DOCSLIB.ORG

Galaxies AS7007, 2012 Lecture 2: the Milky Way and Local Group

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Galaxies AS7007, 2012 Lecture 2: the Milky Way and Local Group 2012-03-23 Galaxies AS7007, 2012 Outline I Lecture 2: The Milky Way and Local Group • The Milky Way Galaxy – Disk, Bulge, Stellar Halo, Dark Halo – The Galactic Centre – Galactic Rotation • The Local Galaxy Group – Local Group “Geography” & Inventory – The Large and Small Magellanic Clouds – The Magellanic Stream – Satellites of the Milky Way – The Andromeda Galaxy & M33 • Outside the Local Group The Milky Way Galaxy The Milky Way Galaxy • Disk (Thin & Thick) • Bulge • Stellar Halo • Dark Halo • Nucleus (Supermassive Black Hole) The Milky Way Galaxy The Milky Way Galaxy • Spiral galaxy of type Sbc or SABbc • The concept of populations: • Contains about 2 — 4 ×10 11 stars – Three types with increasing age: population I, II & III. Pop III stars are the first to form in the universe. z – No strict dividing line between the types φ R – Less used today, except pop III which is a hot topic Galactic in the high-redshift Universe Sun centre • Correlation between age and metallicity (amount of Galactic coordinates heavy elements) → can obtain information both = − − about when and where the stars formed n(,,) R z S n(0,0,S ) exp[ R/ hR ( s )] exp[ z/ hz ( s )] hR: Scale length, h z: Scale height S: Stellar type 1 2012-03-23 The Milky Way Stellar Disk I The Milky Way Stellar Disk II • Radius of the disk: > 15 kpc • Stars form in clusters and associations Open clusters: • Scalelength h r of the disk: 2—4 kpc • × 9 – Few hundred stars at most • Disk luminosity: 15—20 10 Lsolar × 10 – Luminosity 100--30000 Lsolar • Stellar Disk mass: 6 10 Msolar • Thin disk: – Core radius ~ few pc – Young (Only ~5% more than 1 Gyr old) – Scaleheight h z : 300—400 pc – Contains 95% of all disk stars & all the young ones – Mass segregation – High metallicity • Stars form in clusters and associations • Thick disk: • Associations: – Scaleheight: 1000—1500 pc – Not gravitationally bound Lower metallicity – – Forms temporary systems The Milky Way Bulge Does the Milky Way have a classical bulge or pseudobulge? The jury is out… • Flattened (a/b ≈ 0.6), radius ~ 1 kpc • Possibly contains bar (2—3 kpc long) • Rotates in same direction as disk stars, but slower (≈ 100 km/s) • Contributes 20% of the MW luminosity • Stars several Gyr old, but younger than in halo Classical bulge ≈ • Average stellar metallicity 0.5 Z solar Classical bulge: Resembling a small elliptical galaxy, formed through mergers Pseudobulge: Disk-like properties, formed internally (so-called ”secular evolution”). No mergers required. The Milky Way Halo I The Milky Way Halo II • Somewhat flattened, but rounder than bulge • Globular clusters • Radius ≈ 50 kpc – Up to 1 million stars – Total mass ∼ 10 5 Msolar ∝ -3.5 • Stellar density r – No dark matter (at least not • Total mass in halo stars: ~ 10 9 Solar masses anymore) 1/1000 of all local stars belong to halo – Core radius < 1 pc • – Tidal / truncation radius 20-30 pc • Eccentric orbits, sometimes retrograde – About 150 objects known, ages 10—14 Gyr (oldest objects in the Galaxy) Latest stuff (not in textbook): May have two components – Typically very metal-poor (inner and outer halo) with different properties 2 2012-03-23 Intermission: Which of these The Milky Way Dark Halo is not a globular cluster? • Radius > 100 kpc • Contributes ~ 90% of the mass inside 100 kpc • Content unknown… The Milky Way Gaseous Disk The Milky Way Gaseous Disk Neutral hydrogen • 4—8 × 10 9 solar masses HI × 9 • 2—4 10 solar masses H 2 (but uncertain) • Dust ∼ 1 % of HI mass The Milky Way Gaseous Disk The Milky Way Gaseous Disk Ionized hydrogen HI H2 HII 3 2012-03-23 The Milky Way Centre The Milky Way Centre • Infrared light shows a dense star cluster which peaks at the center, near Sagittarius A*. • The high velocities of the stars require a mass of ∼ 6 ∼∼2 x 10 Msolar within 1 pc • Stars are only 1000 AU apart • Collisions every ≈≈≈ 10 6 years! • The centre of the star cluster may host a Supermassive Black Hole (although somewhat lightweight) 1 m Radio observations Galactic Rotation Galactic Rotation • Differential rotation • Neutral hydrogen: 21 cm line • Distance Sun-centre: 8 Kpc • Sun’s Velocity around the centre 220 km/s • One revolution in 250 Myr Galactic Rotation The Local Group • The Local Galaxy Group – Local Group “Geography” & Inventory – The Large and Small Magellanic Clouds – The Magellanic Stream – Satellites of the Milky Way – The Andromeda Galaxy & M33 4 2012-03-23 Local Group “Geography” The Local Group Inventory • Radius ∼1.2 Mpc • Held together by gravity – decoupled from Hubble flow • 3 spirals: Milky Way, M31, and M33 • Two more massive galaxies: – Irregular Large Magellanic Cloud – Small (dwarf) elliptical galaxy M32 • The rest are dwarf galaxies (dI, dE, dSph) with MV > -18 The Local Group Inventory The Large Magellanic Cloud (LMC) • The Local Group does not contain: –Blue compact dwarf galaxies –Dwarf spirals –Massive ellipticals –Active galaxies The Small Magellanic Cloud (SMC) The Magellanic Clouds LLMMCC SSMMCC Diameter 24 deg. 7 deg. Distance 50 kpc 63 kpc Total mass 6 ××11009 s.s.mm.. 22×× 11009 s.s.mm.. Luminosity ~10% of MW ~1% of MW HI mass 7 ×× 11008 s.s.mm.. 66..55×× 11008 s.s.mm.. ZZ 0.70 solar 0.25 solar M(HI)/M(total) 00..0099 00..3322 5 2012-03-23 The 11 “Classical” Satellites The Magellanic Stream & Bridge of the Milky Way • Magellanic Bridge: • LMC – HI bridge between LMC and SMC • SMC ≈ Fornax – Size 20 kpc • But dark matter theory predicts Mass: 2 ×10 8 solar masses HI • Sagittarius – factor of ~ 10 more! – Contains stars formed 10—25 Myr ago • Leo I (DDO 74) – Could have formed 200 Myr ago when LMC and • Sculptor Are there dark galaxies…? SMC where the closest • Leo II (DDO 93) • Magellanic Stream: • Sextans Carina – Gas trailing behind LMC and SMC • • Ursa Minor – Wraps 1/3 around the sky • Draco (DDO 216) Ultrafaint dwarf galaxies Stellar Populations • Some of the most dark matter-dominated systems known Resolved Unresolved • About 10 discovered in the Sloan Digital Sky Survey after 2005 Individual stars can be analyzed Integrated spectroscopy / Applicable for Milky Way star clusters photometry only and the most nearby galaxies The most common case in extragalactic astronomy Finding ultrafaint dwarf galaxies using Finding ultrafaint dwarf galaxies using resolved stars resolved stars Actual picture of the sky Resolved stars in same area Just old, metal-poor stars Same, filtered and smoothed (foreground stars dominate) (galaxy size assumed) 6 2012-03-23 Andromeda, Milky Way, M33 The Andromeda Galaxy & M33 - The Big Spirals of the Local Group- • Hubble type: Sb, Sbc/Sc, Sc • Luminosity: 1.5 × MW, 1 × MW, 0.35 × MW • Andromeda & The Milky Way have warped disks, probably caused by interaction with M32 and Magellanic Clouds • Milky Way & Andromeda may collide in ~ 5 Gyrs M31 (Andromeda) M33 (NGC 598) Outside the Local Group 7.
Load more

Recommended publications
  • The Parkes H I Survey of the Magellanic System
    A&A 432, 45–67 (2005) Astronomy DOI: 10.1051/0004-6361:20040321 & c ESO 2005 Astrophysics The Parkes H I Survey of the Magellanic System C. Brüns1,J.Kerp1, L. Staveley-Smith2, U. Mebold1,M.E.Putman3,R.F.Haynes2, P. M. W. Kalberla1,E.Muller4, and M. D. Filipovic2,5 1 Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: [email protected] 2 Australia Telescope National Facility, CSIRO, PO Box 76, Epping NSW 1710, Australia 3 Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA 4 Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612, USA 5 University of Western Sydney, Locked Bag 1797, Penrith South, DC, NSW 1797, Australia Received 24 February 2004 / Accepted 27 October 2004 Abstract. We present the first fully and uniformly sampled, spatially complete H survey of the entire Magellanic System with high velocity resolution (∆v = 1.0kms−1), performed with the Parkes Telescope. Approximately 24 percent of the southern skywascoveredbythissurveyona≈5 grid with an angular resolution of HPBW = 14.1. A fully automated data-reduction scheme was developed for this survey to handle the large number of H spectra (1.5 × 106). The individual Hanning smoothed and polarization averaged spectra have an rms brightness temperature noise of σ = 0.12 K. The final data-cubes have an rms noise of σrms ≈ 0.05 K and an effective angular resolution of ≈16 . In this paper we describe the survey parameters, the data- reduction and the general distribution of the H gas. The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are associated with huge gaseous features – the = Magellanic Bridge, the Interface Region, the Magellanic Stream, and the Leading Arm – with a total H mass of M(H ) 8 2 4.87 × 10 M d/55 kpc ,ifallH gas is at the same distance of 55 kpc.
    [Show full text]
  • VMC – the VISTA Survey of the Magellanic System Metallicity Of
    Dr Maria‐Rosa Cioni VMC – the VISTA survey of the Magellanic System (Gal-Exgal survey) Metallicity of stellar populaons Moon of stellar populaons ESO spectroscopic survey workshop ESO-Garching, Germany, 9-10 March 2009 The VISTA survey of the Magellanic System ESO Public Survey 2009-2014 The most sensive near‐IR survey across the LMC, SMC, The team Bridge and part of the Stream M. Cioni, K. Bekki, G. Clemenni, W. de Blok, J. Emerson, C. Evans, R. de Grijs, B. Gibson, L. Girardi, M. Groenewegen, 4m Telescope V. Ivanov, M. Marconi, C. Mastropietro, B. Moore, R. Napiwotzki, T. Naylor, J. Oliveira, V. Ripepi, J. van Loon, M. Wilkinson, P. Wood 1.5 deg2 FOV United Kingdom, Italy, Belgium, Chile, France, Switzerland, South Africa, Australia http://star.herts.ac.uk/~mcioni/vmc/ 0. Observe the Magellanic System 2 ≈180 deg 3 filters ‐ YJKs 15 epochs (12 in KS and 3 in YJ; once simultaneous colours) S/N=10 at: Y=21.9, J=21.4, Ks=20.3 (Ks≈19 single epoch) Seeing 0.8 arcsec – average Spaal resoluon 0.34 pix/arcsec (0.51 arcsec instrument PSF) Service mode observing 1840 hours / 240 nights http://star.herts.ac.uk/~mcioni/vmc/ I. Derive the spaally resolved SFH Synthec diagram of a typical LMC stellar field as expected from VMC data. This field covers 1 VISTA detector! Accuracy: metallicity S/N=10 0.1 dex and age 20% in 0.1 deg2 Kerber et al 2009 http://star.herts.ac.uk/~mcioni/vmc/ II. Trace the 3D structure as a funcon of me The LMC is a few kpc thick and the SMC up to 20 kpc RR Lyrae stars are excellent distance indicators in the near‐IR First applicaon to the LMC bar to derive the LMC distance (Szewczyk et al 2008) – 0.2 kpc accuracy The structure of the Magellanic System will be measured using Cepheid variables, the red clump luminosity, the p of the red giant brach, etc.
    [Show full text]
  • Constructing a Galactic Coordinate System Based on Near-Infrared and Radio Catalogs
    A&A 536, A102 (2011) Astronomy DOI: 10.1051/0004-6361/201116947 & c ESO 2011 Astrophysics Constructing a Galactic coordinate system based on near-infrared and radio catalogs J.-C. Liu1,2,Z.Zhu1,2, and B. Hu3,4 1 Department of astronomy, Nanjing University, Nanjing 210093, PR China e-mail: [jcliu;zhuzi]@nju.edu.cn 2 key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China 3 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China 4 Graduate School of Chinese Academy of Sciences, Beijing 100049, PR China e-mail: [email protected] Received 24 March 2011 / Accepted 13 October 2011 ABSTRACT Context. The definition of the Galactic coordinate system was announced by the IAU Sub-Commission 33b on behalf of the IAU in 1958. An unrigorous transformation was adopted by the Hipparcos group to transform the Galactic coordinate system from the FK4-based B1950.0 system to the FK5-based J2000.0 system or to the International Celestial Reference System (ICRS). For more than 50 years, the definition of the Galactic coordinate system has remained unchanged from this IAU1958 version. On the basis of deep and all-sky catalogs, the position of the Galactic plane can be revised and updated definitions of the Galactic coordinate systems can be proposed. Aims. We re-determine the position of the Galactic plane based on modern large catalogs, such as the Two-Micron All-Sky Survey (2MASS) and the SPECFIND v2.0. This paper also aims to propose a possible definition of the optimal Galactic coordinate system by adopting the ICRS position of the Sgr A* at the Galactic center.
    [Show full text]
  • Messier Objects
    Messier Objects From the Stocker Astroscience Center at Florida International University Miami Florida The Messier Project Main contributors: • Daniel Puentes • Steven Revesz • Bobby Martinez Charles Messier • Gabriel Salazar • Riya Gandhi • Dr. James Webb – Director, Stocker Astroscience center • All images reduced and combined using MIRA image processing software. (Mirametrics) What are Messier Objects? • Messier objects are a list of astronomical sources compiled by Charles Messier, an 18th and early 19th century astronomer. He created a list of distracting objects to avoid while comet hunting. This list now contains over 110 objects, many of which are the most famous astronomical bodies known. The list contains planetary nebula, star clusters, and other galaxies. - Bobby Martinez The Telescope The telescope used to take these images is an Astronomical Consultants and Equipment (ACE) 24- inch (0.61-meter) Ritchey-Chretien reflecting telescope. It has a focal ratio of F6.2 and is supported on a structure independent of the building that houses it. It is equipped with a Finger Lakes 1kx1k CCD camera cooled to -30o C at the Cassegrain focus. It is equipped with dual filter wheels, the first containing UBVRI scientific filters and the second RGBL color filters. Messier 1 Found 6,500 light years away in the constellation of Taurus, the Crab Nebula (known as M1) is a supernova remnant. The original supernova that formed the crab nebula was observed by Chinese, Japanese and Arab astronomers in 1054 AD as an incredibly bright “Guest star” which was visible for over twenty-two months. The supernova that produced the Crab Nebula is thought to have been an evolved star roughly ten times more massive than the Sun.
    [Show full text]
  • The Puzzling Nature of Dwarf-Sized Gas Poor Disk Galaxies
    Dissertation submitted to the Department of Physics Combined Faculties of the Astronomy Division Natural Sciences and Mathematics University of Oulu Ruperto-Carola-University Oulu, Finland Heidelberg, Germany for the degree of Doctor of Natural Sciences Put forward by Joachim Janz born in: Heidelberg, Germany Public defense: January 25, 2013 in Oulu, Finland THE PUZZLING NATURE OF DWARF-SIZED GAS POOR DISK GALAXIES Preliminary examiners: Pekka Heinämäki Helmut Jerjen Opponent: Laura Ferrarese Joachim Janz: The puzzling nature of dwarf-sized gas poor disk galaxies, c 2012 advisors: Dr. Eija Laurikainen Dr. Thorsten Lisker Prof. Heikki Salo Oulu, 2012 ABSTRACT Early-type dwarf galaxies were originally described as elliptical feature-less galax- ies. However, later disk signatures were revealed in some of them. In fact, it is still disputed whether they follow photometric scaling relations similar to giant elliptical galaxies or whether they are rather formed in transformations of late- type galaxies induced by the galaxy cluster environment. The early-type dwarf galaxies are the most abundant galaxy type in clusters, and their low-mass make them susceptible to processes that let galaxies evolve. Therefore, they are well- suited as probes of galaxy evolution. In this thesis we explore possible relationships and evolutionary links of early- type dwarfs to other galaxy types. We observed a sample of 121 galaxies and obtained deep near-infrared images. For analyzing the morphology of these galaxies, we apply two-dimensional multicomponent fitting to the data. This is done for the first time for a large sample of early-type dwarfs. A large fraction of the galaxies is shown to have complex multicomponent structures.
    [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]
  • Elements of Astronomy and Cosmology Outline 1
    ELEMENTS OF ASTRONOMY AND COSMOLOGY OUTLINE 1. The Solar System The Four Inner Planets The Asteroid Belt The Giant Planets The Kuiper Belt 2. The Milky Way Galaxy Neighborhood of the Solar System Exoplanets Star Terminology 3. The Early Universe Twentieth Century Progress Recent Progress 4. Observation Telescopes Ground-Based Telescopes Space-Based Telescopes Exploration of Space 1 – The Solar System The Solar System - 4.6 billion years old - Planet formation lasted 100s millions years - Four rocky planets (Mercury Venus, Earth and Mars) - Four gas giants (Jupiter, Saturn, Uranus and Neptune) Figure 2-2: Schematics of the Solar System The Solar System - Asteroid belt (meteorites) - Kuiper belt (comets) Figure 2-3: Circular orbits of the planets in the solar system The Sun - Contains mostly hydrogen and helium plasma - Sustained nuclear fusion - Temperatures ~ 15 million K - Elements up to Fe form - Is some 5 billion years old - Will last another 5 billion years Figure 2-4: Photo of the sun showing highly textured plasma, dark sunspots, bright active regions, coronal mass ejections at the surface and the sun’s atmosphere. The Sun - Dynamo effect - Magnetic storms - 11-year cycle - Solar wind (energetic protons) Figure 2-5: Close up of dark spots on the sun surface Probe Sent to Observe the Sun - Distance Sun-Earth = 1 AU - 1 AU = 150 million km - Light from the Sun takes 8 minutes to reach Earth - The solar wind takes 4 days to reach Earth Figure 5-11: Space probe used to monitor the sun Venus - Brightest planet at night - 0.7 AU from the
    [Show full text]
  • HI in the M31/M33 Environment
    HI in the M31/M33 Environment A thesis presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Master of Science Nicole L. Free November 2010 © 2010 Nicole L. Free. All Rights Reserved. 2 This thesis titled HI in the M31/M33 Environment by NICOLE L. FREE has been approved for the Department of Physics and Astronomy and the College of Arts and Sciences by Felix J. Lockman Adjunct Professor of Physics and Astronomy Joseph C. Shields Professor of Physics and Astronomy Benjamin M. Ogles Dean, College of Arts and Sciences 3 ABSTRACT FREE, NICOLE L., M.S., November 2010, Physics and Astronomy HI in the M31/M33 Environment (70 pp.) Director of Thesis: Felix J. Lockman and Joseph C. Shields With recent debate about a reported neutral hydrogen, HI, streamer between M33 and M31, we set out to determine the existence of the HI streamer. Using the National Radio Astronomy Observatory’s 100 m Green Bank Telescope, with 9.1´ angular resolution, we mapped the HI in the region from Wright’s Cloud and M33 through the location of the streamer features, as reported by Braun and Thilker (2004). To verify the findings of Braun and Thilker, we also performed pointed observations at two of the three local maxima within their maps. From our observations, we were able to confirm the existence of the three local maxima points. The three features have column densities ranging from 2.3 to 5.4 , with most being of the order of magnitude of the latter.
    [Show full text]
  • A Gas Cloud on Its Way Towards the Super-Massive Black Hole in the Galactic Centre
    1 A gas cloud on its way towards the super-massive black hole in the Galactic Centre 1 1,2 1 3 4 4,1 5 S.Gillessen , R.Genzel , T.K.Fritz , E.Quataert , C.Alig , A.Burkert , J.Cuadra , F.Eisenhauer1, O.Pfuhl1, K.Dodds-Eden1, C.F.Gammie6 & T.Ott1 1Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching, Germany ( [email protected], [email protected] ) 2Department of Physics, Le Conte Hall, University of California, 94720 Berkeley, USA 3Department of Astronomy, University of California, 94720 Berkeley, USA 4Universitätssternwarte der Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 München, Germany 5Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile 6Center for Theoretical Astrophysics, Astronomy and Physics Departments, University of Illinois at Urbana-Champaign, 1002 West Green St., Urbana, IL 61801, USA Measurements of stellar orbits1-3 provide compelling evidence4,5 that the compact radio source Sagittarius A* at the Galactic Centre is a black hole four million times the mass of the Sun. With the exception of modest X-ray and infrared flares6,7, Sgr A* is surprisingly faint, suggesting that the accretion rate and radiation efficiency near the event horizon are currently very low3,8. Here we report the presence of a dense gas cloud approximately three times the mass of Earth that is falling into the accretion zone of Sgr A*. Our observations tightly constrain the cloud’s orbit to be highly eccentric, with an innermost radius of approach of only ~3,100 times the event horizon that will be reached in 2013.
    [Show full text]
  • ASKAP and Meerkat Surveys of the Magellanic Clouds
    ASKAP and MeerKAT surveys of the Magellanic Clouds Jacco Th. van Loon Lennard-Jones Laboratories, Keele University, ST5 5BG, United Kingdom E-mail: [email protected] The GASKAP Team Hector Arce, Amanda Bailey, Indra Bains, Ayesha Begum, Kenji Bekki, Nadya Ben Bekhti, Joss Bland-Hawthorn, Kate Brooks, Chris Brunt, Michael Burton, James Caswell, Maria Cunningham, John Dickey, Kevin Douglas, Simon Ellingsen, Jayanne English, Robert Estalella, Alyson Ford, Tyler Foster, Bryan Gaensler, Jay Gallagher, Steven Gibson, José Girart, Paul Goldsmith, José F. Gómez, Yolanda Gómez, Anne Green, James Green, Matt Haffner, Carl Heiles, Fabian Heitsch, Patrick Hennebelle, Tomoya Hirota, Melvin Hoare, Hiroshi Imai, Hideyuki Izumiura, Gilles Joncas, Paul Jones, Peter Kalberla, Ji-hyun Kang, Akiko Kawamura, Jürgen Kerp, Charles Kerton, Bon-Chul Koo, Roland Kothes, Stan Kurtz, Maša Laki´cevi´c, Tom Landecker, Alex Lazarian, Nadia Lo, Felix Lockman, Loris Magnani, Naomi McClure-Griffiths, Karl Menten, Victor Migenes, Marc-Antoine Miville-Deschênes, Erik Muller, Akiharu Nakagawa, Hiroyuki Nakanishi, Jun-ichi Nakashima, David Nidever, Lou Nigra, Josh Peek, Miguel Pérez-Torres, Chris Phillips, Mary Putman, Anthony Remijan, Philipp Richter, Peter arXiv:1009.0717v1 [astro-ph.GA] 3 Sep 2010 Schilke, Yoshiaki Sofue, Snežana Stanimirovi´c, Daniel Tafoya, Russ Taylor, Wen-Wu Tian, Lucero Uscanga, Jacco van Loon, Maxim Voronkov, Bart Wakker, Andrew Walsh, Tobias Westmeier, Benjamin Winkel, Ellen Zweibel The MagiKAT Team Gemma Bagheri, Amanda Bailey, Sudhanshu Barway,
    [Show full text]
  • Revealing the Ionization Properties of the Magellanic Stream Using Optical Emission
    The Astrophysical Journal, 851:110 (26pp), 2017 December 20 https://doi.org/10.3847/1538-4357/aa992a © 2017. The American Astronomical Society. All rights reserved. Revealing the Ionization Properties of the Magellanic Stream Using Optical Emission K. A. Barger1,2 , G. J. Madsen3, A. J. Fox4 , B. P. Wakker5 , J. Bland-Hawthorn6 , D. Nidever7 , L. M. Haffner8,9 , Jacqueline Antwi-Danso1,10, Michael Hernandez1, N. Lehner2 , A. S. Hill11,12 , A. Curzons6, and T. Tepper-García6 1 Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA 2 Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA 3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 4 Space Telescope Science Institute, Baltimore, MD 21218, USA 5 Supported by NASA/NSF, affiliated with Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706, USA 6 Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia 7 National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ, 85719, USA 8 Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706, USA 9 Space Science Institute, Boulder, CO 80301, USA 10 Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA 11 Departments of Physics and Astronomy, Haverford College, Haverford, PA 19041, USA 12 CSIRO Astronomy and Space Science, Marsfield, NSW 1710, Australia Received 2017 May 1; revised 2017 November 6; accepted 2017 November 6; published 2017 December 18 Abstract The Magellanic Stream, a gaseous tail that trails behind the Magellanic Clouds, could replenish the Milky Way (MW) with a tremendous amount of gas if it reaches the Galactic disk before it evaporates into the halo.
    [Show full text]
  • The Milky Way Almost Every Star We Can See in the Night Sky Belongs to Our Galaxy, the Milky Way
    The Milky Way Almost every star we can see in the night sky belongs to our galaxy, the Milky Way. The Galaxy acquired this unusual name from the Romans who referred to the hazy band that stretches across the sky as the via lactia, or “milky road”. This name has stuck across many languages, such as French (voie lactee) and spanish (via lactea). Note that we use a capital G for Galaxy if we are talking about the Milky Way The Structure of the Milky Way The Milky Way appears as a light fuzzy band across the night sky, but we also see individual stars scattered in all directions. This gives us a clue to the shape of the galaxy. The Milky Way is a typical spiral or disk galaxy. It consists of a flattened disk, a central bulge and a diffuse halo. The disk consists of spiral arms in which most of the stars are located. Our sun is located in one of the spiral arms approximately two-thirds from the centre of the galaxy (8kpc). There are also globular clusters distributed around the Galaxy. In addition to the stars, the spiral arms contain dust, so that certain directions that we looked are blocked due to high interstellar extinction. This dust means we can only see about 1kpc in the visible. Components in the Milky Way The disk: contains most of the stars (in open clusters and associations) and is formed into spiral arms. The stars in the disk are mostly young. Whilst the majority of these stars are a few solar masses, the hot, young O and B type stars contribute most of the light.
    [Show full text]