Table Of ContentASTRONOMY AND
ASTROPHYSICS LIBRARY
Series Editors: I. Appenzeller · G. Bömer · M. Harwit · R. Kippenhahn
P. A. Strittmatter · V. Trimble
Springer-Verlag Berlin Heidelberg GmbH
ASTRONOMY AND
ASTROPHYSfCS IJBRARY
LIBRARY
Series Editors: I. Appenzeller · G. Börner · M. Harwit · R. Kippenhahn
P. A. Strittmatter · V. Trimble
Theory of Orbits (2 volumes)
Volume 1: Integrable Systemsand Non-perturbative Methods
By D. Boccaletti and G. Pucacco
Galaxies and Cosmology
By F. Combes, P. Boisse, A. Mazure and A. Blanchard
The Solar System By T. Encrenaz and J.-P. Bibring
Astrophysical Concepts 2nd Edition By M. Harwit
Physics and Chemistry of Comets Editor: W. F. Huebner
Stellar Structure and Evolution
By R. Kippenhahn and A. Weigert
Modern Astrometry By J. Kovalevsky
Observational Astrophysics By P. Lena
Astrophysics ofNeutron Stars By V M. Lipunov
Supernovae Editor: A. Petschek
General Relativity, Astrophysics, and Cosmology
By A. K. Raychaudhuri, S. Banerji and A. Banerjee
Tools of Radio Astronomy By K. Rohlfs
Atoms in Strong Magnetic Fields
Quantum Mechanical Treatment and Applications
in Astrophysics and Quantum Chaos
By H. Ruder, G. Wunner, H. Herold and F. Geyer
The Stars By E. L. Schatzman and F. Praderie
Physics of the Galaxy and Interstellar Matter
By H. Schefflerand H. Elsässer
GravitationalLenses By P. Schneider, J. Ehlers and E. E. Falco
Relativity in Astrometry, Celestial Mechanics
and Geodesy By M. H. Soffel
The Sun An Introduction By M. Stix
Galactic and Extragalactic Radio Astronomy 2nd Edition
Editors: G. L. Verschuur and K.l. Kellermann
Reflecting Telescope Optics (2 volumes)
ByR. Wilson
F. Combes P. Baisse
A. Mazure A. Blanchard
Galaxies
and Cosmology
Translated by M. Seymour
With 192 Figures
~Springer
Fran~oise Combes Alain Blanchard
DEMIRM - Observatoire de Paris Observatoire de Strasbourg
61 Av. de I'Observatoire 11 Rue de I'Universite
F-75014 Paris, France F-67000 Strasbourg, France
Patrick Boisse
Ecole Normale Superieure Translator:
24 Rue Lhomond
Mark Seymour
F-75231 Paris Cedex 5, France
Department of Logic and Metaphysics
Alain Mazure
University of St Andrews
GRAAL, Universite de Montpellier II St Andrews, Fife KY16 9AL
F-34095 Montpellier Cedex 5, France United Kingdom
Series Editors
Immo Appenzeller Rudolf Kippenhahn
Landesstemwarte, Konigstuhl Rautenbreite 2
D-69117 Heidelberg, Germany D-37077 Gottingen, Germany
Gerhard Borner Peter A. Strittmatter
MPI fiir Physik und Astrophysik Steward Observatory
Institut fiir Astrophysik The University of Arizona
Karl-Schwarzschild-Str.1 Tucson, AZ 85721, USA
D-85748 Garching, Germany Virginia Trimble
Martin Harwit Astronomy Program
The National Air and Space Museum University of Maryland
Smithsonian Institution College Park, MD 20742, USA
7th St. and lndependence Ave. S. W. and Department of Physics
Washington, DC 20560, USA University of California
Irvine, CA 92717, USA
Cover picture: Systems of arclets observed in the galaxy cluster Abell2218 by R. Pe Ilo. The arclets are background
galaxy images deformed by the mass of the cluster acting as a gravitationallens for the light rays. (Photo taken at
Calar Alto 3.5m telescope, CNRS group of Toulouse)
Title of the original French edition: Galaxies et cosmologie
© InterEditions, Paris et Editions du CNRS, Meudon 1991
ISBN 978-3-662-03192-6 ISBN 978-3-662-03190-2 (eBook)
DOI 10.1007/978-3-662-03190-2
Library ofCata1oging-in-Publication Data. Galaxies et cosmologie. English. Ga1axies and cosmology 1 F. Combes
... [el al.]; trans1ated by M. Seymour. p. cm. - (Astronomy and astrophysics 1ibrary) Jncludes bibliographical
references and index. ISBN 3-540-58933-3 (hard: alk. paper) 1. Ga1axies. 2. Cosmology. 3. Astrophysics. 1.
Combes, F. II. Series. QB857.G3913 1995 523.1'1-dc20 95-35265
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©Springer-Verlag Berlin Heidelberg 1995
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Preface
Much progress has been made in our understanding of 'galaxies and cosmology'
since the publication of the French edition of this book in 1991. Four years later it
is interesting to look back on the main advances.
One of the most fundamental issues, the nature of dark matter, has been tackled
in many ways: we now know, from numerous Observations of atomic gas (HI) in
dwarf and giant galaxies, that the relative importance of dark and visible matter
varies along the Rubble sequence. Dwarfs have relatively more dark matter than
giant galaxies. The deftection of light rays by gravitational forces has been widely
used to investigate the total mass and in particular the distribution of dark matter.
Gravitationallensing produces luminous arcs and arclets in clusters of galaxies that
mark out the potential: a very concentrated distribution of dark matter has been
revealed in clusters. Microlensing by stars or compact objects has been observed
and simulated in order to probe the nature of dark matter.
The Hubble Space Telescope has provided an increased spatial resolution that
has allowed the discovery of the long-expected massive black holes at the centres
of elliptical galaxies: a candidate in M87 has now received strong support. As the
telescope operates outside the atmosphere, it can observe in the ultraviolet and has
extended the study of Lyman a absorption lines down to low redshifts. A wealth of
new Lyman a lines has been discovered, establishing that the gas responsible for the
Lyman a forest has not yet disappeared and allowing us to investigate its relation to
galaxies.
The ROSAT X-ray satellite with its enhanced sensitivity has uneavered the struc
ture of galaxy clusters, since the hot X-ray gas isaprobe of the cluster potential.
Contrary to previous belief it now appears that the ratio of dark to luminous matter
does not increase at large distances from the cluster centre.
Finally the COBE satellite has for the firsttime detected ftuctuations in the cosmic
microwave background, which are vestiges of the density ftuctuations that gave birth
to galaxies.
VI Preface
We have attempted to incorporate these new results into our book as far as
possible, or at least to the extent that we estimate they will have a significant impact
on extragalactic research. In spite of this, however, the book is not intended to
be fully comprehensive and complete; its aim is to serve as an introduction at the
graduate Ievel to extragalactic astrophysics and cosmology.
We are very grateful to Mark Seymour for his translation.
Paris, April 1995 Franroise Combes, Patrick Baisse,
Alain Mazure, and Alain Blanchard
From the Preface to the French Edition
The subject of galaxies and cosmology is evolving very rapidly. So, in this book, we
have put the emphasis principally on the methods of investigation, the mechanisms
involved, and the theories capable of providing unified descriptions; at the same
time we have tried our best to review current knowledge and to answer as far as
possible the questions outlined in the General lntroduction. The book covers nearby
galaxies, their dynarnics, and their interactions; quasars and distant radio sources;
and the formation of galaxies and large structures, which then Ieads naturally on to
cosmology and our present view of the early universe.
A Iist of constants, notation, and units used appears at the end of the book.
1t is with pleasure that we thank Suzy Collin, Alain Omont, and Jacques Rolland
for their comments.
Paris, August 1991 Franroise Combes, Patrick Baisse,
Alain Mazure, and Alain Blanchard
Translator's Note
Cosmology, the study of the physical universe on the grandest of scales, is not only
fascinating and inspiring in its own right but is also, I believe, now becoming still
more important and relevant as physics comes full circle, and particle physics and
cosmology literally try to join forces. It was therefore a particular pleasure tobe able
to work on this new book and make it accessible to an English-speaking audience. I
thank Professor Wolf Beiglböck at Springer-Verlag for offering me the opportunity
to do so and for his generosity and understanding throughout. Besides my family,
I should also like to thank Keith Orton and especially Laureut Sauvage for their
help, and of course Professor Fran~oise Combes and her coauthors for their friendly
advice and comments.
St Andrews, May 1995 Mark Seymour
Contents
General Introduction ......................................... .
1 The Classification and Morphology of Galaxies . . . . . . . . . . . . . . . . . 5
1.1 The Classification of Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.1 Hubble's Classification Scheme . . . . . . . . . . . . . . . . . . . . . . 5
1.1.2 De Vaucouleurs's Revised Classification Scheme (1959) . . . 7
1.1.3 Other Elements of the Classification . . . . . . . . . . . . . . . . . . . 9
1.2 Luminosity Distributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2.1 The Luminosity Profile of Ellipticals . . . . . . . . . . . . . . . . . . 11
1.2.2 The Luminosity Profile of Spirals . . . . . . . . . . . . . . . . . . . . . 13
The Central Bulge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
The Disc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
The Vertical Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.3 Stellar Populations, the Distribution of Colour, and Evolutionary
Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.1 Stellar Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.2 The Distribution of Colour . . . . . . . . . . . . . . . . . . . . . . . . . . 20
1.3.3 Evolutionary Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
1.4 The Statistkai Properties of Galaxies . . . . . . . . . . . . . . . . . . . . . . . . 23
1.4.1 The Luminosity Function . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.4.2 Morphological Segregation . . . . . . . . . . . . . . . . . . . . . . . . . . 26
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2 The Galactic Interstellar Medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.1 lonized Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.1.1 Ionized Regions of the Disc . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.1.2 Emission Lines in the Nucleus . . . . . . . . . . . . . . . . . . . . . . . 32
2.1.3 Radio Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
The Nature of the Emission . . . . . . . . . . . . . . . . . . . . . . . . . . 33
General Characteristics of the Emission . . . . . . . . . . . . . . . . 34
2.2 Atomic HI Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.2.1 Excitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.2.2 Global Properties. Correlations . . . . . . . . . . . . . . . . . . . . . . . 40
2.2.3 The Distribution of Atomic Hydrogen . . . . . . . . . . . . . . . . . 41
The Radial Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
X Contents
Interferometric Observations ........................ . 44
The Spiral Structure ............................... . 45
2.2.4 H I Holes and the Connection with Star Formation ....... . 46
2.2.5 Distortion, or Warp, of the Plane ..................... . 49
2.3 The Molecular Phase ................................... . 49
2.3.1 Excitation and the Conversion Ratio .................. . 49
2.3.2 Global Properties. Correlations ...................... . 53
2.3.3 The Radial Distribution ............................ . 53
2.3.4 The Spiral Structure ............................... . 56
2.3.5 The Connection with Activity in the Nucleus ........... . 58
2.3.6 Other Molecules. Abundances ...................... . 61
References 62
3 The Kinematics and Masses of Galaxies ...................... . 63
3.1 Optica1 Determinations .................................. . 63
3.1.1 Metbads ........................................ . 63
3 .1.2 The General Properties of Rotation Curves ............. . 64
3.2 Radio Determinations ................................... . 66
3.2.1 Spiral Arms ..................................... . 68
3.2.2 Bars and Oval Distortions .......................... . 71
3.2.3 Distortion, or Warp, of the Plane ..................... . 73
3.2.4 Asymmetries .................................... . 74
3.3 Determination of the Mass Distribution ..................... . 75
3.3.1 Metbads of Analysis .............................. . 75
Disc Galaxies . . .................................. . 75
Elliptical Galaxies ................................ . 77
3.3.2 The Mass-Luminosity Ratio ........................ . 78
3.3.3 The Tully-Fischer Law and Its Interpretations .......... . 80
Exercises 81
References 82
4 Elliptical Galaxies ......................................... . 83
4.1 Spectroscopic Observations .............................. . 83
4.1.1 General Remarks ................................. . 83
4.1.2 Rotation Velocities 85
4.2 The Three-Dimensional Shape ............................ . 87
4.2.1 Ellipticity Profiles ................................ . 88
4.2.2 Other Tests of the Three-Dimensional Shape ........... . 88
4.3 Models of Elliptical Galaxies ............................. . 93
4.3.1 The Vlasov Equation and Jeans's Theorem ............. . 93
4.3.2 Models of Spherical Galaxies ....................... . 94
f(E) Systems ................................... . 94
f(E, J) Systems ................................. . 96
4.3.3 Models of Axisymmetric Galaxies ................... . 97
