Chapter 3 the Interstellar Medium
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Dicke's Superradiance in Astrophysics
Western University Scholarship@Western Electronic Thesis and Dissertation Repository 9-1-2016 12:00 AM Dicke’s Superradiance in Astrophysics Fereshteh Rajabi The University of Western Ontario Supervisor Prof. Martin Houde The University of Western Ontario Graduate Program in Physics A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Fereshteh Rajabi 2016 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Physical Processes Commons, Quantum Physics Commons, and the Stars, Interstellar Medium and the Galaxy Commons Recommended Citation Rajabi, Fereshteh, "Dicke’s Superradiance in Astrophysics" (2016). Electronic Thesis and Dissertation Repository. 4068. https://ir.lib.uwo.ca/etd/4068 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract It is generally assumed that in the interstellar medium much of the emission emanating from atomic and molecular transitions within a radiating gas happen independently for each atom or molecule, but as was pointed out by R. H. Dicke in a seminal paper several decades ago this assumption does not apply in all conditions. As will be discussed in this thesis, and following Dicke's original analysis, closely packed atoms/molecules can interact with their common electromagnetic field and radiate coherently through an effect he named superra- diance. Superradiance is a cooperative quantum mechanical phenomenon characterized by high intensity, spatially compact, burst-like features taking place over a wide range of time- scales, depending on the size and physical conditions present in the regions harbouring such sources of radiation. -
Cyclotron Maser Emission in Solar and Stellar Flares 1
32nd URSI GASS, Montreal, 19–26 August 2017 CYCLOTRON MASER EMISSION IN SOLAR AND STELLAR FLARES Donald B. Melrose SIfA, School of Physics, University of Sydney, NSW 2006, Australia, http://www.physics.usyd.edu.au/ melrose 1 Introduction The problem discussed in this paper is whether the now accepted form of electron cyclotron maser emission (ECME) for the Earth’s auroral kilometric radiation (AKR) also applies to other suggested applications of ECME, which would have radical implications for solar and stellar applications, or whether AKR is an exception and a different form of ECME applies to other sources. Since circa 1980, ECME has been the accepted emission mechanism for AKR, for Jupiter’s decametric radiation (DAM), for solar spike bursts and for bright radio emission from flare stars. Originally, a loss-cone driven form of ECME [1] was widely accepted for all these application, but this changed for AKR in the 1990s when it was recognized that the driving electrons have a horseshoe distribution, and a horseshoe-driven form of ECME [2, 3] became the favored mechanism [13]. This form of ECME requires an extremely low electron density in the source region, in order for the radio emission to escape. This extreme condition appears to be satisfied in the “auroral cavity” that develops in association with the precipitating electrons [4]. The question discussed in this paper is whether the horseshoe-driven form of ECME, known to apply to AKR, applies to other sources of ECME, specifically to DAM, solar spike bursts and bright emission from flare stars. 2 Forms of ECME ECME corresponds to negative gyromagnetic absorption. -
Lifetimes of Interstellar Dust from Cosmic Ray Exposure Ages of Presolar Silicon Carbide
Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide Philipp R. Hecka,b,c,1, Jennika Greera,b,c, Levke Kööpa,b,c, Reto Trappitschd, Frank Gyngarde,f, Henner Busemanng, Colin Madeng, Janaína N. Ávilah, Andrew M. Davisa,b,c,i, and Rainer Wielerg aRobert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL 60605; bChicago Center for Cosmochemistry, The University of Chicago, Chicago, IL 60637; cDepartment of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637; dNuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550; ePhysics Department, Washington University, St. Louis, MO 63130; fCenter for NanoImaging, Harvard Medical School, Cambridge, MA 02139; gInstitute of Geochemistry and Petrology, ETH Zürich, 8092 Zürich, Switzerland; hResearch School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia; and iEnrico Fermi Institute, The University of Chicago, Chicago, IL 60637 Edited by Mark H. Thiemens, University of California San Diego, La Jolla, CA, and approved December 17, 2019 (received for review March 15, 2019) We determined interstellar cosmic ray exposure ages of 40 large ago. These grains are identified as presolar by their large isotopic presolar silicon carbide grains extracted from the Murchison CM2 anomalies that exclude an origin in the Solar System (13, 14). meteorite. Our ages, based on cosmogenic Ne-21, range from 3.9 ± Presolar stardust grains are the oldest known solid samples 1.6 Ma to ∼3 ± 2 Ga before the start of the Solar System ∼4.6 Ga available for study in the laboratory, represent the small fraction ago. -
Astronomy Astrophysics
A&A 432, 515–529 (2005) Astronomy DOI: 10.1051/0004-6361:20040331 & c ESO 2005 Astrophysics PAH charge state distribution and DIB carriers: Implications from the line of sight toward HD 147889, R. Ruiterkamp1,N.L.J.Cox2,M.Spaans3, L. Kaper2,B.H.Foing4,F.Salama5, and P. Ehrenfreund2 1 Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands e-mail: [email protected] 2 Institute Anton Pannekoek, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands 3 Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands 4 ESA Research and Scientific Support Department, PO Box 299, 2200 AG Noordwijk, The Netherlands 5 Space Science Division, NASA Ames Research Center, Mail Stop 245-6, Moffett Field, California 94035, USA Received 25 February 2004 / Accepted 29 September 2004 Abstract. We have computed physical parameters such as density, degree of ionization and temperature, constrained by a large observational data set on atomic and molecular species, for the line of sight toward the single cloud HD 147889. Diffuse interstellar bands (DIBs) produced along this line of sight are well documented and can be used to test the PAH hypothesis. To this effect, the charge state fractions of different polycyclic aromatic hydrocarbons (PAHs) are calculated in HD 147889 as a function of depth for the derived density, electron abundance and temperature profile. As input for the construction of these charge state distributions, the microscopic properties of the PAHs, e.g., ionization potential and electron affinity, are determined for a series of symmetry groups. The combination of a physical model for the chemical and thermal balance of the gas toward HD 147889 with a detailed treatment of the PAH charge state distribution, and laboratory and theoretical data on specific PAHs, allow us to compute electronic spectra of gas phase PAH molecules and to draw conclusions about the required properties of PAHs as DIB carriers. -
Physical Processes in the Interstellar Medium
Physical Processes in the Interstellar Medium Ralf S. Klessen and Simon C. O. Glover Abstract Interstellar space is filled with a dilute mixture of charged particles, atoms, molecules and dust grains, called the interstellar medium (ISM). Understand- ing its physical properties and dynamical behavior is of pivotal importance to many areas of astronomy and astrophysics. Galaxy formation and evolu- tion, the formation of stars, cosmic nucleosynthesis, the origin of large com- plex, prebiotic molecules and the abundance, structure and growth of dust grains which constitute the fundamental building blocks of planets, all these processes are intimately coupled to the physics of the interstellar medium. However, despite its importance, its structure and evolution is still not fully understood. Observations reveal that the interstellar medium is highly tur- bulent, consists of different chemical phases, and is characterized by complex structure on all resolvable spatial and temporal scales. Our current numerical and theoretical models describe it as a strongly coupled system that is far from equilibrium and where the different components are intricately linked to- gether by complex feedback loops. Describing the interstellar medium is truly a multi-scale and multi-physics problem. In these lecture notes we introduce the microphysics necessary to better understand the interstellar medium. We review the relations between large-scale and small-scale dynamics, we con- sider turbulence as one of the key drivers of galactic evolution, and we review the physical processes that lead to the formation of dense molecular clouds and that govern stellar birth in their interior. Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Straße 2, 69120 Heidelberg, Germany e-mail: [email protected], [email protected] 1 Contents Physical Processes in the Interstellar Medium ............... -
Laboratory Astrophysics: from Observations to Interpretation
April 14th – 19th 2019 Jesus College Cambridge UK IAU Symposium 350 Laboratory Astrophysics: From Observations to Interpretation Poster design by: D. Benoit, A. Dawes, E. Sciamma-O’Brien & H. Fraser Scientific Organizing Committee: Local Organizing Committee: Farid Salama (Chair) ★ P. Barklem ★ H. Fraser ★ T. Henning H. Fraser (Chair) ★ D. Benoit ★ R Coster ★ A. Dawes ★ S. Gärtner ★ C. Joblin ★ S. Kwok ★ H. Linnartz ★ L. Mashonkina ★ T. Millar ★ D. Heard ★ S. Ioppolo ★ N. Mason ★ A. Meijer★ P. Rimmer ★ ★ O. Shalabiea★ G. Vidali ★ F. Wa n g ★ G. Del-Zanna E. Sciamma-O’Brien ★ F. Salama ★ C. Wa lsh ★ G. Del-Zanna For more information and to contact us: www.astrochemistry.org.uk/IAU_S350 [email protected] @iaus350labastro 2 Abstract Book Scheduley Sunday 14th April . Pg. 2 Monday 15th April . Pg. 3 Tuesday 16th April . Pg. 4 Wednesday 17th April . Pg. 5 Thursday 18th April . Pg. 6 Friday 19th April . Pg. 7 List of Posters . .Pg. 8 Abstracts of Talks . .Pg. 12 Abstracts of Posters . Pg. 83 yPlenary talks (40') are indicated with `P', review talks (30') with `R', and invited talks (15') with `I'. Schedule Sunday 14th April 14:00 - 17:00 REGISTRATION 18:00 - 19:00 WELCOME RECEPTION 19:30 DINNER BAR OPEN UNTIL 23:00 Back to Table of Contents 2 Monday 15th April 09:00 { 10:00 REGISTRATION 09:00 WELCOME by F. Salama (Chair of SOC) SESSION 1 CHAIR: F. Salama 09:15 E. van Dishoeck (P) Laboratory astrophysics: key to understanding the Universe From Diffuse Clouds to Protostars: Outstanding Questions about the Evolution of 10:00 A. -
Review of Zeeman Effect Observations of Regions of Star Formation
Review of Zeeman Effect Observations of Regions of Star Formation Richard M. Crutcher 1,∗ and Athol J. Kemball 1 1Department of Astronomy, University of Illinois, Urbana, IL, USA Correspondence*: 1002 W. Green St., Urbana, IL 61801 USA [email protected] ABSTRACT The Zeeman effect is the only observational technique available to measure directly the strength of magnetic fields in regions of star formation. This chapter reviews the physics of the Zeeman effect and its practical use in both extended gas and in masers. We discuss observational results for the five species for which the Zeeman effect has been detected in the interstellar medium – H I, OH, and CN in extended gas and OH, CH3OH, and H2O in masers. These species cover a wide range in density, from ∼ 10 cm−3 to ∼ 1010 cm −3, which allows magnetic fields to be measured over the full range of cloud densities. However, there are significant limitations, including that only the line-of-sight component of the magnetic field strength can usually be measured and that there are often significant uncertainties about the physical conditions being sampled, particularly for masers. We discuss statistical methods to partially overcome these limitations. The results of Zeeman observations are that the mass to magnetic flux ratio, which measures the relative importance of gravity to magnetic support, is subcritical (gravity dominates 22 −2 magnetic support) at lower densities but supercritical for NH & 10 cm . Above nH ∼ 300 cm−3, which is roughly the density at which clouds typically become self-gravitating, the strength of magnetic fields increases approximately as B ∝ n2/3, which suggest that magnetic fields do not provide significant support at high densities. -
Radio Emission Toward Regions of Massive Star Formation in the Large Magellanic Cloud
Brigham Young University BYU ScholarsArchive Theses and Dissertations 2015-03-01 Radio Emission Toward Regions of Massive Star Formation in the Large Magellanic Cloud Adam Johanson Brigham Young University - Provo Follow this and additional works at: https://scholarsarchive.byu.edu/etd Part of the Astrophysics and Astronomy Commons, and the Physics Commons BYU ScholarsArchive Citation Johanson, Adam, "Radio Emission Toward Regions of Massive Star Formation in the Large Magellanic Cloud" (2015). Theses and Dissertations. 4419. https://scholarsarchive.byu.edu/etd/4419 This Dissertation is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Radio Emission Toward Regions of Massive Star Formation in the Large Magellanic Cloud Adam K. Johanson A dissertation submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Victor Migenes, Chair Clark G. Christensen Timothy W. Leishman J. Ward Moody Denise Stephens Department of Physics and Astronomy Brigham Young University March 2015 Copyright © 2015 Adam K. Johanson All Rights Reserved ABSTRACT Radio Emission Toward Regions of Massive Star Formation in the Large Magellanic Cloud Adam K. Johanson Department of Physics and Astronomy, BYU Doctor of Philosophy Four regions of massive star formation in the Large Magellanic Cloud (LMC) were observed for water and methanol maser emission and radio continuum emission. A total of 42 radio detec- tions were made including 27 new radio sources, four water masers, and eight compact H II regions. -
Interstellar Medium (ISM)
Interstellar Medium (ISM) Interstellar gas and dust Constituents of the ISM 60 40 15 Gas radiation field (CMB, ~ 1eV cm-3 various starlight, dust) ISM is very dilute, far from LTE Because the density of the ISM is extremely low, par>cles have a large mean free path 1 1 cm 3 λ 1015 − cm mfp ≈ n σ ≈ n H c H 3 Typical par>cle velocity: m v2 = k T 2 H B The collision >me scale is then: 1/2 1 λ T − n − τ 1.3 1011 H s c ≈ v ≈ × K 1 cm 3 − -3 Adop>ng T=100 K, nH=1 cm , we obtain about 1 collision in 500 years Local thermodynamic equilibrium (LTE) requires all species, including ions, electrons neutrals, and photons collide with each other sufficiently frequently. LTE applies inside the stars, NOT in the dilute ISM The mul>-phase interstellar gas • The various gas phases exist in pressure equilibrium: 3 4 3 n T 10 10 Kcm− · ≈ − (Kim et al. 1998) • The existence of a mul>-phase medium requires that energy flows through the system, e.g., by injec>on of energy through supernova explosions and/or stellar winds • The hot gas from SN explosions and stellar winds fills a large frac>on of the interstellar space, compressing the HI and molecular gas into a filamentary, fractal structure. Distribu>on of HI gas in the Large Magellanic Cloud Material Flow and Energy Balance of the ISM Infall from the 1 0.5M yr− intergalactic ∼ ⊙ Stars extragalactic medium gravitational and photons nuclear energies ISM 7 109M ∼ × ⊙ starlight stellar ejecta Star formation stellar winds photons kinetic energy 1 supernovae 1.3M yr− 1 ∼ ⊙ 0.5M yr− ISM ∼ ⊙ kinetic, thermal, chemical, STARS magnetic, gravitational and cosmic ray energies 1 0.2M yr− ∼ ⊙ radiative cooling stellar remnants extragalactic sky Abundance of elements in the solar neighborhood Hydrogen Asplund et al. -
Abiogenesis and Photostimulated Heterogeneous Reactions in The
Abiogenesis and Photostimulated Heterogeneous synthesize organic species in Interstellar Space on the Reactions in the Interstellar Medium and in the surface of dust particles (as they were on primitive Earth). Primitive Earth’s Atmosphere. Some peculiar features of heterogeneous photocatalytic Relevance to the Genesis of Life systems, namely (i) the considerable red shift of the spectral range of a given photoreaction compared with N. Serpone,1, 2 A. Emeline,1 V. Otroshchenko,3 one in homogeneous phase and (ii) the effect of spectral and V. Ryabchuk 4 selectivity of photocatalysts (5), favor the synthesis of 1 Department of Chemistry & Biochemistry, Concordia organic substrates under the above-mentioned natural University, Montreal (QC), Canada H3G 1M8. conditions. The first feature utilizes a considerably larger 2 Dipartimento di Chimica Organica, Universita di Pavia, fraction of Solar Energy than is otherwise possible in Pavia, Italia. homogeneous photochemical reactions. The second 3 Bach Institute of Biochemistry, Russian Academy of feature influences the dependence of the relative chemical Sciences, Moscow, Russia. yields of different products of a given reaction on the 4 Department of Physics, University of St.-Petersburg, wavelength of the actinic radiation. In particular, the St. Petersburg 198504, Russia. products of complete and partial oxidation of methane and other hydrocarbons result principally from the Studies of micrometeoritic particles captured by Earth photoexcitation of metal-oxide photocatalysts in the (i.e. ) absorption bands (strong at different geological times and discovered in Antarctica fundamental intrinsic have deduced that many organic substances necessary for absorption of UV and of blue light). More complex the Origin of Life on Earth are synthesized in Interstellar organic compounds are formed under irradiation of the catalysts in the absorption bands (weak to Space and are subsequently transported to Earth by extrinsic meteorites, comets, and cosmic dust (1). -
Cosmochemistry and the Origin of Life Proceedings of the NATO Advanced Study Institute Held at Maratea, Italy, June 1–12, 1981
C. Ponnamperuma (Ed.) Cosmochemistry and the Origin of Life Proceedings of the NATO Advanced Study Institute held at Maratea, Italy, June 1–12, 1981 Series: Nato Science Series C:, Vol. 101 For the first time in human history, developments in many branches of science provide us with an opportunity of formula ting a comprehensive picture of the universe from its beginning to the present time. It is an awesome reflection that the carbon in our bodies is the very carbon which was generated during the birth of a star. There is a perceptible continuum through the billions of years which can be revealed by the study of chemistry. Studies in nucleosynthesis have related the origin of the elements to the life history of the stars. The chemical elements we find on earth, HYdrogen, Carbon, Oxygen, and Nitrogen, were created in astronomical processes that took place in the past, and these elements are not spread throughout space in the form of stars and galaxies. Radioastronomers have discovered a vast array of organic molecules in the interstellar medium which have a bearing on prebiological chemical processes. Many of the molecules found so far contain 1983, VIII, 386 p. the four elements, C, N, 0, H. Except for the chem ically unreactive He, these four elements are the most abundant in the galaxy. The origin of polyatomic interstellar molecules is an unresolved problem. While we can explain the formation of some diatomic molecules Printed book as due to two atom collisions, it is much more difficult to form polyatomic molecules Hardcover by collisions between diatomic molecules and atoms. -
Search for Water and Life's Building Blocks in the Universe: an Introduction
Astronomy in Focus, Volume 1 XXIXth IAU General Assembly, August 2015 c 2015 International Astronomical Union Piero Benvenuti, ed. DOI: 00.0000/X000000000000000X Search for water and life’s building blocks in the Universe: An Introduction Sun Kwok1 1Faculty of Science, The University of Hong Kong, Hong Kong, China email: [email protected] Abstract. Water and organics are commonly believed to be the essential ingredients for life on Earth. The development of infrared and submillimeter observational techniques has resulted in the detection of water in circumstellar envelopes, interstellar clouds, comets, asteroids, planetary satellites and the Sun. Complex organics have also been found in stellar ejecta, diffuse and molecular clouds, meteorites, interplanetary dust particles, comets and planetary satellites. In this Focus Meeting, we will discuss the origin, distribution, and detection of water and other life’s building blocks both inside and outside of the Solar System. The possibility of extraterrestrial organics and water on the origin of life on Earth will also be discussed. Keywords. astrobiology, astrochemistry 1. Water in the Universe The water molecule was first discovered in space through its 616 − 523 rotational tran- sition at 22 GHz (Cheung et al. 1969). The inverted population and resultant maser emission of this transition allowed this line to be detected even in the early days of millimeter-wave receiver technology. Because of obscuration of the Earth’s atmosphere, the detection of the ground-state transition 557 GHz 110 − 101 of ortho-water has to wait until the development of satellite-based submillimeter telescopes. The 557 GHz line was first detected by SWAS and has been extensively observed in many astronomical sources by Odin and Herschel.