DOCSLIB.ORG

1964Aj 69. . 4 90E the Astronomical Journal

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
1964Aj 69. . 4 90E the Astronomical Journal 90E 4 . 69. THE ASTRONOMICAL JOURNAL VOLUME 69, NUMBER 7 SEPTEMBER 1964 Atomic Hydrogen in Galaxies* 1964AJ Eugene E. Epstein Harvard College Observatory, Cambridge 38, Massachusetts, and Radio Astronomy Program, Aerospace Corporation, Los Angeles 45, California (Received 14 April 1964) This paper deals with all currently available 21-cm H i emission line observations of galaxies: 40 galaxies investigated with the Harvard maser-equipped 60-ft antenna and 8 galaxies previously investigated else- where. H i emission was positively detected from 3 Sb, 13 Sc, and 13 Ir galaxies; for the galaxies from which H i emission has not been detected, upper limits have been established. The bluer or “later” galaxies defi- nitely tend to have higher values of 911# i/Lm, 911# i/91Z, and <r# i and smaller values of 911 than the less blue galaxies ; o-# i is the mean H i areal density when one projects the entire H i mass onto the fundamental plane of the galaxy. The average values of the pertinent parameters for the detected Sb, Sc, and Ir galaxies are : Morphological type Sb Sc Ir Number detected 3 13 13 H i mass 9E#i (solar masses) 3X109 4X109 1X109 Total mass 911 (solar masses) 3X1011 6X1010 1X1010 911# i/91Z 0.01 0.08 0.16 9E/Zpg 7 7 9 311* i/Zpg 0 .09 0 .41 1 .19 Mean H i areal density cr# i(10 3 g/cm2) 0.6 1.7 3.3 The values of 911# i/Zpg and <r# i are independent of the distance estimates. The paper also presents average values and upper limits for undetected galaxies. I. INTRODUCTION these results and the tests performed thereon for possible dependence on morphological type and other THE Harvard maser-equipped 60-ft antenna was parameters. Appendix A contains details about the used to study atomic hydrogen in galaxies. The instrument, the observation techniques, and the reduc- principal objectives of the study were : tion procedures. Appendix B presents a series of (1) To obtain the velocity distribution of the neutral, reliability tests, and Appendix C discusses the effects atomic hydrogen (H i) in each galaxy observed. We of continuum radiation on the H i radiation. can use this distribution to determine the H i content and systemic velocity of each galaxy. II. OBSERVATIONAL DATA (2) To test the H i radiation data for possible A. Observing Program correlation with morphological type and other charac- teristics of the galaxies. The observations were made with a five-channel (3) To study, as functions of assumed internal maser radiometer and the Harvard 60-ft antenna; the motions, orientation, and angular size, the variations total system-noise temperature was 100 °K, and the of the predicted H i emission from a series of galaxy observing bandwidth was 32 km/sec. Further details models; to use these models to (a) generate Hi line appear in Appendix A. profiles similar to the observed profiles and (b) estimate An ideal test of the dependence oî H i data on the errors that result from the fact that the observed morphological type would require the observation of galaxies do not appear as point sources to the Harvard equal numbers of galaxies of each type. However, this antenna. We have reported these investigations in a is not practical; in the Holmberg (1958) catalogue of separate paper (Epstein 1964). northern galaxies, one must include objects at distances of «11 Mpc to obtain as few as four Sa galaxies, Section II presents the observational program and whereas there are several times that number of Sc reduced results. Section HI discusses the determination galaxies within the same distance. Since H i emission of the H i masses and the total mass estimates ; the will in general be more difficult to detect from distant section concludes with a tabular presentation of the than from nearby galaxies, this difference in relative results of all currently available 21-cm studies of abundance precluded attempts to observe equal galaxies. Section IV presents statistical summaries of numbers of all morphological types. The observing program included the 32 galaxies * The Agassiz Station Radio Astronomy Project of Harvard College Observatory is supported by the U. S. National Science listed in Table I: 4 E’s, 2 SO^ 2 Sa’s, 6 Sb’s, 1 SBb, Foundation. 8 Sc’s and 9 Ir’s. These represent three categories of 490 © American Astronomical Society • Provided by the NASA Astrophysics Data System 90E 4 . 69. ATOMIC HYDROGEN IN GALAXIES 491 Table I. Galaxies used in the observing program. from 4438), NGC 205 (too near 224), NGC 3623l(too near 3627 and 3628), and NGC 4374 (too near 4486). 1964AJ NGC *IC Type NGC Type B. Observational Results 45 Sc 3368 Sa 55a Sc 4214* Ir Figure 1 displays the H i emission line profiles of 26 *10* Ir 4258b Sb of the galaxies listed in Table I. Figure 2 shows the 147 E 4382 SO observed rotation curves constructed for NGC 55, 300, 185 E 4449* Ir and 3109. These galaxies are of large angular size and 247* Sc 4486b E 253b Sc 4565 Sb have major axes approximately parallel to lines of 300* Sc 4594 Sa constant declination. The curve constructed for NGC *1613* Ir 4631*’b Sc 4214 has a total radial velocity extent of ^90 km/sec 1023 SO 4656* Ir and suggests an east-west extent of ~ 15' ; this curve Fornax system E 4725 Sb is not illustrated. We were unable to construct rotation 1097 SBb 4736 Sb Holmberg IIa Ir 4826 Sb curves for the remaining galaxies because it was 3109* Ir 5055 Sb impossible to assign positions with sufficient accuracy. Sextans A* Ir 5236*-b Sc (See Appendix A5 for data reduction procedures.) *2574* Ir 6946*-° Sc The position information for the rotation curve of NGC 55 indicates that the signals which contribute to a 17 i emission detected. b Continuum emission detected. the noncentral profile peak originate in the same region 0 Continuum emission provisionally detected ; because of the low Galactic («10' east of the center) as the asymmetry in the latitude, some confusion with the Galactic background exists. However, Heeschen (1961), using a higher resolution antenna, identifies this galaxy as a continuum source. Table II. Positions of rotation curve maxima. galaxies for which Humason, Mayall, and Sandage Rp Rb.o (1956) have given radial velocities: (1) The apparently NGC Type (min of arc) (min of arc) Rp/Rb.o largest previously unobserved objects in each major class in Holmberg’s catalogue, (2) several well-known 157 Sc 1* 3 0.3 224 Sb 40b 98 0.4 dwarf galaxies, and (3) five southern galaxies of large 598 Sc 16c 42 0.4 angular size not in Holmberg^ catalogue. 2903 Sc 1.6d 7 0.2 Fourteen of the fifteen Hi emission sources listed 5005 Sb Ie 4 0.2 f in Table I were first detected with the Harvard maser 5055 Sb 1.7 8 0.2 installation. Cooper et al. (1960) detected five of the fourteen during a preliminary maser investigation ; the b» Burbidge, Burbidge, and Prendergast (1961b), 0 Brandt (1960a). rest are reported here for the first time. d Mayall and Aller (1942). Burbidge, Burbidge, and Prendergast (1960b). Initial searches (only one observation at each velocity «Burbidge,f Burbidge, and Prendergast (1961a). setting within the search range) for the Sb galaxies Burbidge, Burbidge, and Prendergast (1960a). NGC 4565, 4725, 4826, and 5055 were unsuccessful. We therefore decided to make more extended obser- luminosity distribution (see de Vaucouleurs 1961b). vations of NGC 4258 and NGC 4736, the two ap- About 10% of both the total photographic luminosity parently largest and nearest Sb galaxies listed in and the total H i flux of NGC 55 originates in this Table I. Since HI emission was not positively detected region. from these two most likely-to-be-detected Sb sources, no further observations were made of the more remote III. DATA ANALYSIS and/or apparently smaller Sb galaxies. Only a limited A. The HI Masses search was made for NGC 45 because emission had already been detected from a large sample of Sc None of the signals observed during this program galaxies. was measurably broadened (see Appendix A2) ; conse- We removed an Sa galaxy, NGC 3368, from the quently, the apparent solid angles of the emitting observing program because of confusion with a con- regions (within the galaxies) which give rise to the tinum source (flux«4XlO~26 W m~2 cps-1) approxi- individual signals were treated as being small with mately one beamwidth west; this source coincides in respect to the equivalent solid angle of the antenna position with NGC 3351, a blue-nucleus Sb galaxy beam (3.2X103 sq min). The expression used by Roberts (de Vaucouleurs 1961a and Tifft 1963). (1962a) for the È i mass, Sfïl#i (in solar masses), of a Certain galaxies, though within the scope of the first source which is small with respect to the beam is category above, were not considered; these included: NGC 4438 (its small radial velocity allows possible = 2.36X RPC's2 / SydV, (1) confusion between H i emission from the Galaxy and 9Fo J-* © American Astronomical Society • Provided by the NASA Astrophysics Data System 90E 4 . 69. 492 EUGENE E. EPSTEIN KM/SEC 1964AJ I Í (o) KM/SEC 8.0 _ 4.0 Ä 2.0 co 0.0 (b) KM/SEC (O Fig. 1. The H i emission line profiles, arranged in order of increasing right ascension of the galaxies. Ordinate units of both antenna temperature and flux are used; the latter is more reliably calibrated.
Load more

Recommended publications
  • Multiband Counterparts of Two Eclipsing Ultraluminous X-Ray Sources in M 51
    MNRAS 000,1{16 (2017) Preprint 5 November 2018 Compiled using MNRAS LATEX style file v3.0 Multiband counterparts of two eclipsing ultraluminous X-ray sources in M 51 R. Urquhart,1? R. Soria,2;1;3 H.M. Johnston,3 M.W. Pakull,4 C. Motch,4 A. Schwope,5 J.C.A. Miller-Jones1 and G.E. Anderson1 1International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845, Australia 2National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China 3Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, Sydney, NSW 2006, Australia 4Observatoire astronomique, Universit´ede Strasbourg, CNRS, UMR 7550, 11 rue de l'Universit´e,67000, Strasbourg, France 5Leibniz-Institut f¨urAstrophysik Potsdam, An der Sternwarte 16, 14482, Potsdam, Germany Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We present the discovery and interpretation of ionized nebulae around two ultra- luminous X-ray sources in M 51; both sources share the rare property of show- ing X-ray eclipses by their companion stars, and are therefore prime targets for follow-up studies. Using archival Hubble Space Telescope images, we found an elon- gated, 100-pc-long emission-line structure associated with one X-ray source (CXOM51 J132940.0+471237; ULX-1 for simplicity), and a more circular, ionized nebula at the location of the second source (CXOM51 J132939.5+471244; ULX-2 for simplicity). We observed both nebulae with the Large Binocular Telescope's Multi-Object Double Spectrograph. From our analysis of the optical spectra, we argue that the gas in the ULX-1 bubble is shock-ionized, consistent with the effect of a jet with a kinetic power of ≈2 ×1039 erg s−1.
    [Show full text]
  • The Puzzle of the Strange Galaxy Made of 99.9% Dark Matter Is Solved 13 October 2020
    The puzzle of the strange galaxy made of 99.9% dark matter is solved 13 October 2020 The galaxy Dragonfly 44 was discovered in a deep survey of the Coma cluster, a cluster with several thousand galaxies. From the start, the galaxy was considered remarkable by the researchers because the quantity of dark matter they inferred was almost as much as that in the Milky Way, the equivalent of a billion solar masses. However, instead of containing around a hundred thousand million stars, as has the Milky Way, DF44 has only a hundred million stars, a thousand times Image and amplification (in color) of the ultra-diffuse fewer. This means that the amount of dark matter galaxy Dragonfly 44 taken with the Hubble space was ten thousand times greater than that of its telescope. Credit: Teymoor Saifollahi and NASA/HST. stars. If this had been true, it would have been a unique object, with almost 100 times as much dark matter as that expected from the number of its stars. At present, the formation of galaxies is difficult to understand without the presence of a ubiquitous, Nevertheless, by an exhaustive analysis of the but mysterious component, termed dark matter. system of globular cluster around Dragonfly 44, the Astronomers have measure how much dark matter researchers have detected that the total number of there is around galaxies, and have found that it globular clusters is only 20, and that the total varies between 10 and 300 times the quantity of quantity of dark matter is around 300 times that of visible matter.
    [Show full text]
  • A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra
    San Jose State University From the SelectedWorks of Aaron J. Romanowsky 2016 A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra-Diffuse Galaxy Dragonfly 44 Pieter van Dokkum, Yale University Roberto Abraham, University of Toronto Jean P. Brodie, University of California Observatories Charlie Conroy, Harvard-Smithsonian Center for Astrophysics Shany Danieli, Yale University, et al. Available at: https://works.bepress.com/aaron_romanowsky/117/ The Astrophysical Journal Letters, 828:L6 (6pp), 2016 September 1 doi:10.3847/2041-8205/828/1/L6 © 2016. The American Astronomical Society. All rights reserved. A HIGH STELLAR VELOCITY DISPERSION AND ∼100 GLOBULAR CLUSTERS FOR THE ULTRA-DIFFUSE GALAXY DRAGONFLY 44 Pieter van Dokkum1, Roberto Abraham2, Jean Brodie3, Charlie Conroy4, Shany Danieli1, Allison Merritt1, Lamiya Mowla1, Aaron Romanowsky3,5, and Jielai Zhang2 1 Astronomy Department, Yale University, New Haven, CT 06511, USA 2 Department of Astronomy & Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada 3 University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA 5 Department of Physics and Astronomy, San José State University, San Jose, CA 95192, USA Received 2016 June 20; revised 2016 July 14; accepted 2016 July 15; published 2016 August 25 ABSTRACT Recently a population of large, very low surface brightness, spheroidal galaxies was identified in the Coma cluster. The apparent survival of these ultra-diffuse galaxies (UDGs) in a rich cluster suggests that they have very high masses. Here, we present the stellar kinematics of Dragonfly44, one of the largest Coma UDGs, using a 33.5 hr fi +8 -1 integration with DEIMOS on the Keck II telescope.
    [Show full text]
  • Precollimator for X-Ray Telescope (Stray-Light Baffle) Mindrum Precision, Inc Kurt Ponsor Mirror Tech/SBIR Workshop Wednesday, Nov 2017
    Mindrum.com Precollimator for X-Ray Telescope (stray-light baffle) Mindrum Precision, Inc Kurt Ponsor Mirror Tech/SBIR Workshop Wednesday, Nov 2017 1 Overview Mindrum.com Precollimator •Past •Present •Future 2 Past Mindrum.com • Space X-Ray Telescopes (XRT) • Basic Structure • Effectiveness • Past Construction 3 Space X-Ray Telescopes Mindrum.com • XMM-Newton 1999 • Chandra 1999 • HETE-2 2000-07 • INTEGRAL 2002 4 ESA/NASA Space X-Ray Telescopes Mindrum.com • Swift 2004 • Suzaku 2005-2015 • AGILE 2007 • NuSTAR 2012 5 NASA/JPL/ASI/JAXA Space X-Ray Telescopes Mindrum.com • Astrosat 2015 • Hitomi (ASTRO-H) 2016-2016 • NICER (ISS) 2017 • HXMT/Insight 慧眼 2017 6 NASA/JPL/CNSA Space X-Ray Telescopes Mindrum.com NASA/JPL-Caltech Harrison, F.A. et al. (2013; ApJ, 770, 103) 7 doi:10.1088/0004-637X/770/2/103 Basic Structure XRT Mindrum.com Grazing Incidence 8 NASA/JPL-Caltech Basic Structure: NuSTAR Mirrors Mindrum.com 9 NASA/JPL-Caltech Basic Structure XRT Mindrum.com • XMM Newton XRT 10 ESA Basic Structure XRT Mindrum.com • XMM-Newton mirrors D. de Chambure, XMM Project (ESTEC)/ESA 11 Basic Structure XRT Mindrum.com • Thermal Precollimator on ROSAT 12 http://www.xray.mpe.mpg.de/ Basic Structure XRT Mindrum.com • AGILE Precollimator 13 http://agile.asdc.asi.it Basic Structure Mindrum.com • Spektr-RG 2018 14 MPE Basic Structure: Stray X-Rays Mindrum.com 15 NASA/JPL-Caltech Basic Structure: Grazing Mindrum.com 16 NASA X-Ray Effectiveness: Straylight Mindrum.com • Correct Reflection • Secondary Only • Backside Reflection • Primary Only 17 X-Ray Effectiveness Mindrum.com • The Crab Nebula by: ROSAT (1990) Chandra 18 S.
    [Show full text]
  • Radio Continuum and CO Emission in Star-Forming Galaxies
    A&A 385, 412–424 (2002) Astronomy DOI: 10.1051/0004-6361:20020140 & c ESO 2002 Astrophysics Radio continuum and CO emission in star-forming galaxies M. Murgia1,A.Crapsi1,2, L. Moscadelli3, and L. Gregorini1,4 1 Istituto di Radioastronomia del CNR, Via Gobetti 101, 40129, Bologna, Italy 2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy 3 Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy 4 Dipartimento di Fisica, Universit`a di Bologna, Via B. Pichat 6/2, 40127 Bologna, Italy Received 30 October 2001 / Accepted 23 January 2002 Abstract. We combine the radio continuum images from the NRAO VLA Sky Survey with the CO-line observations from the extragalactic CO survey of the Five College Radio Astronomy Observatory to study the relationship between molecular gas and the star formation rate within the disks of 180 spiral galaxies at 4500 resolution. We find a tight correlation between these quantities. On average, the ratio between the radio continuum and the CO emission is constant, within a factor of 3, both inside the same galaxy and from galaxy to galaxy. The mean star formation efficiency deduced from the radio continuum corresponds to convert 3.5% of the available molecular gas into stars on a time scale of 108 yr and depends weakly on general galaxy properties, such as Hubble type or nuclear activity. A comparison is made with another similar analysis performed using the Hα luminosity as star formation indicator. The overall agreement we find between the two studies reinforces the use of the radio luminosity as star formation rate indicator not only on global but also on local scales.
    [Show full text]
  • The Young Stellar Population of IC 1613 III
    A&A 551, A74 (2013) Astronomy DOI: 10.1051/0004-6361/201219977 & c ESO 2013 Astrophysics The young stellar population of IC 1613 III. New O-type stars unveiled by GTC-OSIRIS,, M. Garcia1,2 and A. Herrero1,2 1 Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain e-mail: [email protected] 2 Departamento de Astrofísica, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez, s/n, 38071 La Laguna, Tenerife, Spain Received 9 July 2012 / Accepted 16 November 2012 ABSTRACT Context. Very low-metallicity massive stars are key to understanding the reionization epoch. Radiation-driven winds, chief agents in the evolution of massive stars, are consequently an important ingredient in our models of the early-Universe. Recent findings hint that the winds of massive stars with poorer metallicity than the SMC may be stronger than predicted by theory. Besides calling the paradigm of radiation-driven winds into question, this result would affect the calculated ionizing radiation and mechanical feedback of massive stars, as well as the role these objects play at different stages of the Universe. Aims. The field needs a systematic study of the winds of a large sample of very metal-poor massive stars. The sampling of spectral types is particularly poor in the very early types. This paper’s goal is to increase the list of known O-type stars in the dwarf irregular galaxy IC 1613, whose metallicity is lower than the SMC’s roughly by a factor 2. Methods. Using the reddening-free Q pseudo-colour, evolutionary masses, and GALEX photometry, we built a list of very likely O-type stars.
    [Show full text]
  • HALOS, STARBURSTS, and SUPERBUBBLES in SPIRALS Joel
    HALOS, STARBURSTS, AND SUPERBUBBLES IN SPIRALS Joel N. Bregman Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090 [email protected] ABSTRACT Detectable quantities of interstellar material are present in the halo of the Milky Way galaxy and in a few edge-on spiral galaxies, largely in the form of neutral atomic gas, warm ionized material, and cosmic rays. Theoretical and observational arguments suggest that million degree gas should be present also, so sensitive ROSAT observations have been made of the large nearby edge- on spiral galaxies for the purpose of detecting hot extraplanar gas. Of the six brightest non-starburst edge-on galaxies, three exhibit extraplanar X-ray emission: NGC 891, NGC 4631, and NGC 4565. In NGC 891, the extended emission has a density scale height of 7 kpc and an extent along the disk of 13 kpc in diameter. This component is close to hydrostatic equilibrium, has a luminosity of 4.4 • 1039 erg s -1, and a mass of 10s Mo. Extended and structured extraplanar hot gas is seen around the interacting edge-on spiral NGC 4631, with X-ray emission associated with a giant loop of Ha and HI emission; spurs of X- ray emission extending from the disk are seen also. Hot gas is expected to enter the halo through superbubble breakout, and a search for superbubbles in normal spiral galaxies have shown that these phenomena are present, but of low surface brightness and are detected in only a few instances. Unlike the normal spiral galaxies where the gas is bound to the systems, the hot gas in starburst galaxies is being expelled.
    [Show full text]
  • Spatially Resolved Stellar Kinematics of the Ultra-Diffuse Galaxy Dragonfly 44
    The Astrophysical Journal, 880:91 (26pp), 2019 August 1 https://doi.org/10.3847/1538-4357/ab2914 © 2019. The American Astronomical Society. All rights reserved. Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits Pieter van Dokkum1 , Asher Wasserman2 , Shany Danieli1 , Roberto Abraham3 , Jean Brodie2 , Charlie Conroy4 , Duncan A. Forbes5, Christopher Martin6, Matt Matuszewski6, Aaron J. Romanowsky2,7 , and Alexa Villaume2 1 Astronomy Department, Yale University, 52 Hillhouse Avenue, New Haven, CT 06511, USA 2 University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA 3 Department of Astronomy & Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA 5 Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia 6 Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 278-17, Pasadena, CA 91125, USA 7 Department of Physics and Astronomy, San José State University, San Jose, CA 95192, USA Received 2019 March 31; revised 2019 May 25; accepted 2019 June 5; published 2019 July 30 Abstract We present spatially resolved stellar kinematics of the well-studied ultra-diffuse galaxy (UDG) Dragonfly44, as determined from 25.3 hr of observations with the Keck Cosmic Web Imager. The luminosity-weighted dispersion +3 −1 within the half-light radius is s12= 33-3 km s , lower than what we had inferred before from a DEIMOS spectrum in the Hα region. There is no evidence for rotation, with Vmax áñ<s 0.12 (90% confidence) along the major axis, in possible conflict with models where UDGs are the high-spin tail of the normal dwarf galaxy distribution.
    [Show full text]
  • The Extragalactic Distance Scale
    The Extragalactic Distance Scale Published in "Stellar astrophysics for the local group" : VIII Canary Islands Winter School of Astrophysics. Edited by A. Aparicio, A. Herrero, and F. Sanchez. Cambridge ; New York : Cambridge University Press, 1998 Calibration of the Extragalactic Distance Scale By BARRY F. MADORE1, WENDY L. FREEDMAN2 1NASA/IPAC Extragalactic Database, Infrared Processing & Analysis Center, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA 91125, USA 2Observatories, Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena CA 91101, USA The calibration and use of Cepheids as primary distance indicators is reviewed in the context of the extragalactic distance scale. Comparison is made with the independently calibrated Population II distance scale and found to be consistent at the 10% level. The combined use of ground-based facilities and the Hubble Space Telescope now allow for the application of the Cepheid Period-Luminosity relation out to distances in excess of 20 Mpc. Calibration of secondary distance indicators and the direct determination of distances to galaxies in the field as well as in the Virgo and Fornax clusters allows for multiple paths to the determination of the absolute rate of the expansion of the Universe parameterized by the Hubble constant. At this point in the reduction and analysis of Key Project galaxies H0 = 72km/ sec/Mpc ± 2 (random) ± 12 [systematic]. Table of Contents INTRODUCTION TO THE LECTURES CEPHEIDS BRIEF SUMMARY OF THE OBSERVED PROPERTIES OF CEPHEID
    [Show full text]
  • The Dynamical State of the Coma Cluster with XMM-Newton?
    A&A 400, 811–821 (2003) Astronomy DOI: 10.1051/0004-6361:20021911 & c ESO 2003 Astrophysics The dynamical state of the Coma cluster with XMM-Newton? D. M. Neumann1,D.H.Lumb2,G.W.Pratt1, and U. G. Briel3 1 CEA/DSM/DAPNIA Saclay, Service d’Astrophysique, L’Orme des Merisiers, Bˆat. 709, 91191 Gif-sur-Yvette, France 2 Science Payloads Technology Division, Research and Science Support Dept., ESTEC, Postbus 299 Keplerlaan 1, 2200AG Noordwijk, The Netherlands 3 Max-Planck Institut f¨ur extraterrestrische Physik, Giessenbachstr., 85740 Garching, Germany Received 19 June 2002 / Accepted 13 December 2002 Abstract. We present in this paper a substructure and spectroimaging study of the Coma cluster of galaxies based on XMM- Newton data. XMM-Newton performed a mosaic of observations of Coma to ensure a large coverage of the cluster. We add the different pointings together and fit elliptical beta-models to the data. We subtract the cluster models from the data and look for residuals, which can be interpreted as substructure. We find several significant structures: the well-known subgroup connected to NGC 4839 in the South-West of the cluster, and another substructure located between NGC 4839 and the centre of the Coma cluster. Constructing a hardness ratio image, which can be used as a temperature map, we see that in front of this new structure the temperature is significantly increased (higher or equal 10 keV). We interpret this temperature enhancement as the result of heating as this structure falls onto the Coma cluster. We furthermore reconfirm the filament-like structure South-East of the cluster centre.
    [Show full text]
  • Preliminary Evidence for a Virial Shock Around the Coma Galaxy Cluster
    Draft version May 21, 2018 A Preprint typeset using LTEX style emulateapj v. 05/12/14 PRELIMINARY EVIDENCE FOR A VIRIAL SHOCK AROUND THE COMA GALAXY CLUSTER Uri Keshet1, Doron Kushnir2, Abraham Loeb3, and Eli Waxman4 Draft version May 21, 2018 ABSTRACT Galaxy clusters, the largest gravitationally bound objects in the Universe, are thought to grow by accreting mass from their surroundings through large-scale virial shocks. Due to electron acceleration in such a shock, it should appear as a γ-ray, hard X-ray, and radio ring, elongated towards the large-scale filaments feeding the cluster, coincident with a cutoff in the thermal Sunyaev-Zel’dovich (SZ) signal. However, no such signature was found until now, and the very existence of cluster virial shocks has remained a theory. We find preliminary evidence for a large, ∼ 5 Mpc minor axis γ-ray ring around the Coma cluster, elongated towards the large scale filament connecting Coma and Abell 1367, detected at the nominal 2.7σ confidence level (5.1σ using control signal simulations). The γ-ray ring correlates both with a synchrotron signal and with the SZ cutoff, but not with Galactic tracers. The γ-ray and radio signatures agree with analytic and numerical predictions, if the shock deposits ∼ 1% of the thermal energy in relativistic electrons over a Hubble time, and ∼ 1% in magnetic fields. The implied inverse-Compton and synchrotron cumulative emission from similar shocks can significantly contribute to the diffuse extragalactic γ-ray and low frequency radio backgrounds. Our results, if confirmed, reveal the prolate structure of the hot gas in Coma, the feeding pattern of the cluster, and properties of the surrounding large scale voids and filaments.
    [Show full text]
  • National Astronomical Observatory of Japan
    National Astronomical Observatory of Japan Masanori Iye1 ABSTRACT National Astronomical Observatory is an inter-university institute serving as the national center for ground based astronomy offering observational facilities covering the optical, infrared, radio wavelength domain. NAOJ also has solar physics and geo-lunar science groups collaborating with JAXA for space missions and a theoretical group with computer simulation facilities. The outline of NAOJ, its various unique facilities, and some highlights of recent science achievements are reviewed. Subject headings: 1. The Outline of NAOJ The National Astronomical Observatory of Japan (NAOJ), as the national center of astro- nomical researches in Japan, deploys five observa- tories and three VERA stations in Japan, Subaru Telescope in Hawaii, and ALMA Observatory in Chile as shown in Fig.1. NAOJ, belonging to the National Institutes for Natural Sciences (NINS) as one of the five inter-university institutes, offers its various top-level research facilities for researchers in the world. Major facilities of NAOJ include 8.2m Subaru Telescope at Mauna Kea, Hawaii, 45m Radio Tele- scope and Radio Heliograph at Nobeyama, 1.8m telescope at Okayama Astrophysical Observatory, VERA interferometer for Galactic radio astrome- try, solar facilities at Mitaka and Norikura, super computing facility and others. In addition to these arXiv:0908.0369v1 [astro-ph.IM] 4 Aug 2009 ground based facilities, NAOJ scientists have been core members for some of the ISAS space missions, Hinode, VSOP, and Kaguya. The total number of NAOJ staff in 2007 amounts to 258, including 33 professors, 48 as- sociate professors, and 82 research associates. In addition, about 200 contract staffs are supporting the daily activities at each campus of NAOJ.
    [Show full text]