The Emission Lines of Quasars and Similar Objects
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Stark Broadening of Spectral Lines in Plasmas
atoms Stark Broadening of Spectral Lines in Plasmas Edited by Eugene Oks Printed Edition of the Special Issue Published in Atoms www.mdpi.com/journal/atoms Stark Broadening of Spectral Lines in Plasmas Stark Broadening of Spectral Lines in Plasmas Special Issue Editor Eugene Oks MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade Special Issue Editor Eugene Oks Auburn University USA Editorial Office MDPI St. Alban-Anlage 66 4052 Basel, Switzerland This is a reprint of articles from the Special Issue published online in the open access journal Atoms (ISSN 2218-2004) in 2018 (available at: https://www.mdpi.com/journal/atoms/special issues/ stark broadening plasmas) For citation purposes, cite each article independently as indicated on the article page online and as indicated below: LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. Journal Name Year, Article Number, Page Range. ISBN 978-3-03897-455-0 (Pbk) ISBN 978-3-03897-456-7 (PDF) Cover image courtesy of Eugene Oks. c 2018 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND. Contents About the Special Issue Editor ...................................... vii Preface to ”Stark Broadening of Spectral Lines in Plasmas” ..................... ix Eugene Oks Review of Recent Advances in the Analytical Theory of Stark Broadening of Hydrogenic Spectral Lines in Plasmas: Applications to Laboratory Discharges and Astrophysical Objects Reprinted from: Atoms 2018, 6, 50, doi:10.3390/atoms6030050 ................... -
Chapter 3 the Mechanisms of Electromagnetic Emissions
BASICS OF RADIO ASTRONOMY Chapter 3 The Mechanisms of Electromagnetic Emissions Objectives: Upon completion of this chapter, you will be able to describe the difference between thermal and non-thermal radiation and give some examples of each. You will be able to distinguish between thermal and non-thermal radiation curves. You will be able to describe the significance of the 21-cm hydrogen line in radio astronomy. If the material in this chapter is unfamiliar to you, do not be discouraged if you don’t understand everything the first time through. Some of these concepts are a little complicated and few non- scientists have much awareness of them. However, having some familiarity with them will make your radio astronomy activities much more interesting and meaningful. What causes electromagnetic radiation to be emitted at different frequencies? Fortunately for us, these frequency differences, along with a few other properties we can observe, give us a lot of information about the source of the radiation, as well as the media through which it has traveled. Electromagnetic radiation is produced by either thermal mechanisms or non-thermal mechanisms. Examples of thermal radiation include • Continuous spectrum emissions related to the temperature of the object or material. • Specific frequency emissions from neutral hydrogen and other atoms and mol- ecules. Examples of non-thermal mechanisms include • Emissions due to synchrotron radiation. • Amplified emissions due to astrophysical masers. Thermal Radiation Did you know that any object that contains any heat energy at all emits radiation? When you’re camping, if you put a large rock in your campfire for a while, then pull it out, the rock will emit the energy it has absorbed as radiation, which you can feel as heat if you hold your hand a few inches away. -
The Protection of Frequencies for Radio Astronomy 1
JOURNAL OF RESEARCH of the National Bureau of Standards-D. Radio Propagation Vol. 67D, No. 2, March- April 1963 b The Protection of Frequencies for Radio Astronomy 1 R. 1. Smith-Rose President, International Scientific Radio Union (R eceived November 5, 1962) The International T elecommunications Union in its Geneva, 1959 R adio R egulations r recognises the Radio Astronomy Service in t he two following definitions: N o. 74 Radio A st1" onomy: Astronomy based on t he reception of waves of cos mi c origin. No. 75 R adio A st1"onomy Se1"vice: A service involving the use of radio astronomy. This service differs, however, from other r adio services in two important respects. 1. It does not itself originate any radio waves, and therefore causes no interference to any other service. L 2. A large proportion of its activity is conducted by the use of reception techniques which are several orders of magnit ude )]).ore sensitive than those used in other ra dio services. In order to pursue his scientific r esearch successfully, t he radio astronomer seeks pro tection from interference first, in a number of bands of frequencies distributed t hroughout I t he s p ~ct run:; and secondly:. 1~10r e complete and s p ec i~c prote.ction fOl: t he exact frequency bands III whIch natural radIatIOn from, or absorptIOn lD, cosmIc gases IS known or expected to occur. The International R egulations referred to above give an exclusive all ocation to one freq uency band only- the emission line of h ydrogen at 1400 to 1427 Mc/s. -
Doppler-Free Spectroscopy
Doppler-Free Spectroscopy MIT Department of Physics (Dated: November 29, 2012) Traditionally, optical spectroscopy had been performed by dispersing the light emitted by excited matter, or by dispersing the light transmitted by an absorber. Alternatively, if one has available a tunable monochromatic source (such as certain lasers), a spectrum can be measured one wave- length at a time' by measuring light intensity (fluorescence or transmission) as a function of the wavelength of the tunable source. In either case, physically important structures in such spectra are often obscured by the Doppler broadening of spectral lines that comes from the thermal motion of atoms in the matter. In this experiment you will make use of an elegant technique known as Doppler-free saturated absorption spectroscopy that circumvents the problem of Doppler broaden- ing. This experiment acquaints the student with saturated absorption laser spectroscopy, a common application of non-linear optics. You will use a diode laser system to measure hyperfine splittings 2 2 85 87 in the 5 S1=2 and 5 P3=2 states of Rb and Rb. I. PREPARATORY PROBLEMS II. LASER SAFETY 1. Suppose you are interested in small variations in You will be using a medium low power (≈ 40 mW) wavelength, ∆λ, about some wavelength, λ. What near-infrared laser in this experiment. The only real is the expression for the associated small variations damage it can do is to your eyes. Infrared lasers are es- in frequency, ∆ν? Now, assuming λ = 780nm (as is pecially problematic because the beam is invisible. You the case in this experiment), what is the conversion would be surprised how frequently people discover they factor between wavelength differences (∆λ) and fre- have a stray beam or two shooting across the room. -
1 Spectroscopic Study of Unique Line Broadening and Inversion in Low
Spectroscopic study of unique line broadening and inversion in low pressure microwave generated water plasmas R. L. Mills,a) P. C. Ray, R. M. Mayo, M. Nansteel, B. Dhandapani BlackLight Power, Inc., 493 Old Trenton Road, Cranbury, NJ 08512 Jonathan Phillips University of New Mexico, Dept. of Chemical and Nuclear Engineering, 203 Farris Engineering, Albuquerque, NM 87131 It was demonstrated that low pressure (~ 0.2 Torr) water vapor plasmas generated in a 10 mm inner diameter quartz tube with an Evenson microwave cavity show at least two features which are not explained by conventional plasma models. First, significant (> 2.5 Å) hydrogen Balmer α line broadening, of constant width, up to 5 cm from the microwave coupler was recorded. Only hydrogen, and not oxygen, showed significant line broadening. This feature, observed previously in hydrogen-containing mixed gas plasmas generated with high voltage dc and rf discharges was explained by some researchers to result from acceleration of hydrogen ions near the cathode. This explanation cannot apply to the line broadening observed in the (electrodeless) microwave plasmas generated in this work, particularly at distances as great as 5 cm from the microwave coupler. Second, inversion of the line intensities of both the Lyman and Balmer series, again, at distances up to 5 cm from the coupler, were observed. The line inversion suggests the existence of a hitherto unknown source of pumping of the 1 optical power in plasmas. Finally, it is notable that other aspects of the plasma including the OH* rotational temperature and low electron concentrations are quite typical of plasmas of this type. -
The Radio-Frequency Line Spectrum of Atomic Hydrogen and Its Applications in Astronomy
THE RADIO-FREQUENCY LINE SPECTRUM OF ATOMIC HYDROGEN AND ITS APPLICATIONS IN ASTRONOMY J. P. Wild Division of Radiophysics, Commonwealth Scientific and Industrial Research Organization, Australia Received September 8, 1951 ABSTRACT Formulae are obtained for the frequencies, transition probabilities, and natural widths of the dis- crete lines of atomic hydrogen that fall within the radio spectrum. Such lines are due to transitions within either the fine structure or the hyperfine structure of the energy levels. The conditions necessary for the formation of observable emission and absorption lines are examined. Thence an inquiry is made into which of the hydrogen lines are likely to be observable from astronomi- cal systems. It is found that the sun may give a detectable absorption line at about 10,000 Mc/sec, corre- 2 2 sponding to the 2 Si/2-2 P3/2 fine-structure transition, but that other solar fines are not likely to be observable. From the interstellar gas, the emission line already observed (i.e., the 1420 Mc/sec hyper- fine-structure line) is probably the only detectable hydrogen line. The importance of this fine in the study of the interstellar gas is discussed. Some general conclusions are drawn from the preliminary evidence regarding the motion and kinetic temperature of the regions of un-ionized hydrogen. The ratio data are used to obtain a measure of the product of “galactic thickness” and average hydrogen concentration. I. INTRODUCTION The first astronomical observation of a spectral line in the radio-frequency band has recently been announced by Ewen and Purcell1 and has had independent confirmation by two other groups of workers.2,3 The observed line is an emission line of frequency 1420 Mc/sec due to the transition between the hyperfine-s truc ture substates in the ground state of atomic hydrogen. -
Spectra of Photoionized Regions 1. Introduction
Spectra of Photoionized Regions Friday, January 21, 2011 CONTENTS: 1. Introduction 2. Recombination Processes A. Overview B. Level networks C. Free-bound continuum D. Two-photon continuum E. Collisions 3. Additional Processes A. Lyman-α emission B. Helium processes C. Resonance fluorescence 4. Diagnostics A. Temperature B. Density C. Composition D. Star formation rates 1. Introduction Our next task is to consider the emitted spectrum from an H II region. This is one of the most important subjects observationally since spectroscopy provides our principal set of diagnostics on the physics occurring in the region. This material is (mostly) covered in Chapters 4 and 5 of Osterbrock & Ferland (on which most of these notes are based). The sources of emission we will consider fall into two categories: Cooling: Infrared fine structure lines Optical forbidden lines Free-free continuum Recombination: Free-bound continuum Recombination lines Two-photon continuua 1 Generally, the forbidden lines (optical or IR) come from metals, whereas the recombination features are proportional to abundance and arise mainly from H and He. Since the cooling radiation has already been discussed, we will focus on recombination and then proceed to diagnostics. 2. Recombination Processes A. OVERVIEW We first consider the case of recombination of hydrogen at very low densities where the collision rates are small, i.e. any hydrogen atom that forms can decay radiatively before any collision. Later on we will introduce collisions between particles (electrons, protons) with excited atoms. The recombination process at low density begins with a radiative recombination, H+ + e− → H0(nl) + γ , which populates an excited state of the hydrogen atom. -
Saturated Absorption Spectroscopy
Ph 76 ADVANCED PHYSICS LABORATORY —ATOMICANDOPTICALPHYSICS— Saturated Absorption Spectroscopy I. BACKGROUND One of the most important scientificapplicationsoflasersisintheareaofprecisionatomicandmolecular spectroscopy. Spectroscopy is used not only to better understand the structure of atoms and molecules, but also to define standards in metrology. For example, the second is defined from atomic clocks using the 9192631770 Hz (exact, by definition) hyperfine transition frequency in atomic cesium, and the meter is (indirectly) defined from the wavelength of lasers locked to atomic reference lines. Furthermore, precision spectroscopy of atomic hydrogen and positronium is currently being pursued as a means of more accurately testing quantum electrodynamics (QED), which so far is in agreement with fundamental measurements to ahighlevelofprecision(theoryandexperimentagreetobetterthanapartin108). An excellent article describing precision spectroscopy of atomic hydrogen, the simplest atom, is attached (Hänsch et al.1979). Although it is a bit old, the article contains many ideas and techniques in precision spectroscopy that continue to be used and refined to this day. Figure 1. The basic saturated absorption spectroscopy set-up. Qualitative Picture of Saturated Absorption Spectroscopy — 2-Level Atoms. Saturated absorp- tion spectroscopy is one simple and frequently-used technique for measuring narrow-line atomic spectral features, limited only by the natural linewidth Γ of the transition (for the rubidium D lines Γ 6 MHz), ≈ from an atomic vapor with large Doppler broadening of ∆νDopp 1 GHz. To see how saturated absorp- ∼ tion spectroscopy works, consider the experimental set-up shown in Figure 1. Two lasers are sent through an atomic vapor cell from opposite directions; one, the “probe” beam, is very weak, while the other, the “pump” beam, is strong. -
Hydrogen Line Project Documentation
Welcome to . The Astronomy Zone! In Which Two D&D Nerds Build a Hydrogen Line Radio Telescope Contents: Moonlighting: Overview 2 Petals to the Metal: Horn Antenna Design Analysis 6 The Crystal Kingdom: SDR, Amplification, and Filtering Setup 11 The Eleventh Hour: Finding the Signal in the Noise with GnuRadio 16 The Stolen Century: Data Collection and Analysis 23 Story and Song: Conclusion 32 Here There Be Gerblins: References 34 Moonlighting: Overview Introduction The exact phrases expressing the excitement that started this project are perhaps not appropriate for general audiences. One of us had successfully used their software defined radio to receive images from orbiting NOAA weather satellites, and was looking for a fun challenge. After wandering through the depths of the radio related internet, the Open Source Radio Telescope website revealed images of a device made of lumber, foam insulation paneling, and fairly standard radio equipment. It was a device designed to investigate the structure and motion of clouds of hydrogen gas across the galaxy, the galaxy. Was it really possible? Another link led to the DSPIRA program, using a very similar telescope as part of an NSF program for teachers. It was real! Just one problem: woefully insufficient background in radio astronomy, spectrometry, digital signal processing, or the necessary software. Who cares though, learning by doing is the best way to learn. No sleep was had that night due to excitement and wondering if this could be pulled off in summer. This was too good and too hard not to be shared though, so a late night inquiry was made to a local space-loving physics major and Dungeon Master extraordinaire, and so here we are. -
1 Hydrogen Line Observations of Cometary Spectra At
Accepted on 01 April 2017; Volume 103 no2, Summer 2017 HYDROGEN LINE OBSERVATIONS OF COMETARY SPECTRA AT 1420 MHZ ANTONIO PARIS THE CENTER FOR PLANETARY SCIENCE ABSTRACT In 2016, the Center for Planetary Science proposed a hypothesis arguing a comet and/or its hydrogen cloud were a strong candidate for the source of the “Wow!” Signal. From 27 November 2016 to 24 February 2017, the Center for Planetary Science conducted 200 observations in the radio spectrum to validate the hypothesis. The investigation discovered that comet 266/P Christensen emitted a radio signal at 1420.25 MHz. All radio emissions detected were within 1° (60 arcminutes) of the known celestial coordinates of the comet as it transited the neighborhood of the “Wow!” Signal. During observations of the comet, a series of experiments determined that known celestial sources at 1420 MHz (i.e., pulsars and/or active galactic nuclei) were not within 15° of comet 266/P Christensen. To dismiss the source of the signal as emission from comet 266/P Christensen, the position of the 10-meter radio telescope was moved 1° (60 arcminutes) away from comet 266/P Christensen. During this experiment, the 1420.25 MHz signal disappeared. When the radio telescope was repositioned back to comet 266/P Christensen, a radio signal at 1420.25 MHz reappeared. Furthermore, to determine if comets other than comet 266/P Christensen emit a radio signal at 1420 MHz, we observed three comets that were selected randomly from the JPL Small Bodies database: P/2013 EW90 (Tenagra), P/2016 J1-A (PANSTARRS), and 237P/LINEAR. -
Light and the Electromagnetic Spectrum
© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © JonesLight & Bartlett and Learning, LLCthe © Jones & Bartlett Learning, LLC NOTElectromagnetic FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION4 Spectrum © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEJ AMESOR DISTRIBUTIONCLERK MAXWELL WAS BORN IN EDINBURGH, SCOTLANDNOT FOR IN 1831. SALE His ORgenius DISTRIBUTION was ap- The Milky Way seen parent early in his life, for at the age of 14 years, he published a paper in the at 10 wavelengths of Proceedings of the Royal Society of Edinburgh. One of his first major achievements the electromagnetic was the explanation for the rings of Saturn, in which he showed that they con- spectrum. Courtesy of Astrophysics Data Facility sist of small particles in orbit around the planet. In the 1860s, Maxwell began at the NASA Goddard a study of electricity© Jones and & magnetismBartlett Learning, and discovered LLC that it should be possible© Jones Space & Bartlett Flight Center. Learning, LLC to produce aNOT wave FORthat combines SALE OR electrical DISTRIBUTION and magnetic effects, a so-calledNOT FOR SALE OR DISTRIBUTION electromagnetic wave. -
(Srt) Recorded 21 Cm Spectral Line of Hydrogen at Vatly Laboratory
VINATOM-AR--12-01 OPERATION OF SMALL RADIO TELESCOPE (SRT) RECORDED 21 CM SPECTRAL LINE OF HYDROGEN AT VATLY LABORATORY Pham Ngoc Donga, Pham Tuan Anha, Pham Ngoc Diepa, Pham Thi Tuyet Nhunga and Nguyen Van Hiepb a Institute for Nuclear Science and Technology, Vietnam Atomic Energy Institute b Institute of Physics, VAST Project information: - Code: 24/CS/HĐ/NV - Managerial Level: Institute - Allocated Fund: 70,000,000 VND - Implementation Time: 12 months (Jan 2012- Dec 2012) - Contact Email: [email protected] , [email protected] - Paper published in related to the project: 1. Nguyen Van Hiep, The VATLY radio telescope, The Second Young Scientist’s Conference on Nuclear Science and Technology, in Hanoi, October 2, 2012. 2. Nguyen Van Hiep et al., The VATLY radio telescope, accepted for publication in Comm. Phys. Vietnam, (2012). ABSTRACT: A small radio telescope (SRT) has been installed on the roof of the Hanoi astrophysics laboratory VATLY. It is equipped with a 2.6 m diameter mobile parabolic dish remotely controlled in elevation and azimuth and with super-heterodyne detection around the 21 cm hydrogen line. They demonstrate the high quality of the telescope performance and are used to evaluate lobe size, signal to noise ratios, anthropogenic interferences and measurement accuracies. Particular attention is given to the measurement of the pointing accuracy. First results of observations of the Sun and of the centre of the Milky Way are presented. I. DESCRIPTION In April 2012, a small radio telescope (SRT) has been installed on the roof of the VATLY astrophysics laboratory [1], commissioned and run-in.