DOCSLIB.ORG

Astronomy Observatories

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Astronomy Observatories National Optical Astronomy Observatories National Optical Astronomy Observatories Quarterly Report April - June 1990 TABLE OF CONTENTS I. INTRODUCTION 1 II. SCIENTIFIC HIGHLIGHTS 2 A. The Latter-day Brightness Variation of the LMC Supernova 1987A 2 B. The Distance to Virgo and the Age of the Universe: New Data from Planetary Nebulae 2 C. Color Gradients in E Galaxies: Measuring the Galaxy Mass? 3 D. High Frequency Solar Oscillations 3 E. Solar-Stellar Observations 4 F. Solar Atmospheric Motions and Structure 6 G. Spectral and High-Resolution Imaging 7 III. PERSONNEL 8 A. Visiting Scientists 8 B. New Hires 8 C. Terminations 8 D. Change of Status 8 E. Summer Research Assistants 9 IV. INSTRUMENTATION, NEW PROJECTS AND OBSERVATORY ACTIVITIES 10 A. Future Telescope Technology Program (FTT) 10 B. Global Oscillation Network Group (GONG) 11 C. WIYN Project 12 D. Instrumentation Projects 12 E. Observatory Activities 15 V. PROGRAM SUPPORT 17 A. Director's Office 17 B. 8-M Office 18 C. Central Administrative Services 18 D. Central Computer Services 19 E. Central Facilities Operations 19 F. Engineering and Technical Services 19 G. Publications and Information Resources 20 Appendices Appendix A: Telescope Usage Statistics Appendix B: Observational Programs I. INTRODUCTION This quarterly report covers scientific highlights for the period of April - June 1990, as well as personnel changes for the period. Highlights emphasize concluded projects rather than work in progress. The report also discusses new technology for telescopes and instrumentation, GONG, WIYN, instrumentation projects, and observatory activities. The Engineering and Technical Services division now submits reports for the instrumentation projects, with contributions from program scientists, if necessary. The Associate Directors for CTIO and NSO continue to provide the information of efforts at La Serena/Cerro Tololo and Sacramento Peak. Activities of the NOAO units are included, and the appendices list telescope usage statistics and observational programs. H. SCIENTIFIC HIGHLIGHTS A. The Latter-day Brightness Variation of the LMC Supernova 1987A. CTIO staff members M. Hamuy and N.B. Suntzeff have analyzed photometric observations covering a 813-day period since the outburst of SN 1987A in the Large Magellanic Cloud (LMC). Because this is the only supernova observed from a reliably known distance, the study of this object is critical in the interpretation of the outbursts of more distant supernovae. The CTIO observations were made in several band-passes ranging from the observable ultraviolet to the near-infrared spectral region. The derived data make possible comparisons of the variations in brightness and color of SN 1987A with those shown by other supemovae of similar type; namely type II-determined by the presence of neutral hydrogen lines in spectra taken soon after outburst. It is now known that while type II supernovae show marked differences in brightness variations in the initial 150 day period after outburst, thereafter all appear to show the same exponential rate of brightness decline up to about 400 days past outburst. This is the period for which reliable apparent brightness information is available for other type II supemovae. While in theory the initial heterogeneity in brightness evolution is caused by differences in the physical nature of the supemovae progenitors, the similar brightness variations between days 150 and 400 after outburst are believed to be controlled by the radioactive decay of 56Co. Of special interest in the Hamuy-Suntzeff study is that when SN 1987A is compared to other more distant type II supemovae, the estimated absolute brightness differences at a given epoch past day 150, and at least up to day 400, are consistent with the uncertainties in the distances of the distant supemovae. Thus the apparent brightness of a given type II supernova after day 150 may be a reliable indicator of its distance. Past day 400 after the outburst, the decline in the optical brightness of SN 1987A was observed to fall off more rapidly. Soon thereafter, observers at the European Southern Observatory (ESO) found that at far infrared wavelengths the supernova had brightened. About the same time, a sudden shift towards the blue was noticed in the supernova's emission spectral lines. In collaboration, N. Suntzeff and ESO astronomer P. Bouchet combined the CTIO and ESO photometric data and noticed that while these changes were occurring, the integrated all-wavelengths radiation from the supernova did not change its decline rate. These various late observations can be interpreted as caused, very likely, by the condensation into dust particles of part of the material ejected by the supernova. B. The Distance to Virgo and the Age of the Universe: New Data from Planetary Nebulae. The most ancient problem in astronomy, that of measuring distances, is still fraught with uncertainty and controversy. Methods used to measure intermediate distances to nearby galaxies are particularly uncertain, since the reliable periodic stars are often too faint, and the redshifts are contaminated by motions induced by local groups and clusters of galaxies. Two years ago an item featured in these scientific highlights described a potentially new and valuable technique for measuring these distances. Developed by J. Jacoby (KPNO), R. Ciardullo (KPNO), H. Ford and J. Neill (ST Scl), the method uses observations of planetary nebulae (PN) in other galaxies. These observers have found that the PN luminosity function has a nearly invariant shape, with a sharp cutoff at a V magnitude of about -4. This upper cutoff allows these objects to be used as standard candles when a large number of them are observed in other galaxies. Jacoby and his collaborators have verified this technique by observations of, and distance determinations to, M31 and the other galaxies in the Local Group. They have now applied this technique to galaxies in the Virgo Cluster, which has one of the most controversial of distance determinations. Past work on this cluster has provided distances which tend to cluster into a "near" value (12 - 16 Mpc) and a "far" value of 20 to 24 Mpc. From a series of observations made at KPNO and at Canada-France-Hawaii Telescope (CFHT), Jacoby et al. have obtained data on the brightness of planetary nebulae in galaxies in the Virgo cluster. These remarkable observations have then allowed an independent determination of the distance to Virgo. The value obtained is 14.7 megaparsecs, which supports the "near" value. One immediate consequence of this is a determination of the age of the Universe. Assuming the motion of the Virgo cluster is pure expansion from the Hubble flow, this measurement gives an age of about 12 billion years, which is very young-younger, in fact, than the age estimates of the oldest stars which lie in the range of 14 to 16 billion years. Resolution of this dilemma may lie in the "Great Attractor." If this giant mass concentration exists, and evidence is growing that it does, then part of the recession velocity of Virgo may be due to the gravitational pull of this object. This effect will reduce the derived value of the Hubble constant and increase the age of the Universe, but the magnitude of this effect is still unclear. In any event, the value of this new method now seems proven, and the distance to the Virgo cluster seems more firmly established at the lower value. C. Color Gradients in E Galaxies: Measuring the Galaxy Mass? The variation of colors within and between elliptical galaxies is a well known phenomenon. These variations are usually interpreted as resulting from changes in the metallicity of the stellar populations in these galaxies. However, the unresolved astrophysical problem is how these metallicity variations come to be. Are they the result of the initial conditions present when the protogalactic gas cloud first condensed? Are they the result of the evolutionary history of the stellar population within the galaxy? What are the effects of the immediate environment of the galaxy now and in the past? Are the observations a result of all of these factors in some combination? Many parameters enter into determining metallicity variations, such as the initial mass function, star-formation efficiency, metal yield from high mass stars, stellar winds, recycling versus galactic winds, and the infall of primordial gas. A new and surprising insight into this phenomenon has come from recent observations made by M. Franx (Ctr. for Astrophys.), G. Ulingworth (Lick Obs.), and T. Heckman (U. of Maryland). Using the KPNO and CTIO 0.9-m telescopes and the ESO 2.2-m telescope, these observers obtained U-R and B-R color profiles in 17 elliptical galaxies. These data were then compared to other properties of the galaxies to search for any correlations that may arise. In general, the colors are more red in higher mass galaxies and change from red to blue with increasing distance from the center of the galaxy. This trend is consistent with metal absorption line strength data in other galaxies and confirms the use of colors as metallicity indicators. The surprising result is that there is a strong correlation between the local color and the local escape velocity in all the galaxies studied, in that the colors become more blue as the escape velocity rises. This strongly suggests that the local escape velocity is the primary factor that determines the metallicity of the stellar population. That such a correlation exists at all is unusual, for many factors could cause a large scatter in such a relation; e.g., mergers, stripping, late gas inflow, velocity anisotropics, etc. The physical mechanism that causes this relation is unclear. It could arise because the star-formation rate is proportional to the energy released in cloud-cloud collisions, or it could be that star-formation proceeds until the energy from supemovae becomes great enough to expel gas locally from the galaxy.
Load more

Recommended publications
  • Constellation Is the Corona Australis
    CORONA AUSTRALIS, THE SOUTHERN CROWN Corona Australis is a constellation in the southern celestial hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax (a shrewmouse; a small, well-furred, rotund animals with short tails). Although fainter than its northern namesake, the oval - or horseshoe-shaped pattern of its brighter stars renders it distinctive. Alpha and Beta Coronae Australis are its two brightest stars with an apparent magnitude of around 4.1. Epsilon Coronae Australis is the brightest example of a W Ursae Majoris variable in the southern sky (an eclipsing contact binary). Lying alongside the Milky Way, Corona Australis contains one of the closest star-forming regions to our Solar System —a dusty dark nebula known as the Corona Australis Molecular Cloud, lying about 430 light years away. Within it are stars at the earliest stages of their lifespan. The variable stars R and TY Coronae Australis light up parts of the nebula, which varies in brightness accordingly. Corona Australis is bordered by Sagittarius to the north, Scorpius to the west, Telescopium to the south, and Ara to the southwest. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'CrA'.
    [Show full text]
  • GEORGE HERBIG and Early Stellar Evolution
    GEORGE HERBIG and Early Stellar Evolution Bo Reipurth Institute for Astronomy Special Publications No. 1 George Herbig in 1960 —————————————————————– GEORGE HERBIG and Early Stellar Evolution —————————————————————– Bo Reipurth Institute for Astronomy University of Hawaii at Manoa 640 North Aohoku Place Hilo, HI 96720 USA . Dedicated to Hannelore Herbig c 2016 by Bo Reipurth Version 1.0 – April 19, 2016 Cover Image: The HH 24 complex in the Lynds 1630 cloud in Orion was discov- ered by Herbig and Kuhi in 1963. This near-infrared HST image shows several collimated Herbig-Haro jets emanating from an embedded multiple system of T Tauri stars. Courtesy Space Telescope Science Institute. This book can be referenced as follows: Reipurth, B. 2016, http://ifa.hawaii.edu/SP1 i FOREWORD I first learned about George Herbig’s work when I was a teenager. I grew up in Denmark in the 1950s, a time when Europe was healing the wounds after the ravages of the Second World War. Already at the age of 7 I had fallen in love with astronomy, but information was very hard to come by in those days, so I scraped together what I could, mainly relying on the local library. At some point I was introduced to the magazine Sky and Telescope, and soon invested my pocket money in a subscription. Every month I would sit at our dining room table with a dictionary and work my way through the latest issue. In one issue I read about Herbig-Haro objects, and I was completely mesmerized that these objects could be signposts of the formation of stars, and I dreamt about some day being able to contribute to this field of study.
    [Show full text]
  • {Download PDF} the New Patterns in the Sky Myths and Legends of The
    THE NEW PATTERNS IN THE SKY MYTHS AND LEGENDS OF THE STARS 1ST EDITION PDF, EPUB, EBOOK Julius D Staal | 9780939923045 | | | | | The New Patterns in the Sky Myths and Legends of the Stars 1st edition PDF Book US presidential election Officials eye blockchain technology for November polls. Lloyd, Lucy 11 October Stars of Pegasus. Another ten have the same stars but different names. Volkswagen ID. Archive for History of Exact Sciences. The star pattern that makes up the Big Dipper is technically part of the aforementioned constellation Ursa Major. I was actually very disappointed with this book. I thought it was going to be a book of myths about the constellations, instead it was a book of weirdness by a single author. Retrieved 9 July Lots of intrigue and family arguments and even some underhanded goings on. To identify the constellations, most observers use star charts , which can be found online and in astronomy books. The illustrations are beautiful. GUR "The Bark". Paris It wasn't there at dusk, but would appear prominently just a few hours later. Pegasus is dominated by a roughly square asterism, although one of the stars, Delta Pegasi or Sirrah, is now officially considered to be Alpha Andromedae , part of Andromeda , and is more usually called "Alpheratz". However, the numerous Sumerian names in these catalogues suggest that they built on older, but otherwise unattested, Sumerian traditions of the Early Bronze Age. They also created stories to go along with these star patterns, which became the basis for many of the myths that have passed through centuries by the Greeks, Romans, Polynesians, Indigenous Americans, and members of various African tribes and Asian cultures.
    [Show full text]
  • Instruction Manual
    iOptron® GEM28 German Equatorial Mount Instruction Manual Product GEM28 and GEM28EC Read the included Quick Setup Guide (QSG) BEFORE taking the mount out of the case! This product is a precision instrument and uses a magnetic gear meshing mechanism. Please read the included QSG before assembling the mount. Please read the entire Instruction Manual before operating the mount. You must hold the mount firmly when disengaging or adjusting the gear switches. Otherwise personal injury and/or equipment damage may occur. Any worm system damage due to improper gear meshing/slippage will not be covered by iOptron’s limited warranty. If you have any questions please contact us at [email protected] WARNING! NEVER USE A TELESCOPE TO LOOK AT THE SUN WITHOUT A PROPER FILTER! Looking at or near the Sun will cause instant and irreversible damage to your eye. Children should always have adult supervision while observing. 2 Table of Content Table of Content ................................................................................................................................................. 3 1. GEM28 Overview .......................................................................................................................................... 5 2. GEM28 Terms ................................................................................................................................................ 6 2.1. Parts List .................................................................................................................................................
    [Show full text]
  • Extrasolar Planets and Their Host Stars
    Kaspar von Braun & Tabetha S. Boyajian Extrasolar Planets and Their Host Stars July 25, 2017 arXiv:1707.07405v1 [astro-ph.EP] 24 Jul 2017 Springer Preface In astronomy or indeed any collaborative environment, it pays to figure out with whom one can work well. From existing projects or simply conversations, research ideas appear, are developed, take shape, sometimes take a detour into some un- expected directions, often need to be refocused, are sometimes divided up and/or distributed among collaborators, and are (hopefully) published. After a number of these cycles repeat, something bigger may be born, all of which one then tries to simultaneously fit into one’s head for what feels like a challenging amount of time. That was certainly the case a long time ago when writing a PhD dissertation. Since then, there have been postdoctoral fellowships and appointments, permanent and adjunct positions, and former, current, and future collaborators. And yet, con- versations spawn research ideas, which take many different turns and may divide up into a multitude of approaches or related or perhaps unrelated subjects. Again, one had better figure out with whom one likes to work. And again, in the process of writing this Brief, one needs create something bigger by focusing the relevant pieces of work into one (hopefully) coherent manuscript. It is an honor, a privi- lege, an amazing experience, and simply a lot of fun to be and have been working with all the people who have had an influence on our work and thereby on this book. To quote the late and great Jim Croce: ”If you dig it, do it.
    [Show full text]
  • Brightest Stars : Discovering the Universe Through the Sky's Most Brilliant Stars / Fred Schaaf
    ffirs.qxd 3/5/08 6:26 AM Page i THE BRIGHTEST STARS DISCOVERING THE UNIVERSE THROUGH THE SKY’S MOST BRILLIANT STARS Fred Schaaf John Wiley & Sons, Inc. flast.qxd 3/5/08 6:28 AM Page vi ffirs.qxd 3/5/08 6:26 AM Page i THE BRIGHTEST STARS DISCOVERING THE UNIVERSE THROUGH THE SKY’S MOST BRILLIANT STARS Fred Schaaf John Wiley & Sons, Inc. ffirs.qxd 3/5/08 6:26 AM Page ii This book is dedicated to my wife, Mamie, who has been the Sirius of my life. This book is printed on acid-free paper. Copyright © 2008 by Fred Schaaf. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada Illustration credits appear on page 272. Design and composition by Navta Associates, Inc. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at www.copy- right.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permissions.
    [Show full text]
  • Constellations
    Your Guide to the CONSTELLATIONS INSTRUCTOR'S HANDBOOK Lowell L. Koontz 2002 ii Preface We Earthlings are far more aware of the surroundings at our feet than we are in the heavens above. The study of observational astronomy and locating someone who has expertise in this field has become a rare find. The ancient civilizations had a keen interest in their skies and used the heavens as a navigational tool and as a form of entertainment associating mythology and stories about the constellations. Constellations were derived from mankind's attempt to bring order to the chaos of stars above them. They also realized the celestial objects of the night sky were beyond the control of mankind and associated the heavens with religion. Observational astronomy and familiarity with the night sky today is limited for the following reasons: • Many people live in cities and metropolitan areas have become so well illuminated that light pollution has become a real problem in observing the night sky. • Typical city lighting prevents one from seeing stars that are of fourth, fifth, sixth magnitude thus only a couple hundred stars will be seen. • Under dark skies this number may be as high as 2,500 stars and many of these dim stars helped form the patterns of the constellations. • Light pollution is accountable for reducing the appeal of the night sky and loss of interest by many young people as the night sky is seldom seen in its full splendor. • People spend less time outside than in the past, particularly at night. • Our culture has developed such a profusion of electronic devices that we find less time to do other endeavors in the great outdoors.
    [Show full text]
  • The COLOUR of CREATION Observing and Astrophotography Targets “At a Glance” Guide
    The COLOUR of CREATION observing and astrophotography targets “at a glance” guide. (Naked eye, binoculars, small and “monster” scopes) Dear fellow amateur astronomer. Please note - this is a work in progress – compiled from several sources - and undoubtedly WILL contain inaccuracies. It would therefor be HIGHLY appreciated if readers would be so kind as to forward ANY corrections and/ or additions (as the document is still obviously incomplete) to: [email protected]. The document will be updated/ revised/ expanded* on a regular basis, replacing the existing document on the ASSA Pretoria website, as well as on the website: coloursofcreation.co.za . This is by no means intended to be a complete nor an exhaustive listing, but rather an “at a glance guide” (2nd column), that will hopefully assist in choosing or eliminating certain objects in a specific constellation for further research, to determine suitability for observation or astrophotography. There is NO copy right - download at will. Warm regards. JohanM. *Edition 1: June 2016 (“Pre-Karoo Star Party version”). “To me, one of the wonders and lures of astronomy is observing a galaxy… realizing you are detecting ancient photons, emitted by billions of stars, reduced to a magnitude below naked eye detection…lying at a distance beyond comprehension...” ASSA 100. (Auke Slotegraaf). Messier objects. Apparent size: degrees, arc minutes, arc seconds. Interesting info. AKA’s. Emphasis, correction. Coordinates, location. Stars, star groups, etc. Variable stars. Double stars. (Only a small number included. “Colourful Ds. descriptions” taken from the book by Sissy Haas). Carbon star. C Asterisma. (Including many “Streicher” objects, taken from Asterism.
    [Show full text]
  • 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 ...............
    [Show full text]
  • First Fringes with ANTU and MELIPAL A
    No. 106 – December 2001 First Fringes with ANTU and MELIPAL A. GLINDEMANN, P. BALLESTER, B. BAUVIR, E. BUGUEÑO, M. CANTZLER, S. CORREIA, F. DELPLANCKE, F. DERIE, P. DUHOUX, E. DI FOLCO, A. GENNAI, B. GILLI, P. GIORDANO, P. GITTON, S. GUISARD, N. HOUSEN, A. HUXLEY, P. KERVELLA, M. KIEKEBUSCH, B. KOEHLER, S. LÉVÊQUE, A. LONGINOTTI, A. LOPEZ, S. MÉNARDI, S. MOREL, F. PARESCE, T. PHAN DUC, A. RAMIREZ, A. RICHICHI, M. SCHÖLLER, J. SPYROMILIO, M. TARENGHI, A. WALLANDER, R. WILHELM, M. WITTKOWSKI 1. Introduction ter control software was installed pro- image quality that was well within speci- viding the additional functionalities that fications: the image size was limited only On October 30, 2001 at about 1 a.m., are required to combine two UTs (see by the seeing of 0.45 arcsec. There was the two 8-m Unit Telescopes ANTU and article on page 2). With the support of no indication that the 200-m light path MELIPAL of Paranal Observatory were NEVEC1, the data pipeline has matured and the 28 reflections between the pri- combined for the first time as a stellar considerably over the last six months, mary 8-m mirror and the CCD affected interferometer observing fringes on the and it now produces results for the vis- the image quality. star Achernar (see Fig. 1), only seven ibility, the transfer months and twelve days after the VLTI function and sta- produced the first fringes with two tistical parameters siderostats. This was the first time that enabling on-line the VLTI was operated as a truly Very data quality con- Large Telescope Interferometer.
    [Show full text]
  • Arxiv:0904.3078V2
    Astronomy and Astrophysics Review manuscript No. (will be inserted by the editor) X-Ray Spectroscopy of Stars Manuel G¨udel Yael¨ Naze´ · Received: 19 February 2009 / Accepted: 3 April 2009 Abstract Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Their X-ray spectra have been important in constraining physical processes that heat plasma in stellar environments to temperatures exceeding one million degree. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense, of X-ray spectra from the solar corona. The Sun itself as a typical exam- ple of a main-sequence cool star has been a pivotal testbed for physical models to be applied to cool stars. X-ray emission from cool stars is indeed ascribed to magnetically trapped hot gas analogous to the solar coronal plasma, although plasma parameters such as temperature, density, and element abundances vary widely. Coronal structure, its thermal stratification and geometric extent can also be interpreted based on various spectral diagnostics. New features have been identified in pre-main sequence stars; some of these may be related to accretion shocks on the stellar surface, fluorescence on circumstellar disks due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot stars clearly dominate the interaction with the galactic interstellar medium: they are the main sources of ionizing radiation, mechan- ical energy and chemical enrichment in galaxies. High-energy emission permits to probe some of the most important processes at work in these stars, and put constraints on their most peculiar feature: the stellar wind.
    [Show full text]
  • 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. arXiv:1412.5182v1 [astro-ph.GA] 16 Dec 2014 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 ...............
    [Show full text]