Radio Recombination Lines: Proceedings of a Workshop Held in Ottawa, Ontario, Canada, August 24–25, 1979

280 Pages·1980·11.188 MB·English

by  M. J. Seaton (auth.), P. A. Shaver (eds.)

RADIO RECOMBINATION LINES
ASTROPHYSICS AND
SPACE SCIENCE LIBRARY
A SERIES OF BOOKS ON THE RECENT DEVELOPMENTS
OF SPACE SCIENCE AND OF GENERAL GEOPHYSICS AND ASTROPHYSICS
PUBLISHED IN CONNECTION WITH THE JOURNAL
SPACE SCIENCE REVIEWS
Editorial Board
J. E. BLAMONT. Laboratoire d'Aeronomie, Verrieres, France
R. L. F. BOYD, University College, London, England
L GOLDBERG, Kit! Peak National Observatory, Tucson, Ariz., U.S.A.
C. DE JAGER, University of Utrecht, The Netherlands
Z. KQ:PA{4,\.Uiii~eii'i!'Y dfWant/;lester, England
G. H. LUDWIG, NOAA, National Environmental Satellite Service, Suitland, Md., U.SA.
R. UjST, President Max·Planck·Gesellschaft zur Forderung der Wissenschaften, Miinchen, FR. G.
B. M. McCORMAC, Lockheed Palo Alto Research Laboratory, Palo Alto, Cali/., U.SA.
H. E. NEWELL. Alexandria, Va., U.S.A.
L L SEDOV, Academy of Sciences of the U.S.S.R., Moscow, U.S.S.R.
Z. SVESTKA, University of Utrecht, The Netherlands
VOLUME 80
PROCEEDINGS
RADIO RECOMBINATION
LINES
PROCEEDINGS OF A WORKSHOP
HELD IN OTTAWA, ONTARIO, CANADA, AUGUST 24-25, 1979
Edited by
P. A. SHAVER
European Southern Observatory, Geneva, Switzerland
D. REIDEL PUBLISHING COMPANY
DORDRECHT: HOLLAND I BOSTON: U.S.A.
LONDON : ENGLAND
Library of Congress Cataloging in Publication Data
Radio Recombination Lines.
(Astrophysics and space science library; v. 80)
Includes indexes.
1. Radio recombination lines-Congresses.
l. Shaver, Peter Albert, 1943- II. Series
QB462.5.R32 522'.682 80-1253
ISBN-I3: 978-94-009-9026-5 e-ISBN-I3: 978-94-009-9024-1
001: 10.1007/978-94-009-9024-1
Published by D. Reidel Publishing Company,
P.O. Box 17, 3300 AA Dordrecht, Holland.
Sold and distributed in the U.S.A. and Canada
by Kluwer Boston Inc., Lincoln Building,
160 Old Derby Street, Hingham, MA 02043, U.S.A.
In all other countries, sold and distributed
by Kluwer Academic Publishers Group,
P.O. Box 322, 3300 AH Dordrecht, Holland.
D. Reidel Publishing Company is a member of the Kluwer Group.
All Righ ts Reserved
Copyright © 1980 by D. Reidel Publishing Company, Dordrecht, Holland
Softcover reprint of the hardcover 1s t edition 1980
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical
including photocopying, recording or by any informational storage and
retrieval system, without written permission from the copyright owner
TABLE OF CONTENTS
Foreword VII
List of Participants IX
I - PHYSICS OF RADIO RECOMBINATION LINES
Theory of Recombination Lines M. J. Seaton 3
Laboratory Studies of Rydberg Atoms D. K1eppner 23
II - RADIO RECOt1BINATION LINES FROM HII REGIONS
Interpretation of HII Region Radio C.H. Ttla1ms1ey 37
Recombination Lines
The Importance of non-LTE effects to the R.L. Brown 53
Interpretation of Radio Recombination
Lines
Determination of Electron Temperatures using P.A. Shaver 63
Radio Recombination Lines
Aperture Synthesis Observations of J.H. van Gorkom 67
Recombination Lines from Compact
HII Regions
Radio Recombination Lines from Planetary Y. Terzian 75
Nebulae
Helium Recombination Lines P.G. Mezger 81
Systematic Variation of the Helium N. Panagia 99
Ionization in Galactic HII Regions
Pressure Broadening Effects on the Emission D.A. Cesarsky 107
of He Recombination Lines
III - RADIO RECOMBINATION LINES FROM CII REGIONS
The Partially Ionized Medium Adjacent to V. Pankonin 111
HII Regions
y
vi TABLE OF CONTENTS
Carbon Radio Recombination line Emission from R.L. Brown 127
Dark Clouds
Carbon and Sulphur Ionized Regions ~n Dark E. Falgarone 141
Clouds
Carbon (?) Recombination Lines ~n w49A M.R. Viner and 149
(G43.2-0.0) V.A. Hughes
IV - LARGE SCALE PROPERTIES OF THE GALAXY
The Galactic Center: Results of Radio T. Pauls 159
Recombination Line Surveys
Low Frequency Recombination Lines A. Pedlar and 171
R.D. Davies
Low Frequency Recombination Line Surveys F.J. Lockman 185
of the Galactic Plane
Surveys of Galactic Hydrogen Radio T.L. Wilson 205
Recombination Line Emission
The Evidence for a Gradient of HII Region E. Churchwell 225
Electron Temperatures with Galactic
Radius
On the Electron Temperature of Extended, A. Pedlar and 239
Low Density HII Regions R.D. Davies
V - EXTRAGALACTIC P~DIO RECOMBINATION LINES
Prospects for Observations of Extragalactic P.A. Shaver 247
Radio Recombination Lines
Radio Recombination Lines in Extragalactic M.B. Bell 259
Sources
Closing Remarks J.S. Mathis 269
Name Index 273
Subject Index 277
FOREWORD
Since their first detection 15 years ago, radio recombination lines
from several elements have been observed in a wide variety of objects
including HII regions, planetary nebulae, molecular clouds, the diffuse
interstellar medium, and recently, other galaxies. The observations
span almost the entire range from 0.1 to 100 GHz, and employ both single
djsh and aperture synthesis techniques.
The theory of radio recombination lines has also advanced strongly,
to the point where it is perhaps one of the best-understood in astro
physics. In a parallel development, it has become possible over the last
decade to study these same highly-excited atoms in the laboratory; this
work provides further confirmation of the theoretical framework. However
there has been continuing controversy over the astrophysical interpre
tation of radio recombination line observations, especially regarding
the role of stimulated emission. A workshop was held in Ottawa on 24-25
August, 1979, bringing together many of the active scientists to review
the field and discuss these questions of interpretation.
A broad concensus has emerged: the subtleties of the line-formation
process are understood, and the conditions under which reliable in
formation can easily be extracted from the line measurements are known.
It thus appears likely that the emphasis will shift increasingly from
the study of the line phenomenon itself to further application in other
areas of astrophysics, ranging from physical processes in plasmas
(temperatures, densities, ionization structure), to the large-scale
properties of our galaxy (abundances, kinematics, structure), and studies
of extragalactic systems.
This volume contains the 22 papers presented at the Ottawa workshop.
It is the first book on radio recombination lines, and provides a com
prehensive review of research in this field; it should prove useful both
to active scientists in the field and to graduate students of astrophysics.
I would like especially to thank Dr. L.A. Higgs, my collaborator In
organising this workshop. We are grateful to Drs. J.L. Locke and N.W.
Broten of the Herzberg Institute of Astrophysics for making available
the facilities of the institute, and providing financial support. The
papers were prepared by the authors themselves and submitted in camera
ready form; we thank the D. Reidel Publishing Co. for their cooperation
in producing this volume.
December 1979 P.A. Shaver
Geneva
vii
P.A. Shaver led.), Radio Recombination Lines, vii.
Copyright © 1980 by D. Reidel Publishing Company.
LIST OF PARTICIPANTS
BELL, 11. B. Herzberg Institute of Astrophysics, National
Research Council of Canada, Ottawa, ON K1A OR6,
Canada
BROWN, R.L. National Radio Astronomy Observatory, P.O. Box 2,
Green Bank, WV 24944, USA
CHURCHWELL, E.B. Washburn Observatory, Univ. of Wisconsin,
475 N. Charter St., Madison, WI 53706, USA
DAVIES, R.D. Nuffield Radio Astronomy Laboratories, Jodrell
Bank, Hacclesfield, GB-Cheshire SKU 9DL,
England
DOHERTY, L.H. Herzberg Institute of Astrophysics, National
Research Council of Canada, Ottawa, ON K1A OR6,
Canada
FALGARONE, E. DERAD, Observatoire de Paris, F-92l90 11eudon,
France
GOLDBERG, L. Kitt Peak National Observatory, P.O.Box 26732,
Tucson, AZ 85726, USA
GORKOM, J.H. van Kapteyn Astronomical Institute, Postbus 800,
NL-9700 AV Groningen, The Netherlands
HIGGS, L.A. Herzberg Institute of Astrophysics, National
Research Council of Canada, Ottawa, ON K1A OR6,
Canada
KESTEVEN, M.J. Astronomy Group, Dept. of Physics, Queen's
University, Kingston, ON K7L 3N6, Canada
KLEPPNER, D. Research Laboratory of Electronics, Massachusetts
Institute of Technology, Cambridge, }1A 02139,
USA
LOCK/1A.N, F. J . National Radio Astronomy Observatory, Edgemont Rd.
Charlottesville, VA 22901, USA
ix
P. A. Shaver (ed.). Radio Recombination Lines. ix.
Copyright © 1980 by D. Reidel Publishing Company.
x LIST OF PARTICIPANTS
HACLEOD, J.N. Herzberg Institute of Astrophysics, National
Research Council of Canada, Ottawa, ON KIA OR6,
Canada
HATHIS, J.S. Washburn Observatory, Univ. of Wisconsin,
475 N. Charter St., Madison, WI 53706, USA
MEZGER, P.G. Hax-Planck-Institut f~r Radioastronomie,
Auf dem Hugel 69, D-5300 Bonn 1, West Germany
PANAGIA, N. Laboratorio di Radioastronomia CNR, Via
Irnerio 46, 1-40126 Bologna, Italy
PANKONIN, V. Max-Planck-Institut fur Radioastronomie,
Auf de!'1. Hugel 69, D-5300 Bonn 1, West Germany
PAULS, T.A. Max-Planck-Institut fur Radioastronomie,
Auf dem H~gel 69, D-5300 Bonn 1, West Germany
RADHAKRISHNAN, V. Raman Research Institute, Hebbal P.O.,
Bangalore 560006, India
SCHNID-BURGK, J. Nax-Planck-Institut fur Radioastronomie,
Auf dem Hugel 69, D-5300 Bonn 1, West Germany
SEATON, N.J. Dept. of Physics and Astronomy, University
College London, Gower St., GB-London WCIE 6BT,
England
SHAVER, P.A. European Southern Observatory, c/o CERN,
CH-12ll Geneva 23, Switzerland
TERZIAN, Y. National Astronomy and Ionosphere Center,
Space Sciences Building, Cornell University,
Ithaca, NY 14853, USA
VINER, M.R. Astronomy Group, Dept of Physics, Queen's
University, Kingston, ON K7L 3N6, Canada
WALMSLEY, C.M. Max-Planck-Institut fur Radioastronomie,
Auf dem Hugel 69, D-5300 Bonn 1, West Germany
WILSON, T.L. Max-Planck-Institut f~r Radioastronomie,
Auf dem Hugel 69, D-5300 Bonn 1, West Germany
PART I
PHYSICS OF RADIO RECOMBINATION LINES
"The uncertainty is in the astronomy,
not in the physics"
- M.J. Seaton