NEW EXTRAGALACTIC PERSPECTIVES IN THE NEW sourn AFRICA

ASTROPHYSICS AND SPACE SCIENCE LIBRARY

VOLUME 209

Executive Committee

W. B. BURTON, Sterrewacht, Leiden, The Netherlands J. M. E. KUIJPERS, Faculty 0/ Science, Nijmegen, The Netherlands

E. P. J. VAN DEN HEUVEL, Astronomical Institute, University 0/ Amsterdam, The Netherlands

H. VAN DER LAAN, Astronomical Institute, University 0/ Utrecht, The Netherlands

Editorial Board

1. APPENZELLER, Landessternwarte Heidelberg-Konigstuhl, Germany J. N. BAHCALL, The Institute/or Advanced Study, Princeton, U.S.A.

F. BERTOLA, Universita di Padova, Italy W. B. BURTON, Sterrewacht, Leiden, The Netherlands

J. P. CASSINELLI, University o/Wisconsin, Madison, U.S.A. C. J. CESARSKY, Centre d' Etudes de Saclay, Gi/-sur-Yvette Cedex, France

J. M. E. KUIJPERS, Faculty 0/ Science, Nijmegen, The Netherlands R. McCRAY, University o/Colorado, JILA, Boulder, U.S.A.

P. G. MURDIN, Royal Greenwich Observatory, Cambridge, U.K. F. PACINI, Istituto Astronomia Arcetri, Firenze, Italy

V. RADHAKRISHNAN, Raman Research Institute, Bangalore, India F. H. SHU, University o/Cali/ornia, Berkeley, U.S.A.

B. V. SOMOV, Astronomical Institute, Moscow State University, Russia R. A. SUNYAEV, Space Research Institute, Moscow, Russia

S. TREMAINE, CITA, University o/Toronto, Canada Y. TANAKA, Institute 0/ Space & Astronautical Science, Kanagawa, Japan

E. P. J. VAN DEN HEUVEL, Astronomical Institute, University 0/ Amsterdam, The Netherlands

H. VAN DER LAAN, Astronomical Institute, University o/Utrecht, The Netherlands

N. O. WEISS, University o/Cambridge, U.K.

NEW EXTRAGALACTIC PERSPECTIVES IN

THE NEW SOUTH AFRICA Proceedings of the International Conference on

"Cold Dust and Galaxy Morphology" held in Johannesburg, South Africa,

January 22-26, 1996

Edited by

DA VID L. BLOCK Department o/Computational and Applied Mathematics,

University o/the Witwatersrand, Johannesburg, South Africa

and

J. MAYO GREENBERG Huygens Astrophysics Laboratory,

University o/Leiden, The Netherlands

KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON

A C.I.P. Catalogue record for this book is available from the Library of Congress

ISBN-l3: 978-94-010-6637-2 e-ISBN-13: 978-94-009-0335-7 DOl: 10.1007/978-94-009-0335-7

Published by Kluwer Academic Publishers, P.O. Box 17, 3300 AA Dordrecht, The Netherlands.

Kluwer Academic Publishers incorporates the publishing programmes of

D. Reidel, Martinus Nijhoff, Dr W. Junk and MfP Press.

Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers,

101 Philip Drive, Norwell, MA 02061, U.S.A.

In all other countries, sold and distributed by Kluwer Academic Publishers Group,

P.O. Box 322, 3300 AH Dordrecht, The Netherlands.

Printed on acid-free paper

All Rights Reserved © 1996 Kluwer Academic Publishers

Softcover reprint of the hardcover 1st edition 1996

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 information storage and retrieval system, without written permission from the copyright owner.

NEW EXTRAGALACTIC PERSPECTIVES IN THE NEW SOUTH

AFRICA

Changing Perceptions of the Morphology, Dust Content and Dust-Gas Ratios in Galaxies: January 22 - 26 1996

Scientific Organizing Committee:

R.J. Allen (USA) G. Bertin (Italy) D.L. Block (South Africa; SOC Chairperson) B.W. Burton (Netherlands) N. Devereux (USA) J.M. Greenberg (Netherlands) P. Grosb¢l (Germany) R.D. Joseph (USA) J. Lequeux (France) A.N. Witt (USA)

Local Organizing Committee at the Witwatersrand University: Professors J.P.F. Sellschop (Deputy Vice-Chancellor: Research), P.D. Tyson (Chairman of the National Astronomy Facilities Board: South Africa), R. Crewe (Dean: Science Faculty), C.J. Wright (Head: CAMS) and D.L. Block (CAMS; Chairman of the LOC); G.C. Buric (CAMS), E. Momo­niat (CAMS) and M. Nakayama (CAMS). Other LOC Members: Dr R.S. Stobie (Director: SAAO), Dr L. Alberts (former Chairman, South African Academy of Science and Arts); E.K. Block (Vista University), P. van Huyssteen (Price, Waterhouse and Meyernel), T. Hanson (Rennies Conference Man­agement), S. Irish (Sunnyside Residence) and M. Doidge (Wits). Secretariat: Mrs Florence Goetze. SOC Secretariat: E. Momoniat

Registration Desk & Camera Ready Copy: De Wet Ferreira, Siona Bradu, Meg Doidge, Ebrahim Momoniat.

COVER CAPTIONS

Front Cover - (top): Images secured through H, Rand B filters ofthe famous interacting 'Antennae'

galaxy pair NGC 4038/9 (= Arp 244 = VV 245) were assigned to the red, green and blue guns respectively, of a colour digital camera. The difference in the stellar content of the two galaxies is very striking. Approximately 40% of HI in the system is associated with the two galaxies seen here; the remaining 60% is associated with the luminous tails. The observers were K. Sellgren and G. Tiede, using the 1.5m at Cerro Tololo Inter-American Observatory in Chile. Courtesy J. Frogel.

Front Cover - (bottom): The spiral galaxy NGC 2997. Left: Optical photographs of NGC 2997 (courtesy

D. Malin and the Anglo-Australian Observatory) and B CCD images (courtesy S. d'Odorico with the ESO NTT) reveals an optically grand design, m=2 morphology. Middle: A near-infrared 2x3 mosaic at 2.1 microns with the ESO 2.2m telescope, reveals a distinct m=1 stellar component. Observers at ESO, La Silla: D. Block and A. Moneti. Right: After reb inning to a common scale of the Band K' images, widespread inter arm dust (colour coded so that dust=black) is seen at arcsecond resolution in this B-K' map, produced by D. Block and P. Grosb¢l. Reproduced courtesy Astronomy and Astrophysics.

Back Cover: A three dimensional projection of a near-infrared image of the optically floc­

culent spiral galaxy NGC 2841 reveals a remarkable system of long, dark infrared spiral arms. The very regular and smooth dark, gaseous spiral arms appear as 'valleys' in this relief projection, and have no stellar counterparts. The arms each span an azimuth of 1600 • Image produced using the IBM Data Explorer by B.G. Elmegreen and C. Pickover, from 2.1 micron NICMOS images secured at Mauna Kea, Hawaii by R.J. Wainscoat. Courtesy Nature.

CONTENTS

Invited review papers are identified by a t after the surname of the review speaker. A * in a title implies that colour platers) from the author(s) are located in the separate Colour Plate Section

THE SOC AND LOC V

THE EDITORS - Preface xv

OFFICE OF THE PRESIDENT - Message from President N.R. Mandela xxiii

D.L. BLOCK t - Changing perceptions of the morphology and dust content in galaxies * 1

M. DISNEY - How cold could galaxies be? 21

W. W. DULEY - Temperature fluctuations and very cold dust 29

J.C. MATHERt - The interstellar medium as observed by COBE 34

R.J. ALLEN - Molecular gas in spiral galaxies 50

O.C. DE JAGER - Cold dust signatures on SNR gamma ray spectra 61

J.A. FROGEd, A.C. QUILLEN AND R.W. POGGE - Optical and infrared images of galaxies: What's to be learned?* 65

R.B. TULLyt AND M.A.W. VERHEIJEN - Optical, IR and HI observations of a large complete cluster sample 84

M.W. REGAN - The relationship between near IR extinction and CO emission 98

C. Xu AND V. BUAT - Extinction and dust column density in spiral disks from FIR vs UV-Optical comparison 105

D.L. DEPOY, A.C. QUILLEN, A. BERLIND AND S.V. RAMIREZ - The effects of supergiants on the infrared light distribution in galaxies 109

R.E. WHITE III - Reflections at the Registration Desk 113

R.E. WHITE III, W.C. KEEL AND C.J. CONSELICE - Distribution and Con-tent of dust in overlapping galaxy systems 114

J. MAYO GREENBERGt AND A. LI - Evolution and emission of cold, warm and hot dust populations in diffuse and molecular clouds 118

Y.J. PENDLETON - Organics and ices in galactic dust 135

viii CONTENTS

G.S. WRIGHT, A. BRIDGER, T.R. GEBALLE AND Y. PENDLETON - Studies of NIR dust absorption features in the nuclei of Active and IRAS galaxies 143

K. SELLGREN - Tiny grains and large molecules in the Milky Way and other galaxies 151

N. BROSCH AND B. BILENKO - The role of UV observations in understanding dust and its morphology 155

G.R. CARRUTHERS - Studies of interstellar dust and gas with the far ultra-violet cameras and far ultraviolet imaging spectrograph space shuttle in-vestigations 159

B.J. SMITH - High spatial resolution 50 and 100 micron KAO observations of infrared-bright galaxies 170

L.E. KUCHINSKI AND D.M. TERNDRUP - Infrared photometry and dust ab-sorption in highly inclined spiral galaxies 178

G.C. CLAYTON - The nature of interstellar dust in Local Group galaxies from observations of extinction and polarization 183

P. BOISSE AND S. THORAVAL - Structure in the distribution of the dust and its impact on extragalactic studies 187

N.D. KYLAFIS AND E.M. XILOURIS - Determination ofthe 3D dust distribu-tion in spiral galaxies 195

E. EMSELLEM - A 3D dust model for the Sombrero galaxy 203

1.S. GLASS - Doubling of the infrared flux from NGC1068: a circumnuclear dust torus? 207

R.E. GRIFFITHst, K.U. RATNATUNGA, S. CASERTANO, M. 1M, N. ROCHE, L.W. NEUSCHAEFER, R.S. ELLIs, G.F. GILMORE, R.A.W. ELSON, A. ABRAHAM, K GLAZEBROOK, B. SANTIAGO, R.F. GREEN, V. SARA­JEDINI AND J.P. HUCHRA - Resolving the faint galaxy excess with HST: Results from the Medium Deep Survey 211

G. BERTIN t - Spiral structure in galaxies: Competition and cooperation of gas and stars 227

R.A. GONZALEZ, G. BRUZUAL A., G. MAGRIS C. AND J.R. GRAHAM -Color gradients in M99: Stellar populations or dust? 243

P. GROSB0L AND P .A. PATSIS - Amplitude and shape of spiral arms in J('

(*) 251

S. COURTEAU t - The bulge/disk connection in late-type spirals 255

D. CALZETTI - Dust in starburst galaxies: From the ultraviolet to the near infrared 271

D.M. ELMEGREEN - Near-infrared surface photometry of barred spiral galax-~ 2~

E. ATHANASSOULA - Barred galaxies in the near-IR: Observations and dy-namical implications 28~

CONTENTS ix

A. BOSMA - Morphology and dynamics of a few giant galaxies with low surface brightness disks 287

D. PFENNIGER, L MARTINET AND F. COMBES - Secular evolution of galaxy morphologies 291

T.Y. STEIMAN-CAMERON - Dusty disks and the structure of early-type galax-Ies 301

P. HODGEt - Dust and gas in Local Group galaxies 309

R.M. RICH, K.J. MIGHELL, J.D. NEILL AND W.L. FREEDMAN - The nuclear regions of M31, M32 and M33 imaged by the Hubble Space Telescope* 325

R. CHINIt AND E. KRUGEL - Gas and dust in normal and active galaxies 329

P. ANDREANI AND A. FRANCESCHINI - mm observations of IRAS galaxies: Dust properties, luminosity functions and contributions to the sub-mm background 345

N. NEININGER AND M. GUELIN - Mapping the cold dust in edge-on galaxies at 1.2mm wavelength* 349

B. CUNOW AND W.F. WARGAU - Internal absorption in spiral galaxies using four colours 353

N. DEVEREuxt - Dust in galaxies: A far infrared perspective 357

E.J. DE GEUS t - Search for cold molecular gas 373

F. GARZON, P.L. HAMMERSLEY, X. CALBET, T.J. MAHONEY AND M. LOPEZ-CORREDOIRA - Galactic structure and morphology of the Milky Way from the TMGS 388

A.P. FAIRALL, P.A. WOUDT AND R.C. KRAAN-KORTEWEG - Unveiling large-scale structures behind the Milky Way 396

P. GOUDFROOIJ - The distribution of dust and gas in elliptical galaxies* 400

F. MACCHETTO, N. CAON, W.B. SPARKS AND M. PASTORIZA - The ionized gas in early-type galaxies 408

D.A. FORBES - HST imaging of the dust in kinematically distinct core ellip-ticals 416

J. LEQUEUxt AND M. GUELIN - Dust and gas in the outer parts of galaxies 422

J. SCHAEFER - Dust spectra ofthe Milky Way: Primordial molecular hydrogen and helium in the outer Galaxy 435

D. PFENNIGER - Fundamental aspects of the ISM fractality* 439

C. CARIGNAN - The DM-HI connection 447

F. COMBEst AND D. PFENNIGER - Very cold gas and dark matter 451

B.G. ELMEGREEN - Constraints on the surface density of gas in outer galaxy disks from stability analyses 467

J .A. GRAHAM - The changing circumstellar environment of young stars 480

D.P. CRUIKSHANK - Interstellar dust in the solar system 485

x CONTENTS

D. WARD-THOMPSON AND N.E. JESSOP - Pre-stellar cores and the initial conditions for star formation 489

A. CIMATTI - Dust and Morphology of high redshift radio galaxies: Clues from scattering 493

P.J. FRANCIS, R.J. WEBSTER, B.A. PETERSON, M.J. DRINKWATER AND F.J. MASCI -Dust obscured Quasars 501

C.D. IMPEY - The opacity of low surface brightness galaxies and their contri-bution to Quasar absorption* 505

P.M. KNEZEK - The morphology of massive, gas-rich low surface brightness galaxies 509

G.J. STACEY, T.L. HAYWARD, G.E. GULL AND H. LATVAKOSKI - 38 micron images of galaxies: The infrared luminosity 513

Poster Papers

N. BROSCH - Dust in early-type galaxies: New results on the wavelength de-pendence of the extinction 521

R.L.M. CORRADI, J.E. BECKMAN, M.S. DEL RIO, A. DI BARTOLOMEO AND E. SIMONNEAU - New radiative transfer models of disc galaxies and the scale-length test for dust diagnostics 523

J.1. DAVIES, M. TREWHELLA AND H. JONES - The distribution of cold dust within the Galaxy 525

P.J. FRANCIS AND B.E. WOODGATE - Detection of extended dust in a radio-quiet galaxy at redshift 2.38 52E

T.J. MAHONEY, P.L. HAMMERSLEY, M. LOPEZ-CORREDOIRA, F. GARZON AND X. CALBET - Extinction in the direction of the end-of-bar star for-mation region 53(

X. CALBET, M. LOPEZ-CORREDOIRA, P.L. HAMMERSLEY, T. MAHONEY, F. GARZON AND J.E. BECKMAN - Sampling the bar population 53~

P.L. HAMMERSLEY, T. MAHONEY, F. GARZON, X. CALBET AND M. LOPEZ-CORREDOIRA - Chasing shadows in the TMGS 53,

1.S. GLASS - Imaging the inner Galaxy* 531

M.A. GREENHOUSE, S. SATYAPAL, H.A. SMITH, C.E. WOODWARD, J. FIS-CHER, W.J. FORREST, J. PIPHER AND D.M. WATSON - Fabry-Perot imaging of dust grain processing in M82 53'

W.K. HUCHTMEIER - The HI content of a complete sample of Sa galaxies 54

N.H. IBRAGIMOV - Massive galactic halos and dark matter: Unusual proper-ties of neutrinos in the de Sitter Universe 54

R.J. IVISON AND E.N. ARCHIBALD - Dust in a radio galaxy at z=4.25 54

J. MURTHY, D.T. HALL, R.C. HENRY AND J.B. HOLBERG - Voyager obser-vations of dust scattered starlight 54

CONTENTS xi

N. PANAGIA, A CAPETTI, S. SCUDERI, H. LAMERS AND R.P. KIRSHNER-Dust and stars in the nuclear region of M51 * 552

P.A. PATSIS AND P. GROSB0L - Gaseous and stellar responses to spiral per-turbations detected in the NIR 554

R.B. ROUSE - Attenuation and stellar population gradients in spiral galaxies 556

S. SAUTY, M. GERIN AND F. CASOLI - FIR and cn emissions in NGC6946 559

U.J. SOFIA - The composition of interstellar dust 561

W.B. SPARKS, S. DE KOFF, S. BAUM, D. GOLOMBEK, F MACCHETTO, J. BIRETTA, G. MILEY AND .P. MCCARTHY - Dust in radio galaxies: Clues to activity 564

M.D. THORNLEY - Defining spiral structure in the flocculent galaxy NGC5055 566

M. TREWHELLA, J.L DAVIES AND M.J. DISNEY - Where does dust absorb most light? 568

S. VON LINDEN, H. LESCH AND F. COMBES - On the angular-momentum transport in spiral and barred galaxies 570

R.D. WOLSTENCROFT AND R.D. DAVIES - Dust, stars and nuclear activity in the centres of Sbc galaxies 573

S.M. SCARROTT AND R.D. WOLSTENCROFT - The polarizing properties of dust in NGC5128 576

Concluding Thoughts

G.C. BURIC - Astronomy at the University of the Witwatersrand 578

R.J. ALLEN, B. G. ELMEGREEN, P. HODGE AND J. C. MATHER - Eyes to the Future: An Interactive Panel/Audience Discussion 585

The CHAIRPERSONS - Each Chairperson Reflects on their Session 612

B.G. ELMEGREEN - The Riddle... 626

D.1. BLOCK - 'Where dust is stars' 627

THE PARTICIPANTS 629

THE COLOUR PLATES 635

THE PREFACE

The date: September 30, 1880 The place: A private observatory in Hastings-on-Hudson Profession of the observer: A medical doctor The instrument: An l1-inch Clark refractor.

The significance of that night marked one of the truly great turning points in the development of astronomical techniques: Dr Henry Draper, a wealthy New York medical doctor, had secured the first photograph of a nebula: a 51-minute exposure on a dry gelatinobromide plate showing the wispy nebulosity of the Orion Nebula. By March 1882, Draper had secured an exposure of 137 minutes, showing far richer detail of both bright and dark features.

The rest is histapy. The photographic era heralded in a universe where hints of the presence of cosmic dust were strongly alluded to: from star-forming regions such as Messier 17, to the Horsehead Nebula in Orion, to the striking dark finger in the Cone Nebula, to the magnificent dark bands in the plane of our Milky Way.

"Historically, astromomers from the very beginning have been afraid of dust. But since it had to be accepted, it was hoped that its properties were universal and constant so that corrections for stellar distances could be simply made. But life is not so simple, and passive 'teflon' dust was an impossible dream. For example, molecular clouds: all the chemical work that was done on molecules in clouds was done using only gas phase interactions such as ion molecule reactions, absolutely ignoring the fact that each cold dust grain is a remarkable chemical factory. As­tronomers ignored, or tried to ignore the effects of dust from so many points of view that it is impossible for me to sum them all up here." (JMG)

Professor Michael Disney summed it up eloquently: "For most astronomers dust is quite simply a nuisance. They want to be con­

firmed in their fervent hope that there isn't much of it about and they would be happy to see the heretics burned."

What is the nature and composition of the dust grains responsible for the visual extinction in our Galaxy and in other galaxies beyond? What are the ranges in temperature of dust grains? Can these be less than 2.7K, the temperature of the cosmic blackbody background? Can cold dust grains be studied optically at unprecedented arcsecond resolution? Might such grains account for dust mass increases by up to one order of magnitude? How does the presence of dust affect the morphology of a galaxy? In particular, can the near-infrared classification of a galaxy be radically different from its optical Hubble type, once the dust veil is lifted? Is this new dust-penetrated view bringing us to the verge of a breakthrough in understanding the connection between galaxy morphology and the underlying

xv

xvi PREFACE

physics of galaxies? Are there significant amounts of cold molecular hydrogen gas in galactic disks?

Michael Disney quipped: "An eminent cosmologist once advised me to forget all about very cold dust ....

He sounded plausible, as Cosmologists are apt to sound, but he was in fact totally wrong, as Cosmologists are apt to be ... Modest amounts of smoke [dust] can play merry hell with the decomposition of visible light profiles ... "

These were some of the key issues which drew approximately 100 astronomers from across the globe, to the University of the Witwatersrand in Johannesburg. The event in January 1996, was a conference entitled "New Extragalactic Per­spectives in the New South Africa: Changing Perceptions of the Morphology, Dust Content and Dust-Gas ratios in Galaxies". Much water had passed under the bridge since first-light of the Yale Observatory on our campus, in 1925 (page 578).

The conference was opened by the Deputy Vice-Chancellor for Research at the University, Professor J .P.F. Sellschop (Figure 1). Our Cabinet guest of honour at the conference banquet was Dr. Ben Ngubane, Minister of Arts, Culture, Science and Technology in Parliament. Delegates found Dr Ngubane's banquet address to be most thought provoking and will long be remembered as a conference high­light (Figure 2). A letter received from President Nelson Mandela was read out at the conference, and appears in this volume. Delegates heeded the President's recommendation to relax after our packed week of deliberations (colour plate 16)!

The Scientific Organizing Committee (SOC) was formed in late 1994, and in January /February of 1995 - one year in advance of the conference - the SOC members voted for all the speaker categories. Every SOC elected speaker agreed to provide a camera-ready copy of their talk at the Registration Desk. A revised version was permitted to be sent in by late February 1996, one month after the conference.

The ordering of the papers contained in these Proceedings essentially follows the order of presentation during the conference week. A notable exception is that of Gordon Stacey, who suffered a severe disk-crash at Cornell; with the granting of extra time to prepare his camera-ready copy, Dr Stacey's contribution could then only be accomodated at the end of the oral presentation section. We also very much regret that Dr Michael Fall was unable to submit a camera-ready copy of his talk, in time for the Proceedings. We are extremely grateful to Dr E. de Geus and /(L UWER for the inclusion of a set of sixteen pages of colour plates.

Professor Disney also wisely reminded us as Editors, that conference proceed­ings are invariably only as valuable as the degree to which conference interactions are reflected. Special steps were taken to ensure that these Proceedings could con­tain over 35 printed pages of the very lively and exciting interactions and discus­sions we all enjoyed together. A television crew filmed the live 'Eyes to the Future' Panel-Audience discussion, for transcription into Latex and finally into KL UWER style format. Our Chairpersons and Panelists are to be thanked for the great effort and care with which they undertook their responsibilities .

• The principal sponsor of the conference was the Anglo-American and de Beers Chairmans' Fund Educational Trust. Without the astronomical vision of Chairman Michael O'Dowd (Figure 1), this conference would never have been possible. Mr O'Dowd, we salute you. Mrs. Margaret Keeton and the Board of Trustees, we thank you. We appreciate that cold cosmic dust grains at temperatures of -250°C in galaxies billions of kilometres away may, at first glance, seem rather far removed from your gold-mining and diamond activities ... but as Dr. Duccio Macchetto and

PREFACE xvii

hyure 1. Top: The meeting of two ChaIrmen. 'Chairman Mayo ' Greenberg (top nght) meets Chairman Michael O'Dowd (top left). Mr O'Dowd is the Chairman of the An­glo American & De Beers Chairmans' Fund Educational Trust. Bottom: Professor JPF Sellschop, Deputy Vice-Chancellor for Research at the University (bottom left) in deep discussion with Dr L Alberts (bottom right) of the LOC.

xviii PREFACE

Figure 2. Top: Professor Paul Hodge (right) meets Cabinet Minister Ben Ngubane (left). Professor David Block (center) looks on. Minister N gubane is the Cabinet Minister of Arts, Culture, Science & Technology. Bottom: Professor Mike Disney (left) emphasizes a point to Minister Ngubane, while Professors David Block, Ron Allen and Brent Tully attentively listen.

PREFACE xix

... but as Dr. Duccio Macchetto and Dr. Dale Cruikshank reminded us at the conference, without exploding stars there would be no diamonds!

• Our deep gratitude to the University of the Witwatersrand for their financial support. In particular, we gratefully acknowledge financial support from the fund of the Deputy Vice-Chancellor for Research as well as from Professor R. Crewe, Dean of the Faculty of Science, at the University. We also thank members of our Departmental Conference Review Committee, Professor C.J. Wright (Head of the Department of Computational and Applied Mathematics), Professor D.P. Mason and Dr F. Mahomed for their constructive input.

• We are most indebted to the Foundation for Research Development for their wpp~. .

• As interest in our conference grew beyond all initial expectations, SASOL and TRANSNET provided a Pentium processor with modem to streamline the editing of the papers in these Proceedings.

• Cellular communication with the conference organizing team was facilitated by ERICSSON and VODACOM.

• To Mr P. Kruger and Mr R. Hugo of SASOL, to Dr M. de WaalofTRANSNET, to Mr M. Levitt of Ericsson and to VODACOM: our words of thanks cannot ade­quately express our deepest appreciation for the tremendous infrastructure you so graciously provided.

A special word of thanks, too, to: • Liz Block, wife of David Block, for her pillar of support during the preceed­

ing 15 months of conference preparation. There were some tense moments, such as when Kristen Sellgren arrived with no clothes 1 , but Liz stepped into action immediately!

• Ebrahim Momoniat. A note of great appreciation to Ebrahim was recorded at the conference banquet.

• All members of the SOC and LOC. • De Wet Ferreira for so willingly travelling to the University from Pretoria

on innumerable occassions to assist us with the immense task of collation before the Editorial process could begin.

• Traci Hanson of Rennies Travel, and Shirley Irish, Lady Warden of the Sun­nyside Residence at Wits University. As Dr Ron Allen emphasized in his vote of thanks, their dedication and professionalism left an indelible impression on Us all. Mrs. Irish even delayed taking her retirement in order to assure that the accomo­dations and arrangements at Sunnyside Residence would be the best possible!

• Mr Mark Irvine (Corporate Communications Department of the Anglo­American Corporation of SA) for the printing of the conference programme (see colour plate 1) and the printing of our conference logo for the conference wine bottles. And to Lauren Wilson and her team for the the streamlining of all pre­sentations at the University's Planetarium.

• Mrs Florence Goetze, secretary to DLB. • Mr S. Hlubi and Mr G. Lock, computer network specialists. • Mr P. van Huyssteen and Mr P. Liebenberg. • Dr Jack Flaks and Mrs Audrey Flaks. • The staff of our Central Graphics Unit - Colin Emslie, Jo Waltham, Natalie

Scrooby, Anna Michaelides, Bernice Fonseca, Gora J adwat, Joseph Moutloatsi

1 Her luggage had been mislaid enroute from the USA to Africa.

xx PREFACE

and Vasu Naidoo - your assistance has been invaluable. Our deep gratitude too, to Andy Blake and John Page .

• The South African dried fruit association (SAD) for the provision of South African dried fruits, and SATOUR for providing SA tourism material.

• Photographers Khashifa Jappie and Jo Waltham for securing our conference photographs and, in particular, the informal 'candid shots'. The group photo­graph was taken by Fidos Kleovoulou. The photograph of President Mandela is copyrighted by Karina Turok and reproduced by permission.

The dust veil is being lifted, and lifted dramatically. We live in a universe filled with New Cosmic Perspectives. From the photographic work of Draper, to unprece­dented insights with instruments sensitive to the infrared and the (sub )millimeter. It is with the express aim of trying to captivate the tremendous scientific exper­tise and thinktank of that great cold dust-morphology conference week at the University of the Witwatersrand, that we submit these Proceedings to the greater scientific community.

David L. Block J. Mayo Greenberg Johannesburg and Leiden 20 June, 1996.

Union Buildings Private Bag X1OO0 Pretoria 0001 Tel: (012) 319-1500

MESSAGE FROM PRESIDENT MANDELA

I extend a warm welcome to you all on the occasion of the International Astrophysics Conference.

Yours is a branch of science which has occupied the mind of every great scientist from Aristotle to Einstein. It is a noble pursuit indeed, and one which fundamentally enriches human knowledge about our habitat and our history.

We are honoured to have had South Africa selected as the venue for the Conference. We hope you will be able to find some time to relax and enjoy our beautiful country,

We wish you every success in your deliberations,

Nelson Mandela President of the Republic of South Africa

January 1996

PHOTOGRAPH: KARINA TUROK