High Angular Resolution in Astrophysics

403 Pages·1997·15.27 MB·English

by  Pierre Lena (auth.)

High Angular Resolution in Astrophysics
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Series C: Mathematical and Physical Sciences - Vol. 501
High Angular Resolution
in Astrophysics
edited by
Anne-Marie Lagrange
Charge de Recherche au CNRS,
Laboratoire d'Astrophysique de Grenoble,
Grenoble, France
Denis Mourard
Astronome-Adjoint,
Observatoire de la Cote d'Azur,
Departement Fresnel,
Nice, France
and
Pierre Lena
Universite Paris VII
& Observatoire de Paris,
Paris, France
Kluwer Academic Publishers
Dordrecht / Boston / London
Published in cooperation with NATO Scientific Affairs Division
Proceedings of the NATO Advanced Study Instiute on
High Angular Resolution in Astrophysics
Les Houches, France
9-19 April 1996
A C'!.P. Catalogue record for this book is available from the Library of Congress
ISBN-13: 978-94-0 I 0-6507-8
Published by Kluwer Academic Publishers,
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Printed on acid-free paper
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ISBN-13: 978-94-010-6507-8 e-ISBN-13: 978-94-009-0041-7
DOl: 10.1007/978-94-009-0041-7
© 1997 Kluwer Academic Publishers
Softcover reprint of the hardcover 1st edition 1997
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TABLE OF CONTENTS
Preface .................................................. ix
Group photo ............................ ......... . . . . . .. xiii
List of participants .................................... ..... xv
mGH ANGULAR RESOLUTION INSTRUMENTATION .......... 1
An introduction to atmospheric turbulence
by P. Lena ............................................. 3
Design of arrays for ground based optical interferometry
by S.T. Ridgway ......................................... 13
Kilometric baseline interferometry
by P.Y. Bely ............................................ 39
Observing with optical/infrared long baseline interferometers
by J. Davis ............................................. 49
Imaging in interferometry
by O. Von der Liihe and N. Ageorges ......................... 81
Astrometry with OIIR interferometers
by M. Shao ............................................ 109
Image reconstruction: from basic notions towards methodological
strategies
by A. Lannes ........................................... 115
vi
Radio interferometry
by S. Guilloteau ........................................ 145
Very long baseline interferometry
by W.D. Cotton ......................................... 165
Laser guide star
by R. Foy ............................................. 193
ASTROPHYSICS AND mGB ANGULAR RESOLUTION . ........ 231
Solar-system studies at high angular resolution
by T. Encrenaz ......................................... 233
Circumstellar material around main sequence and evolved stars
by F. Paresce .......................................... 259
Life on extra-solar planets
by A. Leger ............................................ 285
High angular resolution studies of starburst galaxies
by D. Rouan ........................................... 293
ORAL CONTRmUTIONS .................................. 317
A new detector for wavefront sensing in adaptive optics applications
by A.W. Kluttig and J.L.A. Fordham ......................... 319
Factors affecting the performance of stellar interferometers: application to
the VL TI error budgets
by B. Koehler .......................................... 325
Optical interferometry and ground-based astrometry after the
Hipparcos mission
by G. Daigne ........................................... 337
VII
Improving the natural guide star magnitude limit for wavefront sensing
in an open loop system
by o. Esslinger and M.G. Edmunds ......................... 343
Dispersion compensation and fringe tracking
P.R. Lawson ........................................... 349
Local piston detection of a segmented mirror telescope with curvature
sensing of wavefronts affected by atmospheric turbulence. Numerical
simulations
by J.M. Rodriguez-Ramos and J.J. Fuensalida ............... 355
The first Caltech-Jodrell bank VLBI survey: a morphological
classification scheme of powerful radio sources
by AG. Polatidis ........................................ 359
Adaptive optics imaging of the pre-main sequence star YY Orionis
by F. Menard and F. Malbet ............................... 365
Detecting disks around young stellar objects with infrared
interferometers
by F. Malbet ........................................... 371
Detection of circum stellar dust shell around supergiant TV Gem from
milliarcsecond resolution near infrared observations
by S. Ragland, T. Chandrasekhar and N.M. Ashok .............. 379
Combined HST and HAR imaging and photometry of eruptive binaries
in globular cluster cores: based upon observations taken with the
William Herschel Telescope on La Palma and the Hubble Space
Telescope
by R. Butler, A Shearer and M. Redfern ...................... 383
An indirect search for low-mass companions to distant stars
by M.V. Sazhin and I.A Trifalenkov ......................... 391
Subject index •.•.........................•.............. 397
PREFACE
Since 1970, when Antoine Labeyrie first broke the seeing barrier and
reached the diffraction-limited resolution of large telescopes observing from
ground-based sites in the visible, the emergence of high angular resolution
at optical (visible and infrared) has been progressive and is nowadays be
coming spectacular. Speckle methods, first in the visible and soon in the
infrared brought the first astrophysical results, mostly on double stars and
circumstellar environments, using painful reconstruction methods to ob
tain an important but limited amount of information. But their systematic
developement led to an unprecedented and detailed knowledge of the at
mospheric turbulence and of its effects on astronomical images, including a
better understanding of the parameters to be taken in account when a new
astronomical site is selected, or when a large telescope is built . This was
capital for the steps to follow.
The next step blossoms since the end of the eighties, with the remark
able development of adaptive optics, which capitalizes on the knowledge
accumulated on the Earth's atmosphere and becomes to-day a mandatory
su b-system in the conception of large or even moderate size telescopes. Sci
entific productivity of adaptive optics, in the near-infrared and now in the
visible, is already demonstrated in almost every field of astrophysics, with
imaging, spectro-imaging or polaro-imaging of planetary surfaces, solar sys
tem objects, multiple stars and star clusters, circumstellar environments,
nuclei of galaxies and quasars. Comparison of such results with images ob
tained with the Hubble Space Telescope demonstrates the effective quality
and great future of what is obtained from the ground. The next step for
adaptive optics is to get rid of the intrinsic limitations in the magnitude of
the objects it can actually correct. Artificial laser star programs, promising
but expensive, may bring the ultimate solution within a few years.
Although multi-telescope interferometry has been first achieved in 1974,
again by Antoine Labeyrie, progress in astrophysical uses of it has been
much slower. The years 1980s have seen a number of prototype instruments
implemented, which brought significant but limited results. This fact is a
IX
x
natural result of the increased complexity and the experimental challenges
which have to be faced when one couples meter- size telescopes, tens or
hundreds of meters apart, while keeping an optical path accuracy of a few
tens of nanometers between the various light beams. But there is a funda
mental point which has been achieved during these years of exploration:
the physics of beam recombination at optical wavelengths, as well as the
atmospheric effects on the phase of the incoming wave, are perfectly un
derstood, as was demonstrated, among other results, by some remarkable
achievements in astrometryobtained at Mt. Wilson by Michael Shao and
coworkers. Therefore, difficulties are only of a technical nature, and can be
solved when appropriate resources are allocated.
Facing this and perceiving the wealth of astronomical results -almost a
revolution- which can result from a resolution gain of factors 10-30 com
pared to single telescope operation, the astronomical community embarked,
at the end of the eighties, in the construction of powerful optical interfer
ometers, remarkable either by the size of the telescopes to be combined
-the giants one in the lO-m class currently under construction-, or by their
number, or by various combinations of these two factors. If the European
Very Large Telescope or the Keck-Telescopes represent the most impressive
ambition in this respect, a number of other arrays demonstrate the confi
dence currently placed by astronomers in this new tool of astronomy, which
will become available to them in the very first years of the next millenium.
In addition, after years of uncertainties and adventurous concepts, optical
interferometry in space appeared also to become a reality : an interfero
metric space mission is programmed in the United States, and at least one
is seriously envisaged in the European space program.
It therefore appeared timely to hold at Les Houches a school on High
Angular Resolution in Astrophysics, in order to prepare the exploitation of
these powerful interferometers. It was then decided by the Scientific Orga
nizing Committee to concentrate on multi-telescope interferometry at opti
cal wavelengths: the justification of this choice immediatly results from the
above described status of the field. The title of the school may be mislead
ing, as it seems to cover the whole wavelengths range. Although it appeared
more appropriate to restrict the topics to the optical, it was indeed recog
nized that many lessons remain to be learned from the long-lasting and
elaborate practice of interferometry achieved at radio-wavelengths, which
is therefore present in the lectures. The initial intent was to focus on sci
ence programs and they indeed represent a significant part of the present
Volume. They would have been even more present if some of the authors
had not finally declined to provide their manuscript, undoubtly overloaded
by writing obligations of various kinds. This is regrettable, but a sufficient
number of papers covering a great variety of astrophysical topics, written
xi
by authoritative scientists, is present for the main goal of the school to be
properly represented here.
The lectures which present the existing or planned interferometers out
line the performances an astronomer, not necessarily specialist in interfer
ometry, can expect when he considers to use such a system for a definite
goal of his own. They should help to bridge the gap between the quite
special and yet esoteric language of distinguished interferometrists and the
rest of the astronomical community.
The eagerness and youth of the attendance were certainly perceived by
all, and give confidence in the creativity of the generation which will exploit
the extraordinary instruments currently in construction. Les Houches in
spring time carry their own special flavor, so different from the summer or
the fall in this heart of the French Alps. So many great scientific ventures
took off from this exceptional place that we all felt to be in good company!
It is a pleasure to thank here the colleagues who contributed by their
lectures and active presence, the ones who gave short contributions, the
students for their cheerful spirit during the school.
We are grateful to the NATO Scientific Affairs Division who generously
supported this ASI. We also thank our Kluwer contact, Mrs W. Bruins
for her help. We also thank all the institutions which participated to the
funding of the school : the Ecole de Physique des Houches, the Centre
National de la Recherche Scientifique, the European Space Agency and the
Centre National d'Etudes Spatiales, and the french Programme National
pour la Haute Resolution Angulaire en Astrophysique. The staff of the
Laboratoire d'Astrophysique de I'Observatoire de Grenoble and that of the
Ecole de Physique des Houches assisted us very efficiently. We thank them
for their help.
We hope that students and researchers interested in High Angular Res
olution in Astrophysics will find this book useful and stimulating.
Anne-Marie Lagrange
Denis Mourard
Pierre Lena