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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. -
Characterisation of Young Nearby Stars – the Ursa Major Group
FRIEDRICH-SCHILLER-UNIVERSITAT¨ JENA Physikalisch-Astronomische Fakult¨at Characterisation of young nearby stars – The Ursa Major group Dissertation zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) vorgelegt dem Rat der Physikalischen-Astronomischen Fakult¨at der Friedrich-Schiller-Universit¨at Jena von Dipl.-Phys. Matthias Ammler geboren am 10.01.1977 in Neuburg a. d. Donau Gutachter 1. Prof. Dr. Ralph Neuh¨auser 2. Dr. habil. Matthias H¨unsch 3. Prof. Dr. Artie P. Hatzes Tag der letzten Rigorosumspr¨ufung: 26. Juni 2006 Tag der ¨offentlichen Verteidigung: 11. Juli 2006 Meinen Eltern Contents List of Figures vii List of Tables ix Abstract xi Zusammenfassung xiii Remarks and Acknowledgements xv 1 Introduction 1 1.1 WhatistheUrsaMajorgroup? . 1 1.1.1 Co-movingstarsin the BigDipper constellation . .... 1 1.1.2 Stellarmotionandmovinggroups . 1 1.1.3 Formation and evolution of open clusters and associations ... 6 1.1.4 The nature of the UMa group – cluster or association, or some- thingelse? ............................ 8 1.2 WhyistheUMagroupinteresting?. 8 1.2.1 Asnapshotinstellarevolution . 8 1.2.2 Alaboratoryinfrontofthedoor . 9 1.2.3 Thecensusofthesolarneighbourhood . 10 1.3 ConstrainingtheUMagroup–previousapproaches . ..... 11 1.3.1 Spatialclustering . 11 1.3.2 Kinematic criteria – derived from a “canonical” memberlist . 12 1.3.3 Kinematic parameters – derived from kinematic clustering ... 15 1.3.4 Stellarparametersandabundances . 17 1.3.5 TheageoftheUMagroup–photometriccriteria . 19 1.3.6 Spectroscopicindicatorsforageandactivity . .... 19 1.3.7 Combining kinematic, spectroscopic, and photometric criteria . 21 1.4 Anewhomogeneousspectroscopicstudy . 21 1.4.1 Definingthesample ....................... 22 1.4.2 Howtoobtainprecisestellarparameters? . .. 23 2 Observations,reductionandcalibration 25 2.1 Requireddata ............................... 25 2.2 Instruments ............................... -
Binocular Universe: Sly Fox September 2010 Phil Harrington
Binocular Universe is available every month on Cloudynights.com Binocular Universe: Sly Fox September 2010 Phil Harrington ast month's Stellafane convention, held atop Breezy Hill outside of Springfield, Vermont, was the best in recent memory. The skies were the Lclearest we've had in years, giving us a chance to enjoy the beauty of the summer Milky Way, which stretched from horizon to horizon. Armed with my trusty 10x50 and 16x70 binoculars, I sat back in my reclining chair and swept the plane of our Galaxy in pursuit of some old friends and new conquests. Above: Summer star map from Star Watch by Phil Harrington Binocular Universe is available every month on Cloudynights.com Above: Finder chart for this month's Binocular Universe. Chart adapted from Touring the Universe through Binoculars Atlas (TUBA), www.philharrington.net/tuba.htm Binocular Universe is available every month on Cloudynights.com Here are a few gems I bumped into along the way as I viewed the tiny constellation of Vulpecula the Fox. Vulpecula is a faint summertime constellation wedged between Cygnus (the Swan) to the north and Sagitta (the Arrow) to the south. None of Vulpecula’s stars shine brighter than magnitude 4.5, so seeing a fox here is a tall order indeed. But the sly Fox holds many binocular treasures for those who the time to seek them out. Vulpecula was created in 1687 by the Polish astronomer Johannes Hevelius. His original drawing showed a small fox carrying a hapless goose in its mouth. He called the combination Vulpecula et Anser ("the little fox and the goose"). -
NASA's Goddard Space Flight Center Laboratory for High Energy
1 NASA’s Goddard Space Flight Center Laboratory for High Energy Astrophysics Greenbelt, Maryland 20771 @S0002-7537~99!00301-7# This report covers the period from July 1, 1997 to June 30, Toshiaki Takeshima, Jane Turner, Ken Watanabe, Laura 1998. Whitlock, and Tahir Yaqoob. This Laboratory’s scientific research is directed toward The following investigators are University of Maryland experimental and theoretical research in the areas of X-ray, Scientists: Drs. Keith Arnaud, Manuel Bautista, Wan Chen, gamma-ray, and cosmic-ray astrophysics. The range of inter- Fred Finkbeiner, Keith Gendreau, Una Hwang, Michael Loe- ests of the scientists includes the Sun and the solar system, wenstein, Greg Madejski, F. Scott Porter, Ian Richardson, stellar objects, binary systems, neutron stars, black holes, the Caleb Scharf, Michael Stark, and Azita Valinia. interstellar medium, normal and active galaxies, galaxy clus- Visiting scientists from other institutions: Drs. Vadim ters, cosmic-ray particles, and the extragalactic background Arefiev ~IKI!, Hilary Cane ~U. Tasmania!, Peter Gonthier radiation. Scientists and engineers in the Laboratory also ~Hope College!, Thomas Hams ~U. Seigen!, Donald Kniffen serve the scientific community, including project support ~Hampden-Sydney College!, Benzion Kozlovsky ~U. Tel such as acting as project scientists and providing technical Aviv!, Richard Kroeger ~NRL!, Hideyo Kunieda ~Nagoya assistance to various space missions. Also at any one time, U.!, Eugene Loh ~U. Utah!, Masaki Mori ~Miyagi U.!, Rob- there are typically between twelve and eighteen graduate stu- ert Nemiroff ~Mich. Tech. U.!, Hagai Netzer ~U. Tel Aviv!, dents involved in Ph.D. research work in this Laboratory. Yasushi Ogasaka ~JSPS!, Lev Titarchuk ~George Mason U.!, Currently these are graduate students from Catholic U., Stan- Alan Tylka ~NRL!, Robert Warwick ~U. -
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. -
Naming the Extrasolar Planets
Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named. -
Winter Observing Notes
Wynyard Planetarium & Observatory Winter Observing Notes Wynyard Planetarium & Observatory PUBLIC OBSERVING – Winter Tour of the Sky with the Naked Eye NGC 457 CASSIOPEIA eta Cas Look for Notice how the constellations 5 the ‘W’ swing around Polaris during shape the night Is Dubhe yellowish compared 2 Polaris to Merak? Dubhe 3 Merak URSA MINOR Kochab 1 Is Kochab orange Pherkad compared to Polaris? THE PLOUGH 4 Mizar Alcor Figure 1: Sketch of the northern sky in winter. North 1. On leaving the planetarium, turn around and look northwards over the roof of the building. To your right is a group of stars like the outline of a saucepan standing up on it’s handle. This is the Plough (also called the Big Dipper) and is part of the constellation Ursa Major, the Great Bear. The top two stars are called the Pointers. Check with binoculars. Not all stars are white. The colour shows that Dubhe is cooler than Merak in the same way that red-hot is cooler than white-hot. 2. Use the Pointers to guide you to the left, to the next bright star. This is Polaris, the Pole (or North) Star. Note that it is not the brightest star in the sky, a common misconception. Below and to the right are two prominent but fainter stars. These are Kochab and Pherkad, the Guardians of the Pole. Look carefully and you will notice that Kochab is slightly orange when compared to Polaris. Check with binoculars. © Rob Peeling, CaDAS, 2007 version 2.0 Wynyard Planetarium & Observatory PUBLIC OBSERVING – Winter Polaris, Kochab and Pherkad mark the constellation Ursa Minor, the Little Bear. -
The X-Ray Nuclei of Intermediate-Redshift Radio Sources
Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 18 April 2018 (MN LATEX style file v2.2) The X-ray nuclei of intermediate-redshift radio sources M.J. Hardcastle1, D.A. Evans2 and J.H. Croston1 1 School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB 2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 18 April 2018 ABSTRACT We present a Chandra and XMM-Newton spectral analysis of the nuclei of the radio galax- ies and radio-loud quasars from the 3CRR sample in the redshift range 0.1 <z< 0.5. In the range of radio luminosity sampled by these objects, mostly FRIIs, it has been clear for some time that a population of radio galaxies (‘low-excitation radio galaxies’) cannot easily participate in models that unify narrow-line radio galaxies and broad-line objects. We show that low-excitation and narrow-line radio galaxies have systematically different nuclear X- ray properties: while narrow-line radio galaxies universally show a heavily absorbed nuclear X-ray component, such a heavily absorbed component is rarely found in sources classed as low-excitation objects. Combining our data with the results of our earlier work on the z < 0.1 3CRR sources, we discuss the implications of this result for unified models, for the origins of mid-infrared emission from radio sources, and for the nature of the apparent FRI/FRII di- chotomyin the X-ray. The lack of direct evidence for accretion-related X-ray emission in FRII LERGs leads us to argue that there is a strong possibility that some, or most, FRII LERGs ac- crete in a radiatively inefficient mode. -
On the Polar Distances of the Greenwich Transit Circle
fi 1260-1263. l'he prominence, which iR due in many astronoiiiicsl re- ortlcr to restore this uniforiiiify , which is otiviously of the searches to the long and excellent series of the Greenwich iiiost esseritial iiriporhiicbe, 1 have rel'errctl all the otiser- mericliorial oliservations, gives to any changes of the instrri- vatioiis to the Circle reatlirigs. which corresporrtl to the Naclir nients, by means of which these ohservatioiis are procurecl, observations of the wire. It iiiight have heen tlcsirahle to a higher and more general importance, than they woulcl other- get rid, as much as pnssilile, of' pere~nalecpitions in the wise possess. Hence the interest, with which astrononicrs reading of iiiicroscope - iiiicronieters etc. hy iisiclg for each are wont to regRrtl the construction and cfhiency of any new observer his own Zenithpoints. A closer inspec:tiori sjiotv,, instrunient of superior pretensions, is greatly enhanced in however, that, owing to several ciiwes, this (:nurse is for the case of the powerful Greenwich Transit Circle, and the the past observations inipracticable. I have 'coiiserperitly asiral question, concerning the degree of correctness, which considered it best to adopt the same periods of uri;iltered the results of a new apparatus have attained, acquires addi- Zenithpoints, as have Iieerl used in the Greenwiclr rechictioris. tional claims to be answered. As I an1 not aware, that a The values of the corrections, which it was accordingly seces- strict determination of this point has yet been attempted, 1 sary to apply to the single ohservations, fluctuate I)ct\veeri shall here niake it the suhject of inquiry with reepect to -fO"45 and TO"71. -
THE POLARIZATION of RADIO GALAXIES -Its Structure at Low Frequencies
STELLINGEN behorende bij het proefschrift THE POLARIZATION OF RADIO GALAXIES -its structure at low frequencies- 1. De structuur van de polarisatieverdelingen in uitgebreide extragalactische radiobronnen toont aan dat de veelgemaakte aanname van cilinder symmetrie voor de radiocomponenten onvolledig is (dit proefschrift). 2. Voor multispectrale vergelijkingen van radiokaarten van uitgebreide extragalactische stelsels ware het gewenst dat de Westerbork Synthese Radio Telescoop wordt uitgebreid met ontvangers bij een frequentie ergens tussen 610 MHz en 1400 MHz. 3. Het verloop van de spectrale index in zogenaamde edge-brightened double radio sources is slechts afhankelijk van de spectrale indices van de hot spots (dit proefschrift). 4. In de radiosterrenkunde blijft de theorie te ver achter bij de vele goede waarnemingen. 5. Om een goede astronoom te zijn moet men geloven dat het te bestuderen object de sleutel tot het heelal levert. 6. Bemande ruimtevaart moet waar mogelijk vermeden worden. 7. Sporters moeten zelf kunnen beslissen of zij een politiek omstreden evenement boycotten of niet. 8. Gelijktijdige pauze op alle Nederlandse astronomische instituten verhoogt de doelmatigheid. 9. De verwijzing private communication in wetenschappelijke literatuur is onacceptabel. 10. Het niet respecteren van Oost-Europese sportprestaties miskent het fenomeen topsport. 11. De huidige opzet van de dames tafeltennis competitie is nadelig voor het algehele dames spelniveau. W.J. Jagers Leiden, 2 december 1986 THE POLARIZATION OF RADIO GALAXIES its structure at low frequencies THE POLARIZATION OF RADIO GALAXIES its structure at low frequencies PROEFSCHRIFT ter verkrijging van de graad van Doctor in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit te Leiden, op gezag van de Rector Magnificus Dr. -
A Basic Requirement for Studying the Heavens Is Determining Where In
Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short). -
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.