DOCSLIB.ORG

Studying the Local Interstellar Medium Through Measurements of Interstellar Hydrogen Inside the Heliosphere

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Studying the Local Interstellar Medium Through Measurements of Interstellar Hydrogen Inside the Heliosphere Master’s Thesis Theoretical Physics Studying The Local Interstellar Medium through Measurements of Interstellar Hydrogen Inside the Heliosphere Frida Wikberg November 9, 2020 Supervisors: Mika Juvela Erkki Kyrol¨ a¨ Examiners: Mika Juvela Erkki Kyrol¨ a¨ Karri Muinonen UNIVERSITY OF HELSINKI DEPARTMENT OF PHYSICS P.O. Box 64 (Gustaf Hallstr¨ omin¨ katu 2a) 00014 University of Helsinki Tiedekunta – Fakultet – Faculty Koulutusohjelma – Utbildningsprogram – Degree programme Faculty of Science Physical Sciences Tekijä – Författare – Author Frida Wikberg Työn nimi – Arbetets titel – Title Studying The Local Interstellar Medium through Measurements of Interstellar Hydrogen Inside the Heliosphere Työn laji – Arbetets art – Aika – Datum – Month and year Sivumäärä – Sidoantal – Number of pages Level November 9, 2020 50 Master’s thesis ​ ​ Tiivistelmä – Referat – Abstract The Interstellar Medium (ISM) incorporates all the matter that fills up the space between the stars of a galaxy. Interstellar matter consists mainly of hydrogen and helium gas, either in atomic or ionized form, as well as some heavier atoms, molecules and dust particles. It varies in temperature and density, forming structures and interacting with stars as a part of the stellar evolution. The Sun’s magnetic field and solar wind forms the heliosphere, effectively shielding us from our interstellar surroundings as we travel through the interstellar medium. However, the neutral component of the ISM, mainly in the form of hydrogen atoms, are not directly affected by the Sun’s magnetic field and can therefore enter the heliosphere where they can be observed through their interactions with solar Lyman-alpha photons that then produce the Lyman-alpha background radiation in the heliosphere. The SWAN instrument, on the SOHO satellite, measures this radiation and can provide a good picture of the interstellar hydrogen inside the heliosphere. In this work I introduce our current understanding of the Local ISM and ways of observing and modelling it. By modelling the intensity signal observed by SWAN, I also show an example of analysing interstellar parameters using SWAN observations of interstellar hydrogen inside the heliosphere. Avainsanat – Nyckelord – Keywords interstellar matter, heliosphere, local interstellar medium, SWAN, Lyman-alpha Säilytyspaikka – Förvaringställe – Where deposited Muita tietoja – Övriga uppgifter – Additional information Contents 1 Introduction 1 2 The Interstellar Medium 2 2.1 Origin and Structure . .2 2.1.1 The Origin of Matter . .2 2.1.2 Interstellar Constituents . .4 2.1.3 Interstellar Structures . .5 2.1.4 Observing the Interstellar Medium . .7 2.1.5 Interstellar Matter and Stellar Evolution . .9 2.2 The Local Interstellar Environment . 11 2.2.1 The Local Interstellar Bubble . 11 2.2.2 The Local Interstellar Cloud . 13 2.2.3 The Local Interstellar Magnetic Field . 16 2.2.4 The LIC-LB boundary . 16 2.2.5 Effect on Earth . 17 3 Interstellar Matter in the Heliosphere 19 3.1 The Solar Wind . 19 3.2 The Interplanetary Magnetic Field . 20 3.3 The Heliospheric Boundaries . 21 3.3.1 The Termination Shock . 22 3.3.2 The Heliopause . 23 CONTENTS 4 3.3.3 The Bow Shock . 24 3.4 The Interaction Between the Local Interstellar Medium and the Heliosphere . 25 3.4.1 Radiation and Gravity . 25 3.4.2 Charge Exchange and Pickup Ions . 25 4 The SWAN Instrument on SOHO 27 4.1 Solar Observations . 27 4.2 SOHO . 27 4.2.1 Scientific Objectives . 28 4.2.2 Success . 28 4.3 SWAN and the Lyman-a Method . 29 4.3.1 The Lyman-a method . 29 4.3.2 The SWAN Instrument . 31 4.3.3 A Typical SWAN Sky Map . 31 5 Modelling the Interstellar Matter in the Heliosphere 34 5.1 Challenges . 34 5.2 Early Models . 34 5.3 Multicomponent Models . 36 6 An Example Using Direct Simulation 37 6.1 Model for the intensity signal . 37 6.2 Parameters and data set used . 38 6.3 The Implementation . 38 6.4 Results . 39 6.5 Analysis . 42 7 Conclusions 45 1 INTRODUCTION 1 1 Introduction The interstellar medium (ISM) incorporates all the matter that fills up the space between the stars in a galaxy. From our point of view, the ISM begins at the edges of the solar wind’s influence and ends at the edges of the Galaxy where it meets the intergalactic medium. Interstellar matter consists mainly of hydrogen and helium gas, either in atomic or ionized form. Heavier atoms and molecules, dust particles, and cosmic rays make up some of the other constituents of interstellar space. Magnetic fields play an important role in the dynamics and overall structure of the ISM. Temperature and particle density vary over several orders of magnitude in different regions and form a diverse and complex environment far from the “empty space” it was once thought to be. Chapter 2 provides an introduction to the current knowledge of the interstellar matter in general and findings about our local interstellar environment in particular. The solar wind makes up nearly all the plasma content in interplanetary space. Eventually, far beyond the orbits of the planets, the solar wind comes to a stop and interstellar matter starts to dominate. This boundary marks the edge of the heliosphere. There are two very different types of plasmas interacting in this boundary region. On one hand we have the particles of the Local Interstellar Medium (LISM), particles of interstellar origin, and on the other there are the solar wind particles, ultimately originating from the protosolar cloud (PSC) that later became our solar system. Where these two plasmas meet, a dynamic and highly turbulent interface region is formed. In Chapter 3 the focus is on how the interstellar matter interacts with the Sun. The neutral particles of the LISM are not directly affected by the Sun’s magnetic field and so they can enter the heliosphere. Chapter 4 describes the observations made by the SWAN instrument on board the SOHO satellite, which can be used to study the interstellar particles flowing through and interacting with the heliosphere. Chapter 5 introduces the models used to describe these two multicomponent plasmas as well as their complex interactions. In Chapter 6, to exemplify this, I use a model of the interstellar H distribution in the heliosphere to simulate the Lyman-a observations made by SWAN in order to compare the two. The aim is to examine the behavior of the interstellar matter by looking at the characteristics and tendencies of the parameters when carefully varied. This is done using direct simulation. 2 The Interstellar Medium As interstellar space is highly complex and variable, it is of great importance to study the Local Interstellar Medium. The first part of this chapter describes what we know of interstellar space; what it consists of, how it is linked to stars, and how to study it. The second part deals with our local interstellar environment; the interstellar cloud that the Sun is immersed in and the large interstellar bubble surrounding that cloud. 2.1 Origin and Structure The widely accepted theory of cosmology describing the origin of the Universe can be summed up in the Big Bang model. Observations verify that we live in a Universe that was once extremely hot, dense, and concentrated to a single spot from where the Big Bang caused it to start expanding. Hydrogen and helium were formed only a few minutes after the bang and remain to this day the two most abundant elements in the known Universe. Interstellar matter is inhomogeneously spread out. Approximately half of the interstellar mass in the Galaxy is situated in relatively dense structures, called interstellar clouds, taking up only 1 − 2% of the volume of interstellar space. Consequently, the low-density regions form massive cavities, bubbles, in the ISM. In a clear sky, the ISM can be seen as darker regions, mainly along the Milky Way, where clouds of interstellar particles absorb the light from stars behind them. The main method for studying the ISM is spectroscopy. The chemical composition of stars as well as the matter surrounding the stars can be deduced by analyzing spectral lines of emission or absorption. Stars interact with the ISM in several ways. A star is born as a result of a very dense cloud collapsing and during its life cycle it will itself emit matter into interstellar space. If it dies in a supernova it will end up having a profound effect on its surroundings. 2.1.1 The Origin of Matter A few minutes after the Big Bang, 13:8 billion years ago, the process called primordial nucleosynthesis began. Nucleosynthesis is the fusion process in which free protons and neutrons are combined to form nuclei. This resulted in the two lightest, most elemental nuclei; that of hydrogen and helium, and some 2 2 THE INTERSTELLAR MEDIUM 3 of their isotopes. Very small amounts of beryllium (Be) and lithium (Li) nuclei are also thought to have formed at this point. Along with photons, they are the only particles in existence at this time in the early Universe. At an approximate age of 105 years, due to the ongoing inflation, the density and temperature of the Universe reached values low enough to allow for the process of recombination, in which the nuclei capture electrons to form the first atoms. At roughly 109 years, the inhomogeneity of space finally resulted in the gravitational collapse of matter into stars. These first stars are categorized as population III stars. All elements, except for the ones created during the nucleosynthesis, are produced by stars. Galaxies and clusters develop later as an effect of gravitational collapse on a larger scale. At this point, stars that may contain traces of already star-processed material started appearing. They are population II stars, and later on, stars of population I arose.
Load more

Recommended publications
  • Arxiv:Astro-Ph/0702596V3 25 May 2007 Nieo H Eishr,I N Lulti O Est IS Towa Density Direction Low Upwind an a Has in Fluff Cloudlet Local the One Fluff
    The Local Bubble and Interstellar Material Near the Sun P. C. Frisch1,∗ 1Dept. of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, USA (∗Author for correspondence, Email: [email protected]) Abstract. The properties of interstellar matter at the Sun are regulated by our location with respect to a void in the local matter distribution, known as the Local Bubble. The Local Bubble (LB) is bounded by associations of massive stars and fossil supernovae that have disrupted dense interstellar matter (ISM), driving low density intermediate velocity ISM into the void. The Sun appears to be located in one of these flows of low density material. This nearby interstellar matter, dubbed the Local Fluff, has a bulk velocity of ∼ 19 km s−1 in the local standard of rest. The flow is coming from the direction of the gas and dust ring formed where the Loop I supernova remnant merges into the LB. Optical polarization data suggest the local interstellar magnetic field lines are draped over the heliosphere. A longstanding discrepancy between the high thermal pressure of plasma filling the LB and low thermal pressures in the embedded Local Fluff cloudlets is partially mitigated when the ram pressure component parallel to the cloudlet flow direction is included. Keywords: ISM: general, ISM: abundances 1. Introduction The existence of an area clear of interstellar material around the Sun, now known as the Local Bubble, was discovered as an underdense region in measurements of starlight reddening (Fitzgerald, 1968). This underdense region is traced by color excess measurements showing E(B − V )< 0.01 mag,1 and extends beyond 100 pc in the galactic longitude interval ℓ = 180◦ − 270◦.
    [Show full text]
  • Arxiv:Astro-Ph/0702596V1 22 Feb 2007
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server The Local Bubble and Interstellar Material Near the Sun P. C. Frisch1,∗ 1Dept. of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, USA (∗Author for correspondence, Email: [email protected]) Abstract. The properties of interstellar matter (ISM) at the Sun are regulated by our location with respect to the Local Bubble (LB) void in the ISM. The LB is bounded by associations of massive stars and fossil supernovae that have disrupted natal ISM and driven intermediate velocity ISM into − the LB interior void. The Sun is located in such a driven ISM parcel, which is low density (< 10 24.2 − − g cm 3). The Local Fluff has a bulk velocity of ∼ 19 km s 1 in the LSR, and an upwind direction at the center of the gas and dust ring formed by the Loop I supernova remnant interaction with the LB. Radiative transfer models give the properties of the Local Interstellar Cloud, LIC, at the heliosphere. The mystery of missing pressure is solved when the ram pressure of the LIC is included in the total LIC pressure. In this case, and if magnetic thermal and cosmic ray pressures are similar in the LIC, the LIC appears to be in pressure equilibrium with the plasma in the local hot bubble. Keywords: ISM: general, ISM: abundances 1. Introduction The existence of an area clear of interstellar material around the Sun, now known as the Local Bubble, was discovered as an underdense region in measurements of starlight reddening (Fitzgerald, 1968).
    [Show full text]
  • [Astro-Ph.GA] 15 Oct 2015 Nt Eatooi,Gosc Inisamseia,Uni Atmosfericas, Ciencias E Geofisica Astronomia, De Inst
    Submitted to Astrophysical Journal June 24, 2015 Charting the Interstellar Magnetic Field causing the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms P. C. Frisch Dept. Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 A. Berdyugin and V. Piirola Finnish Centre for Astronomy with ESO, University of Turku, Finland A. M. Magalhaes and D. B. Seriacopi Inst. de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Brazil S. J. Wiktorowicz Dept. Astronomy, University of California at Santa Cruz, Santa Cruz, CA B-G Andersson SOFIA Science Center, USRA, Moffett Field, CA H. O. Funsten Los Alamos National Laboratory, Los Alamos, NM D. J. McComas1 Southwest Research Institute, San Antonio, TX arXiv:1510.04679v1 [astro-ph.GA] 15 Oct 2015 N. A. Schwadron Space Science Center, University of New Hampshire J. D. Slavin Harvard-Smithsonian Center for Astrophysics, Cambridge, MA A. J. Hanson 1Also University of Texas, San Antonio, TX –2– School of Informatics and Computing, Indiana University, Bloomington, IN C.-W. Fu School of Computer Engineering, Nanyang Technological University, Singapore ABSTRACT The interstellar magnetic field (ISMF) near the heliosphere is a fundamen- tal component of the solar galactic environment that can only be studied using polarized starlight. The results of an ongoing survey of the linear polarizations of local stars are analyzed with the goal of linking the interstellar magnetic field that shapes the heliosphere to the nearby field in interstellar space. We present new results on the direction of the magnetic field within 40 pc obtained from analyzing polarization data using a merit function that determines the field di- rection that provides the best fit to the polarization data.
    [Show full text]
  • Interaction of the Local Bubble with Its Environment
    Interaction of the Local Bubble with its environment Roland Egger Max-Planck-Institut fur extraterrestrische Physik, Giessenbachstrasse, D-85740 Garching, Germany Abstract. The Local Bubble (LB), a volume of roughly 100 pc radius filled with ionized gas of high temperature and low density, is not a unique object. It is obvi­ ously surrounded by several interstellar bubbles of similar properties. Some of them are as close as to undergo interaction with the LB. Our most prominent neighbour is the Loop I superbubble formed by the Sco-Cen OB association. It is shown that this huge shell is in collision with our Local Bubble. The product of this interaction is an annular cloud of dense neutral gas at the boundary between the two bubbles. Other examples for close neighbouring bubbles are the Gum nebula, the Eridanus bubble and possibly the two radio loops II and III. 1 Introduction The structure of the diffuse soft X-ray background (SXRB, E < 2 keV) has been subject to controversial discussion ever since its discovery by Bowyer et al. (1968). On the one hand there is a very soft (C-band, < 0.3 keV) component which is more or less isotropic at low galactic latitudes (b < 30°). This component is obviously not absorbed by any intervening neutral gas with column densities above NH = 1019cm-2 and therefore, attributable to a local diffuse X-ray source, most probably highly ionized gas filling the Local Bubble (LB). The properties and possible origin of this local interstellar bubble have been determined, modelled and discussed by various authors. A recent review is given by Breitschwerdt (1996) and Breitschwerdt et al.
    [Show full text]
  • THE INTERSTELLAR MEDIUM (ISM) • Total Mass ~ 5 to 10 X 109 Solar Masses of About 5 – 10% of the Mass of the Milky Way Galaxy Interior to the SunS Orbit
    THE INTERSTELLAR MEDIUM (ISM) • Total mass ~ 5 to 10 x 109 solar masses of about 5 – 10% of the mass of the Milky Way Galaxy interior to the suns orbit • Average density overall about 0.5 atoms/cm3 or ~10-24 g cm-3, but large variations are seen The Interstellar Medium • Elemental Composition - essentially the same as the surfaces of Population I stars, but the gas may be ionized, neutral, or in molecules or dust. H I – neutral atomic hydrogen http://apod.nasa.gov/apod/astropix.html H2 - molecular hydrogen H II – ionized hydrogen He I – neutral helium Carbon, nitrogen, oxygen, dust, molecules, etc. THE INTERSTELLAR MEDIUM • Energy input – starlight (especially O and B), supernovae, cosmic rays • Cooling – line radiation from atoms and molecules and infrared radiation from dust • Largely concentrated (in our Galaxy) in the disk Evolution in the ISM of the Galaxy As a result the ISM is continually stirred, heated, and cooled – a dynamic environment, a bit like the Stellar winds earth’s atmosphere but more so because not gravitationally Planetary Nebulae confined Supernovae + Circulation And its composition evolves as the products of stellar evolution are mixed back in by stellar winds, supernovae, etc.: Stellar burial ground metal content The The 0.02 Stars Interstellar Big Medium Galaxy Bang Formation star formation White Dwarfs and Collisions Neutron stars Black holes of heavy elements fraction Total Star Formation 10 billion Time years The interstellar medium (hereafter ISM) was first discovered in 1904, with the observation of stationary calcium absorption lines superimposed on the Doppler shifting spectrum of a spectroscopic binary.
    [Show full text]
  • Lawrence Berkeley National Laboratory Recent Work
    Lawrence Berkeley National Laboratory Recent Work Title QUASI-PERIODIC COMET SHOWERS AND MASS EXTINCTIONS BY SUPERSHELL PASSAGE Permalink https://escholarship.org/uc/item/30f4801d Authors Carroll, J. Kolehmaninen, K. Karant, Y. Publication Date 1988-06-01 eScholarship.org Powered by the California Digital Library University of California LBL-25379 c. d­ Preprint Lawrence Berkeley ·Laboratory UNIVERSITY OF CALIFORNIA REC!SI\...__ LAlNREi'JCE :': ....... t":; ~vI 6~0Pt-T~· "'If:;~- - 198C- u Submitted to Nature U2f1P.:~y AND _:,:.:~·~-~~l'!TS S!::s~·: . Quasi-periodic Comet Showers and Mass Extinctions by Supershell Passage J. Carroll, K. Kolehmaninen, andY. Karant June 1988 TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. Prepared for the U.S. Department of Energy under Contract Numh~r DE-AC03-76SF00098. DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California.
    [Show full text]
  • Observations of Magnetic Fields - J.P
    Observations of Magnetic Fields - J.P. Vallée file:///e:/moe/HTML/March03/Vallee/paper.html Published in "Fundamentals of Cosmic Physics", Vol. 19, pp. 1-89, 1997. Observations of the Magnetic Fields inside and outside the Milky Way, starting with Globules (~ 1 parsec), Filaments, Clouds, SuperBubbles, Spiral Arms, Galaxies, Superclusters, and ending with the Cosmological Universe's Background Surface (at ~ 8 Teraparsecs) Jacques P. Vallée Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, B.C., Canada V8X 4M6 Abstract. The observational study of galactic magnetic fields dates back to 1949; an excellent review of the early 30 years has been made by Verschuur (1979). I review here the developments since then and the current state of our observational knowledge on the magnetic fields inside and outside the Milky Way galaxy, for objects with sizes greater than 1 parsec (= 3.2 light-years; = 3.1 × 1016 m). Included are the medium-scale magnetic fields in the isolated globules, dusty elongated clouds and narrow filaments, large interstellar superbubbles, and in large-scale magnetic fields in the spiral arms in our Galaxy and in objects outside our Galaxy out to cosmological distances. The large-scale magnetic fields can act as guides to the low density gas in its motion in the rarefied areas of the interstellar medium, and as tracers of the past dynamical histories of galaxies in motion, linking galactic dynamic with galactic dynamos. Medium-scale magnetic fields can play a support role, supporting clouds against outside pressures or against collapse due to self-gravity. Small-scale magnetic fields play a significant role on smaller-scale phenomena: propagation of cosmic-rays, shock waves, cosmic dust orientation, star formation (although there is little detailed discussion here of magnetic fields on star formation and objects with sizes < 1 parsec).
    [Show full text]
  • Highly Ionized Gas in the Local ISM: Some Like It Hot? B.-Y
    Highly ionized gas in the Local ISM: Some like it hot? B.-Y. Welsh, Rosine Lallement To cite this version: B.-Y. Welsh, Rosine Lallement. Highly ionized gas in the Local ISM: Some like it hot?. Astronomy and Astrophysics - A&A, EDP Sciences, 2005, 436, pp.615-632. 10.1051/0004-6361:20042611. hal- 00077971 HAL Id: hal-00077971 https://hal.archives-ouvertes.fr/hal-00077971 Submitted on 11 Feb 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. A&A 436, 615–632 (2005) Astronomy DOI: 10.1051/0004-6361:20042611 & c ESO 2005 Astrophysics Highly ionized gas in the local ISM: Some like it hot? B. Y. Welsh1 and R. Lallement2 1 Experimental Astrophysics Group, Space Sciences Laboratory, UC Berkeley, Berkeley, CA 94720, USA e-mail: [email protected] 2 Service d’Aéronomie du CNRS, 91371 Verrières-le-Buisson, France Received 23 December 2004 / Accepted 18 February 2005 Abstract. We present HST-STIS medium-resolution spectra (R ∼ 6.5kms−1) of the ultraviolet interstellar absorption lines observed towards 4 early-type stars located within the local interstellar medium (ISM), with sight-line distances <186 pc in the general direction of the Loop I superbubble (l = 330◦, b =+18◦).
    [Show full text]
  • A Nearby Recent Supernova That Ejected the Runaway Star Ζ Oph, the Pulsar PSR B1706-16, and 60Fe Found on Earth
    MNRAS 000,1{ ?? (2019) Preprint 17 September 2019 Compiled using MNRAS LATEX style file v3.0 A nearby recent supernova that ejected the runaway star ζ Oph, the pulsar PSR B1706-16, and 60Fe found on Earth R. Neuh¨auser,1?, F. Gießler1, and V.V. Hambaryan1;2 1Astrophysikalisches Institut und Universit¨ats-Sternwarte Jena, Schillerg¨aßchen 2-3, 07745 Jena, Germany 2Byurakan Astrophysical Observatory, Byurakan 0213, Aragatzotn, Armenia Accepted XXX. Received XXX; in original form July 2019 ABSTRACT The detection of 1:5 3:2 Myr old 60Fe on Earth indicates recent nearby core-collapse supernovae. For∼ supernovae− in multiple stars, the primary stars may become neutron stars, while former companions may become unbound and become runaway stars. We wrote software for tracing back the space motion of runaway and neutron stars to young associations of massive stars. We apply it here to the nearby young Scorpius- Centaurus-Lupus groups, all known runaway stars possibly coming from there, and all 400 neutron stars with known transverse velocity. We find kinematic evidence that the runaway ζ Oph and the radio pulsar PSR B1706-16 were released by a supernova in a binary 1:78 0:21 Myr ago at 107 4 pc distance (for pulsar radial velocity 260 43 km/s); association± age and flight± time determine the progenitor mass (16-18 M± ), which can constrain supernova nucleosynthesis yields and 60Fe uptake on Earth. In addition, we notice that the only high-mass X-ray binary in Scorpius-Centaurus-Lupus (1H11255-567 with µ1 and µ2 Cru) may include a neutron star formed in another SN, up to 1:8 Myr ago at 89 112 pc, i.e.
    [Show full text]
  • THE INTERSTELLAR MEDIUM • Total Mass ~ 5 to 10 X 109 Solar Masses of About 5 – 10% of the Mass of the Milky Way Galaxy Interior to the SunS Orbit
    THE INTERSTELLAR MEDIUM • Total mass ~ 5 to 10 x 109 solar masses of about 5 – 10% of the mass of the Milky Way Galaxy interior to the suns orbit • Average density overall about 0.5 atoms/cm3 or ~10-24 g cm-3, but large variations are seen The Interstellar Medium • Composition - essentially the same as the surfaces of Population I stars, but the gas may be ionized, neutral, or in molecules (or dust) H I – neutral atomic hydrogen http://apod.nasa.gov/apod/astropix.html H2 - molecular hydrogen H II – ionized hydrogen He I – neutral helium Carbon, nitrogen, oxygen, dust, molecules, etc. Evolution in the ISM of the Galaxy THE INTERSTELLAR MEDIUM Stellar winds Planetary Nebulae Supernovae + Circulation • Energy input – starlight (especially O and B), supernovae, cosmic rays Stellar burial ground • Cooling – line radiation and infrared radiation The The Stars Interstellar Big from dust Medium Galaxy Bang Formation • Largely concentrated (in our Galaxy) in the disk White Dwarfs Neutron stars Black holes Star Formation As a result the ISM is continually stirred, heated, and cooled – a dynamic environment And its composition evolves: 0.02 Total fraction of heavy elements Total 10 billion Time years THE LOCAL BUBBLE Scorpius-Centaurus Asociation http://www.daviddarling.info/encyclopedia/L/Local_Bubble.html (the Loop 1 Bubble) The “Local Bubble” is a region of low density (~0.05 cm-3 and • Nearest OB association to sun. Distance 400 to 500 ly Loop I bubble high temperature (~106 K) Contains many of the bright blue stars in the constellations 600 ly has been inflated by numerous Scorpius, Antares, and Lupus, including as its brightest supernova explosions.
    [Show full text]
  • Highly Ionized Gas in the Local ISM: Some Like It Hot?
    A&A 436, 615–632 (2005) Astronomy DOI: 10.1051/0004-6361:20042611 & c ESO 2005 Astrophysics Highly ionized gas in the local ISM: Some like it hot? B. Y. Welsh1 and R. Lallement2 1 Experimental Astrophysics Group, Space Sciences Laboratory, UC Berkeley, Berkeley, CA 94720, USA e-mail: [email protected] 2 Service d’Aéronomie du CNRS, 91371 Verrières-le-Buisson, France Received 23 December 2004 / Accepted 18 February 2005 Abstract. We present HST-STIS medium-resolution spectra (R ∼ 6.5kms−1) of the ultraviolet interstellar absorption lines observed towards 4 early-type stars located within the local interstellar medium (ISM), with sight-line distances <186 pc in the general direction of the Loop I superbubble (l = 330◦, b =+18◦). These data have been supplemented with high resolution (R ∼ 3kms−1) visible absorption observations of the NaI D-lines towards these 4 stars. Our main discovery is the detection of highly ionized absorption components of CIV, SiIV and NV towards the two most distant targets, HD 127381 and HD 142256. These lines-of-sight are known to cross both the near and far neutral interface boundaries to the Loop I cavity, in addition to intersecting the fragmented shell of neutral and partially ionized gas that defines the boundary to the Local Bubble. However, the presently measured narrow line profile-widths and their measured absorption intensities are found to be incompatible with theoretical models that predict high ion absorption due to the presence of evaporating cloud conduction interfaces. We conclude that the formation of high ions in the local ISM is highly dependent on the location of the absorbing gas clouds with respect to nearby sources of both hot X-ray emitting gas and/or photo-ionization.
    [Show full text]
  • 1. Introduction
    THE ASTROPHYSICAL JOURNAL, 545:290È300, 2000 December 10 ( 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A. DISTANCE LIMITS ON THE BRIGHT X-RAY EMISSION TOWARD THE GALACTIC CENTER: EVIDENCE FOR A VERY HOT INTERSTELLAR MEDIUM IN THE GALACTIC X-RAY BULGE R. C. ALMY AND D. MCCAMMON Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, WI 53706; almy=wisp5.physics.wisc.edu, mccammon=wisp.physics.wisc.edu S. W. DIGEL Raytheon STX, NASA/Goddard Space Flight Center, Code 660.2, Greenbelt, MD 20771; digel=gsfc.nasa.gov AND L. BRONFMAN AND J. MAY Universidad de Chile, Departamento de Astronomia, Casilla 36-D, Santiago, Chile; leo=das.uchile.cl, jmay=das.uchile.cl Received 1998 July 13; accepted 2000 July 25 ABSTRACT 3 Observations of the di†use X-ray background at energiesD4 and 1.5 keV show a large region of enhanced emission around the Galactic center. The origin of this X-ray enhancement is not known, but the best candidates are the nearby Loop I superbubble and a Galactic X-ray bulge. To di†erentiate between these two possibilities, the distance scales to the X-rayÈemitting material along the line of sight must be established. A mosaic of 13 ROSAT PSPC pointings in the direction of l D 337¡, b D 4¡ reveals 3 X-ray shadows in the4 and 1.5 keV bands cast by a distant molecular cloud complex. Analysis of the shadows indicates that a large fraction (45% ^ 9%) of the observed emission in this direction originates beyond the cloud complex, located at d D 2 kpc.
    [Show full text]