N, 2010 Deputy Vice-Chancellors for 2009–2010: Dame SANDRA DAWSON, SID,ATHENE DONALD, R,GORDON JOHNSON, W,STUART LAING, CC,DAVID DUNCAN ROBINSON, M,JEREMY KEITH MORRIS SANDERS, SE, SARAH LAETITIA SQUIRE, HH, the Pro-Vice-Chancellors Pro-Vice-Chancellors: 2004, ANDREW DAVID CLIFF, CHR, 31 Dec. 2009 2004, IAN MALCOLM LESLIE, CHR, 31 Dec. 2009 2008, JOHN MARTIN RALLISON, T, 30 Sept. 2011 2004, KATHARINE BRIDGET PRETTY, HO, 31 Dec. 2009 2009, STEPHEN JOHN YOUNG, EM, 31 July 2012 High Steward: 2001, Dame BRIDGET OGILVIE, G Deputy High Steward: 2009, ANNE MARY LONSDALE, NH Commissary: 2002, The Rt Hon. Lord MACKAY OF CLASHFERN, T Proctors for 2009–2010: JEREMY LLOYD CADDICK, EM LINDSAY ANNE YATES, JN Deputy Proctors for MARGARET ANN GUITE, G 2009–2010: PAUL DUNCAN BEATTIE, CC Orator: 2008, RUPERT THOMPSON, SE Registrary: 2007, JONATHAN WILLIAM NICHOLLS, EM Librarian: 2009, ANNE JARVIS, W Acting Deputy Librarian: 2009, SUSANNE MEHRER Director of the Fitzwilliam Museum and Marlay Curator: 2008, TIMOTHY FAULKNER POTTS, CL Director of Development and Alumni Relations: 2002, PETER LAWSON AGAR, SE Esquire Bedells: 2003, NICOLA HARDY, JE 2009, ROGER DERRICK GREEVES, CL University Advocate: 2004, PHILIPPA JANE ROGERSON, CAI, 2010 Deputy University Advocates: 2007, ROSAMUND ELLEN THORNTON, EM, 2010 2006, CHRISTOPHER FORBES FORSYTH, R, 2010 OFFICERS IN INSTITUTIONS PLACED UNDER THE SUPERVISION OF THE GENERAL BOARD PROFESSORS Accounting 2003 GEOFFREY MEEKS, DAR Active Tectonics 2002 JAMES ANTHONY JACKSON, Q Aeronautical Engineering, Francis Mond 1996 WILLIAM NICHOLAS DAWES, CHU Aerothermal Technology 2000 HOWARD PETER HODSON, G Algebra 2003 JAN SAXL, CAI Algebraic Geometry (2000) 2000 NICHOLAS IAN SHEPHERD-BARRON, T Algebraic Geometry (2001) 2001 PELHAM MARK HEDLEY WILSON, T American History, Paul Mellon 1992 ANTHONY JOHN BADGER, CL American History and Institutions, Pitt 2009 NANCY A. -
'-. 5 36 B6 19650268
-- '-. 5 36_B6 _ rr_nm O/ITEE I_ATUREOF THE QUASI-S_ OBJECTS F. HOYLE , University of Cambridge- C_m_ridge,Eng!and and G. R. BURBIDGE :University of California at San Diego La Jolla, California ) 19650268 1965026885-002 ON _ NA_NJEE OF THE QUASI-STELLAR OBJECTS F. HOYLE Uni,_ersity of Cambridge Cambridge, England and G. R. BURBIDGE University of California at San Diego - La Jolla, California Received July 1965 1985028885-003 ABST_ACT In this paper we discuss the origin of the quasi-stellar objects from , two different points of view: (i) that they are objects al;cosmological distances as has been commonly supposed, and (ii) that they are local obje:ts situated at distance _ 1 - l0 Mpc. In the introductory section the optical properties of the quasi-stellar objects ar_:compared with the optical properties of galaxies associated with strong radio courses and Syefert nuclei from both points of view. Section II is devoted to a d.Lscussion of (i) and on this basis it is argue_ that they are most probably the nuclei of galaxies which have reached a high density phase at which time the formation of me_sive objects and their subsequent evolution has occurred. Apart from the suggestion of Terrell little atr.entionhas been paid until now to the possibility that they are local objects and so we have considered this in considerable detail. A plausible case can now be made for supposing that they are coherent objects which have been ejected at relativistic speeds L from the nuclei of galaxies at times when they erupt to give rise to strong radio source_ and other phenomena. -
A Study of Giant Radio Galaxies at Ratan-600 173
Bull. Spec. Astrophys. Obs., 2011, 66, 171–182 c Special Astrophysical Observatory of the Russian AS, 2018 A Study of Giant Radio Galaxies at RATAN-600 M.L. Khabibullinaa, O.V. Verkhodanova, M. Singhb, A. Piryab, S. Nandib, N.V. Verkhodanovaa a Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz 369167, Russia; b Aryabhatta Research Institute of Observational Sciences, Manora Park, Nainital 263 129, India Received July 28, 2010; accepted September 15, 2010. We report the results of flux density measurements in the extended components of thirteen giant radio galaxies, made with the RATAN-600 in the centimeter range. Supplementing them with the WENSS, NVSS and GB6 survey data we constructed the spectra of the studied galaxy components. We computed the spectral indices in the studied frequency range and demonstrate the need for a detailed account of the integral contribution of such objects into the background radiation. Key words: Radio lines: galaxies—techniques: radar astronomy 1. INTRODUCTION than the one, expected from the evolutional models. As noted in [8], such radio galaxies may affect the According to the generally accepted definition, gi- processes of galaxy formation, since the pressure of ant radio galaxies (GRGs) are the radio sources with gas, outflowing from the radio source, may compress linear sizes greater than 1 Mpc, i.e. the largest ra- the cold gas clouds thus initiating the development dio sources in the Universe. They mostly belong to of stars on the one hand, and stop the formation of the morphological type FR II [1] and are identified galaxies on the other hand. -
Essential Radio Astronomy
February 2, 2016 Time: 09:25am chapter1.tex © Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. 1 Introduction 1.1 AN INTRODUCTION TO RADIO ASTRONOMY 1.1.1 What Is Radio Astronomy? Radio astronomy is the study of natural radio emission from celestial sources. The range of radio frequencies or wavelengths is loosely defined by atmospheric opacity and by quantum noise in coherent amplifiers. Together they place the boundary be- tween radio and far-infrared astronomy at frequency ν ∼ 1 THz (1 THz ≡ 1012 Hz) or wavelength λ = c/ν ∼ 0.3 mm, where c ≈ 3 × 1010 cm s−1 is the vacuum speed of light. The Earth’s ionosphere sets a low-frequency limit to ground-based radio astronomy by reflecting extraterrestrial radio waves with frequencies below ν ∼ 10 MHz (λ ∼ 30 m), and the ionized interstellar medium of our own Galaxy absorbs extragalactic radio signals below ν ∼ 2 MHz. The radio band is very broad logarithmically: it spans the five decades between 10 MHz and 1 THz at the low-frequency end of the electromagnetic spectrum. Nearly everything emits radio waves at some level, via a wide variety of emission mechanisms. Few astronomical radio sources are obscured because radio waves can penetrate interstellar dust clouds and Compton-thick layers of neutral gas. Because only optical and radio observations can be made from the ground, pioneering radio astronomers had the first opportunity to explore a “parallel universe” containing unexpected new objects such as radio galaxies, quasars, and pulsars, plus very cold sources such as interstellar molecular clouds and the cosmic microwave background radiation from the big bang itself. -
Broadband Spectral Modelling of Bent Jets of Active Galactic Nuclei Arxiv
Broadband spectral modelling of bent jets of Active Galactic Nuclei A Thesis submitted to the University of Mumbai for the Ph. D. (SCIENCE) Degree in PHYSICS Submitted By B. Sunder Sahayanathan Under the Guidance of Dr. A. K. Mitra Astrophysical Sciences Division arXiv:1109.0618v2 [astro-ph.HE] 7 Sep 2011 Bhabha Atomic Research Centre Trombay, Mumbai - 400085 October 2010 In memory of my beloved grandma Josephine... Abstract The understanding of the physics of relativistic jets from active galactic nuclei (AGN) is still incomplete. A way to understand the different features of the AGN jets is to study it broadband spectra. In general, within the limits of present observations, AGN jets are observed in radio-to-X-ray energy band and they exhibit various intrinsic features such as knots. Particularly, the blazar jets which are pointed towards the observer, are observed in radio-to-γ-ray and their radio maps exhibit internal jet structures. Moreover, the high energy emission from blazars show rapid variability. In this thesis, models have been developed to study the radiation emission processes from the knots of AGN jets as well as for blazar jets. A continuous injection plasma model is devel- oped to study the X-ray emission from the knots of sources 1136-135, 1150+497, 1354+195 and 3C 371. The knot dynamics is then studied within the framework of internal shock model. In such a scenario, knots are formed due to the collision of two successive matter blobs emitted sporadically from the central engine of AGN. Shocks, generated in such col- lisions, accelerate electrons to relativistic energies.