Santa Cruz Summer Workshops in Astronomy and Astrophysics S.M. Faber Editor

Nearly Nonnal Galaxies From the Planck Time to the Present

The Eighth Santa Cruz Summer Workshop in Astronomy and Astrophysies July 21-August 1, 1986, Liek Observatory

With 133 Illustrations

Springer-Verlag New York Berlin Heidelberg London Paris Tokyo S. M. Faber Department of Astronomy University of California Santa Cruz, CA 95064, USA

Library of Congress Cataloging-in-Publication Data Santa Cruz Summer Workshop in Astronomy and Astrophysics (8th: 1986) Nearly normal galaxies. (Santa Cruz summer workshops in astrophysics) I. Galaxies-Congresses. 2. Astrophysics- Congresses. I. Faber, Sandra M. 11. Title. 111. Series. Q8856.S26 1986 523.1' 12 87-9559

© 1987 by Springer-Verlag New York Inc. Softcover reprint ofthe hardcover 1st edition 1987 All rights reserved. This work may not be translated or copied in whole or in part without the written permission ofthe publisher (Springer-Verlag, 175 Fifth Avenue, New York, New York 10010, USA), except for bI1ef excerpts in connection with reviews or scholarly analysis. U se in connection with any form of information storage and retrieval. electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc. in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. Permission to photocopy for internal or personal use, or the internal or personal use of specific c1ients, is granted by Springer-Verlag New York Inc. for libraries registered with the Copyright Clearance Center (CCC), provided that the base fee of $0.00 per copy, plus $0.20 per page is paid directly to CCC, 21 Congress Street, Salem, MA 01970. U.S.A. Special requests should be addressed directly to Springer-Verlag New York, 175 Fifth Avenue, New York, New York 10010, U.S.A. 96521-1/1987 $0.00 + .20

987654321 ISBN-13:978-1-4612-9145-9 e-ISBN-13978-1-4612-4762-3 DOI: 10.1007/978-1-4612-4762-3 ALBERT EDWARD WHITFORD

On October 22, 1985, Albert Whitford celebrated his eightieth birthday.

Whitford is honored as one of the founding fathers of photoelectric photometry, the technique that transformed twentieth-century astronomy from a qualitative to a quantitative science. Together with collaborator and mentor Joel Stebbins, Whit• ford began, in the early 1930s, a systematic survey of stellar and galaxy photometry that initiated the modern era of this subject. Concepts encountered in this early work included interstellar extinction, color excess, effective wavelengths, galaxy surface-brightness profiles, and K-corrections. Techniques developed by Whitford and Stebbins to deal with these have become such apart of the lore of observational astronomy that their origins to today's students are obscure. Whitford's own con• tribut ion to this work lay principally in the perfection of the equipment, notably in low-noise amplification of the signal. Joining Stebbins as a junior collaborator and fresh Ph.D. (in physics from Wisconsin), Whitford exercised skills as an instru• mentalist so outstanding that, within a short while, Stebbins came to regard hirn as indispensable. vi Albert Edward Whitford

World War II intervened, and Whitford spent five years in war work at the

MIT Radiation Laboratory. After the war, he returned to Washburn Observatory at

Wisconsin, where he shortly became Director and Full Professor. In 1958 he moved west to become Director of the Liek Observatory. There his technieal acumen enabled hirn to take charge of the 120-inch telescope project when it was far behind schedule and get it rapidly back on track. Within little more than a year the telescope was in full operation and continues to this day as the mainstay of the optieal astronomy program of the University of California.

At about this time Whitford wrote what is probably his most quoted paper setting forth a standard interstellar extinction curve, the so-called Whitford law.

In the 1960s he was president of the Ameriean Astronomieal Society and chaired the first National Academy of Sciences review on the progress and needs of observa• tional astronomy. Ground Based Astronomy: A Ten Year Program was so weil and wisely written that it became a model for N AS discipline reviews and has inspired two subsequent astronomie al reviews in a pattern that now threatens to become established custom. Rereading the Whitford Report, one finds that its recommen• dations were closely followed and that its vision shaped the pattern for the technieal advancement of observational astronomy from the 19605 onward.

In 1973, Albert Whitford became Emeritus Professor / Astronomer, but with retirement his scientific productivity if anything began to increase. In a pro• fession renowned for the vigor of its older practitioners, Whiford's achievements after retirement inspire the greatest admiration. A major early impetus for the

Stebbins-Whitford photoelectrie photometry program was an interest in galaxy stellar populations and in quantifying comparisons between galaxy spectral-energy Albert Edward Whitford Vll distributions and those of stars. In the 1970s Whitford realized that the nuclear bulge of the Galaxy provided a unique opportunity to study, star-by-star, a strong• lined, old stellar population like that found in elliptical galaxies and spiral bulges.

Since then, he and his collaborators Jay Frogel, Mike Rich, and Don Terndrup have been collecting fundamental data - colors, magnitudes, and spectra - of bulge stars.

As in all great enterprises, this one has not been without its surprises, turning up giant branch stars that are simultaneously metal-rich but rather blue. The bulge studies are clearly yielding unique data on old stars of fundamental importance to population syntheses of external galaxies.

In view of Whitford's age, it is not surprising that his recent collaborators are all younger than he, but it is significant that two of them - Rich and Terndrup

- were graduate students. Albert Whitford seems to have had a special affinity for graduate students in his emeritus years. His office was and is a place students can go to find encouragement and a sympathetic ear. Several Lick students, including

Alan Dressler, David Burstein, and Nick Suntzeff, remember Albert for the benign infiuence he has had on their graduate careers.

In recognition of his lifetime of achievement in the areas of photoelectric photometry and galactic stellar populations, the first session of this year's Santa

Cruz Workshop is enthusiastically dedicated to Albert Edward Whitford.

S. M. Faber

July 1986 Preface

It is sometimes said that astronomy is the crossroads of physics. In the same spirit, it can forcefully be argued that galaxies are the crossroads of astronomy. Internal pro ces ses within galaxies involve all of the fundamental components of astrophysics: stellar evolution, star formation, low-density astrophysics, dynamics, hydrodynamics, and high-energy astrophysics. Indeed, one can hardly name an observational datum in any wavelength range on any kind of celestial object that does not provide a useful clue to galaxy formation and evolution.

Although internal processes in galaxies until recently occupied most of our attention, we now know that it is also vital to relate galaxies to their environment.

How galaxies congregate in larger structures and are in turn influenced by them are crucial questions for galactic evolution. On a grander level we have also come to regard galaxies as the basic building blocks of the universe, the basic units whereby the large• scale structure of the universe is apprehended and quantified. On a grander level still, we also believe strongly that galaxies are the direct descendents of early density

irregularities in the Big Bang. Galaxy properties are now viewed as providing a crucial constraint on the physics of the Big Bang and a vital link between the macroscopic

and microscopic structure of the universe.

A picture of galactic evolution as the crossroads of astronomy and cosmology

thus emerges very strongly - a melding of basic physics and astrophysics, an eclectic

borrowing of diverse observation al techniques, and the convergence of the very large

with the very small. To understand galaxies in all their ramifications clearly entails a

synthesis of the highest order. x Preface

Such a synthesis was the avowed goal of this summer's Santa Cruz Summer

Workshop on galaxies. The extended, two-week format allowed participants to cover essentially all of the major issues of current interest in galaxy formation and evolution

- from stellar evolution to cosmic strings and virtually everything in between. It was the first time, to my knowledge, that an organized meeting of such long duration was devoted to the subject, and the result was a more comprehensive, unified view than could be had from the usual two- or three-day conference.

This book, wh ich summarizes the morning talks by the invited speakers, is therefore of special value. The fifty-odd papers contained herein provide a remarkably complete snapshot of the field of galactic evolution as it exists in 1986. Most of the papers are excellent reviews that provide both student and professional alike with a convenient jumping-off place into the literature. Because of the wide range of topics covered, the volume mayaiso be useful as a collection of supplemental readings for graduate courses on galactic evolution. Special thanks are due to all the speakers for providing manuscripts of such uniformly high quality.

Readers will note that the present volume is the first of a new series. Since the last three Santa Cruz Workshops have produced proceedings in response to public demand, it seems that this is an idea that has taken permanent root. Accordingly, with the help of Springer-Verlag, we are intending to bring out a published summary of the morning sessions of future Summer Workshops as a regular activity.

In closing, it is worth noting the truly remarkable progress that has been

made in understanding galactic evolution over the past decade, to which the current

volume bears witness. A quick perusal of the Table of Contents reveals many papers

whose very titles would have been incomprehensible a bare five years ago. Thanks Preface xi to the injection of new ideas from particle physics and the stimulus of ever-grander observational programs, galactic evolution has recently experienced a rare quantum leap forward in understanding and insight.

One hopes fervently that this advance has not yet peaked but will continue in the years ahead with equal vigor. We look forward to the next Santa Cruz Workshop on galaxies, not too many years off, we hope, that will chronicle the next stage of our developing understanding.

S. M. Faber

Santa Cruz

December 1986 Acknowledgments

The Santa Cruz Astrophysies Workshops owe a great debt of gratitude to the several institut ions and individuals who make continued workshops possible. The major share of extramural financial support for this year's workshop was provided by generous grants from the NSF and NASA. Important additional support came from the Institute for Geophysies and Planetary Physies (IGPP) at Lawrence Livermore

National Laboratory and a local campus grant from the Natural Sciences Division.

We also gratefully acknowledge the continued dose cooperation of the Liek

Observatory. Although the workshops are financially and administratively indepen- dent of Liek, the Observatory provides invaluable assistance in lending facilities, per- sonnei, and moral support. We also could not manage without the help of the astron- omy graduate students, six of whom this year donated a great deal of their time and effort to the workshop.

Sandra Faber wishes especially to thank this year's Scientific Organizing Com- mit tee for their very able choiee of topies, speakers, and organization of the morning sessions. The members of this committee are listed in the Table of Contents under the session they chaired. Sandra M. Faber Workshop Organizer Sue Robinson Workshop Coordinator Pat Shand Production Manager Contents

Session 1 - Stellar Evolution in Galaxies 1 Robert P. Kraft, Chair

The Stellar Population of the Nuclear Bulge 3 Jay A. Frogel

Stellar Populations in Local Group Galaxies 10 L. L. Stryker

Star Formation in Colliding and Merging Galaxies 18 Fran<;ois Schweizer

Star Formation in Disks and Spheroids 26 Richard B. Larson

Star Formation in Disks: IRAS Results 36 Carol J. Persson

The Metallicity Distribution of the Extreme Halo Population 41 Timothy C. Beers

Session 2 - Small Objects 45 J. Huchra, Chair

Systematic Properties of Extragalactie Globular Clusters 47 David Burstein

Stellar Populations in Dwarf Spheroidals 57 Mare Aaronson

Blue Compact Dwarfs: Extreme Dwarf Irregular Galaxies 67 Trinh X. Thuan

Dwarf Galaxies and Dark Matter 76 Scott Tremaine xiv Contents

Session 3 - Galactic Structure and Dynamies: Observations 79 J. van Gorkum, Chair

Photometry and Mass Modeling of Spiral Galaxies 81 S. Kent

The Stellar Population at the Galactic Center 90 Marcia J. Rieke

Hot Gas Evolution in Nearly Normal Elliptical Galaxies 96 M. Loewenstein and W. G. Mathews

Hot Coronae Around Early Type Galaxies 109 Christine Jones

The Relative Masses of the Milky Way's Components, 116 the Ostriker-Caldwell Approach, and Differential Rotation Beyond the Solar Circle P. L. Schechter

Mass Models for Disk and Halo Components in Spiral Galaxies 121 E. Athanassoula and A. Bosma

Session 4 - Galactic Structure and Dynamies: Theory 127 K. Freeman, Chair

The Structure and Evolution of Disk Galaxies 129 R. G. Carlberg

The Effects of Satellite Accretion on Disk Galaxies 138 P. J. Quinn

Self-Regulating Star Formation and Disk Structure 144 Michael A. Dopita

Halo Response to Galaxy Formation 154 Joshua E. Barnes Contents xv

Session 5 - Global Parameters of Galaxies 161 S. M. Faber, Chair

Cores of Early-Type Galaxies: The Nature of Dwarf Spheroidal Galaxies 163 John Kormendy

Global Scaling Relations for Elliptical Galaxies and Implications for Formation 175 S. M. Faber, A. Dressler, R. L. Davies, D. Burstein, D. Lynden-Bell, R. Terlevich, G. Wegner

Musings Concerning the Possible Significance of Surface Brightness 184 Variations in Disk Galaxies Greg Bothun

The Luminosity Function: Dependence on Hubble Type and Environment 195 Bruno Binggeli

Core Properties of Elliptical Galaxies 207 Tod R. Lauer

Session 6 - Galaxies in Relation to Larger Structures 211 Avishai Dekel, Chair

Voids and Galaxies in Voids 213 Augustus Oemler, Jr.

The Large Scale Distribution of Galaxy Types 220 Martha P. Haynes

Coherent Orientation Effects of Galaxies and Clusters 227 S. Djorgovski

Galaxy Formation and Large Scale Structure 234 Simon D. M. White

Scenarios of Biased Galaxy Formation 244 Avishai Dekel

Biasing and Suppression of Galaxy Formation 255 M. Rees xvi Contents

Session 7 - Distant Galaxies 263 R. Kron, Chair

Stellar Populations in Distant Galaxies 265 G. Bruzual

Evolution of Cluster Galaxies Since z = 1 276 A. Dressler

Galaxies at Very High Redshifts (z > 1) 290 S. Djorgovski

Dynamics of Galaxies at Large Redshift: Prospects for the Future 300 Richard G. Kron

Session 8 - Dark Matter 311 Virginia Trimble, Chair

Dark Matter in Binary Galaxies and Small Groups 313 Virginia Trimble

Dark Matter in Dwarf Galaxies 317 K. C. Freeman

Dark Matter in Early-Type Galaxies 326 S. Michael Fall

What is the Cosmological Density Parameter Oo? 332 Amos Yahil

Fundamental Physics and Dark Matter 343 Katherine Freese

Session 9 - Galaxies Before Recombination 353 Joel Primack, Chair

Inflationary Universe Models and the Formation of Structure 355 Robert H. Brandenberger

Formation and Evolution of Cosmic Strings 367 Andreas Albrecht Contents xvii

The Quark-Hadron Phase Transition and Primordial Nucleosynthesis 378 Craig J. Hogan

Testing Cosmic Fluctuation Spectra 388 J. Richard Bond

Session 10 - Galaxies After Recombination 399 George BlumenthaI, Chair

Models of Protogalaxy Collapse and Dissipation 401 George R. BlumenthaI

Unstable Dark Matter and Galaxy Formation 413 Ricardo A. Flores

Halos and Angular Momentum Generation 421 C. S. Frenk

Cosmic Strings and the Formation of Galaxies 431 and Clusters of Galaxies N. Turok

Large Scale Drift and Peculiar Acceleration as Cosmological Tests 451 N. Vittorio & R. Juszkiewicz

Conference Summary 455 James E. Gunn 1986 xviii Workshop Participants 1986 Workshop Participants XIX xx 1986 Workshop Participants

1. Ray Carlberg 41. John Kormendy 81. Ed Langer 2. Brad Whitmore 42. Michael Strauss 82. Dave Burstein 3. Tony Tyson 43. Alar Toomre 83. Giuseppina Fabbiano 4. Colin Norman 44. Greg Bothun 84. U nidentified 5. Art Wolfe 45. George Blumenthai 85. Renzo Sancisi 6. Lucio Buson 46. Hyesung Kang 86. Michael Pierce 7. Mike Loewenstein 47. Richard Larson 87. Marcia Rieke 8. Sue Robinson 48. Dongsu Ryu 88. Augustus Oemler 9. Bill Mathews 49. Amos Yahil 89. Merle Walker 10. Albert E. Wbitford 50. Mare Davis 90. Richard Elston 11. J. Jesus Gonzalez 51. Ricardo Flores 91. David Seckel 12. Yehuda Hoffman 52. Tod Lauer 92. Gustavo Ponce 13. Erez Braun 53. Alan Dressler 93. E. Athanassoula 14. Edmund Bertschinger 54. Dave Carter 94. Roger Davies 15. Doug Richstone 55. Jim Mark 95. Sterl Phinney 16. Bill Forman 56. Christine Jones 96. David Band 17. Jim Gunn 57. Albert Bosma 97. J. Richard Bond 18 . Avishai Dekel 58. Ling Luan 98. Scott Tremaine 19. Josh Ba.rnes 59. Jo Ann Eder 99. Mike Fall 20. Simon White 60. Cedric Lacey 100. Carlos Frenk 21. Steve Kent 61. Jens Villumsen 101. Howard Bond 22. Gene Smith 62. Peter Quinn 102. Mare Postman 23. Peter Martin 63. Luis A. Aguilar 103. Edward Rosenblatt 24. Franc;ois Schweizer 64. Ken Freeman 104. Jay Frogel 25. Craig Hogan 65. Steve Shectman 105. Robert Kirshner 26. Richard Kron 66. Gustavo Bruzual 106. Brent Tully 27. Paul Shapiro 67. Manolis Plionis 107. Carol Persson 28. Neta Bahcall 68. Gerry Gilmore 108. Richard Shaw 29. Mare Aaronson 69. Rosie Wyse 109. Lloyd Robinson 30. Ofer Lahav 70. David Koo 110. Mark Henriksen 31. Sidney van den Bergh 71. Stefano Kasertano 111. Trinh Thuan 32. Paul Schecter 72. Jon Holtzman 112. John Tonry 33. Avery Meiksin 73. Colin McGill 113. David Spergel 34. Pat McCarthy 74. Jacqueline van Gorkom 114. Rick Pogge 35. Leonid Ozernoy 75. Gregory Shields 115. Bruce Carney 36. Paolo Salucci 76. Konrad Kuijken 116. Linda Stryker 37. Mike Dopita 77. Joel Primack 117. Kap-Soo Oh 38. Bruno Binggeli 78. Mark Yates 118. Sandra Faber 39. Alexander Kashlinsky 79. Adrian Melott 119. John Huchra 40. Michael West 80. Elaine Sadler 120. Timothy Beers Participants

PARTICIPANT INSTITUTION AARONSON. Mare Steward Observatory AGUILAR. Luis A. Smithsonian Center for Astrophysies ALBRECHT. Andreas Los Alamos National Labs ATHANASSOULA. E. Observatoire de Marseille. Franee BAHCALL. Neta Spaee Teleseope Seienee Institute BAND. David L. Lawrenee Livermore National Lab BARDEEN. James M. University of Washington BARNES. Joshua E. Institute for Advaneed Study BEERS. Timothy C. California Institute of Teehnology BERTSCHINGER. Edmund University of California. Berkeley BINGGELI. Bruno University of Basel. Switzerland BLUMENTHAL. George University of California. Santa Cruz BODENHEIMER. Peter University of California. Santa Cruz BOND. Howard E. Spaee Teleseope Scienee Institute BOND. J. Riehard University of Toronto. Ca na da BOSMA. Albert Observatoire de Marseille. Franee BOTHUN. Greg California Institute of Teehnology BRANDENBERGER. Rohl. University of Cambridge. England BRAUN. Erez Weizmann Institute of Scienee. Israel BRUZUAL. Gustavo Centro de Investigaeiones de Astronomia Venezuela BURKE. Bill University of California. Santa Cruz BURSTEIN. David Arizona State University BUSON. Lueio M. Osservatorio Astronomieo Padova. Italy xxii Participants

CARLBERG. Raymond Johns Hopkins University CARN EY. Bruce W. University of North Carolina CARTER. David Mount Stromlo and Siding Spring Obs. Australia CASERTANO. Stefano Institute for Advanced Study COURTEAU. Stephane University of California. Santa Cruz DAVIES. Roger L. Kitt Peak National Observatory DAVIS. Marc University of California. Berkeley DEKEL. Avishai Weizmann Institute of Science. Israel DJORGOVSKI. S. George Smithsonian Center for Astrophysics DOPITA. Michael A. Mount Stromlo and Siding Spring Obs. Australia DRAKE. Frank University of California. Santa Cruz DRESSLER. Alan Mt Wilson and Las Campanas Obs. EDER. Jo Ann Yale University ELSTON. Richard Steward Observatory FABBIANO. Giuseppina Smithsonian Center for Astrophysics FABER. Sandra M. Lick Observatory FALL. Michael Space Telescope Science Institute FLORES. Ricardo A. Brandeis University FORMAN. Bill Smithsonian Center for Astrophysics FREEMAN. Ken Mount Stromlo and Siding Spring Obs. Australia FREESE. Katherine University of California. Santa Barbara FRENK. Carlos S. University of Durham. England FRIEL. Eileen University of California. Santa Cruz FROGEL. Jay A. Kitt Peak National Observatory FULLER. George M. Lawrence Livermore National Lab GILMORE. Gerry Institute of Astronomy. England GONZALEZ. J. Jesus University of California. Santa Cruz GOODRICH. Bob University of California. Santa Cruz Participants XXlll

GRIEST. Kim University of California. Santa Cruz GUNN. James E. Princeton University HABER. Howard University of California. Santa Cruz HARTMANN. Dieter University of California. Santa Cruz HAYNES. Martha P. Cornell University HELLINGER. Douglas University of California. Santa Cruz HENRIKSEN. Mark Space Telescope Scienee Institute HO. Darwin D.-M. Lawrence Livermore National Lab HOFFMAN. Yehuda University of Pennsylvania HOGAN. Craig Steward Observatory HUCHRA. John Smithsonian Center for Astrophysics ILLINGWORTH. Garth Space Teleseope Science Institute JONES. Christine Smithsonian Center for Astrophysics KANG. Hyesung University of Texas KASHLlNSKY. Alexander National Radio Astronomy Observatory KENT. Stephen Smithsonian Center for Astrophysics KING. Ivan R. University of California. Berkeley KIRSHNER. Robert P. Smithsonian Center for Astrophysics KOO. David C. Spaee Teleseope Scienee Institute KORMENDY. John Dominion Astrophysical Observatory Canada KORYCANSKY. Don University of California. Santa Cruz KRAFT. Robert P. Liek Observatory KRON. Riehard Yerkes Observatory KUIJKEN. Konrad Institute of Astronomy. England LACEY. Cedric G. Princeton University Observatory LAHAV.Ofer Institute of Astronomy. England LARSON. Richard B. Yale University LAUER. Tod R. Princeton University LOEWENSTEIN. Michael University of California. Santa Cruz LUAN. Ling University of California. Santa Cruz xxiv Participants

MARK. James W-K. Lawrence Livermore National Lab MATHEWS. Grant J. Lawrence Livermore National Lab MATH EWS. William G. University of California. Santa Cruz MElKSIN. Avery University of California. Berkeley MELOTT. Adrian L. University of Kansas MOREA. Cristiria Dalle Ore University of California. Santa Cruz MURRAY. Stephen University of California. Santa Cruz McCARTHY. Patrick J. University of California. Berkeley McGILL. Colin Institute for Advanced Study NORIEGA-CRESPO. A. University of California. Santa Cruz NORMAN. Colin Space Telescope Science Institute OEMLER. Augustus Yale University OH. Kap-Soo University of California. Santa Cruz OSTERBROCK. Donald E. Lick Observatory OZERNOY. Leonid Lebedev Physical Institute. USSR PERSSON. Carol California Institute of Technology PHINNEY. E. Sterl California Institute of Technology PIERCE. Michael J. Institute for Astronomy. Hawaii PLiONIS. Manolis University of Sussex. England POGGE. Richard University of California. Santa Cruz PONCE. Gustavo A. University of Texas at Austin POSTMAN. Marc Smithsonian Center for Astrophysics PRIMACK. Joel University of California. Santa Cruz QUINN. Peter Space Telescope Science Institute REES. Martin Institute of Astronomy. England RICHSTONE. Douglas O. University of Michigan RIEKE. Marcia Steward Observatory ROBINSON. Lloyd B. Lick Observatory ROOD. Herbert J. Institute for Advanced Study RYU. Dongsu University of Texas Participants xxv

SADLER. Elaine M. Kitt Peak National Observatory SALE. Ken Lawrence Livermore National Lab SALUCCI. Paolo ISAS. Italy SANCISI. Renzo Kapteyn Laboratorium. Netherlands SCHECHTER. Paul Mt Wilson and Las Campanas Obs. SCHWEIZER. Francois Dept of Terrestrial Magnetism SECKEL. David University of California. Santa Cruz SHAPIRO. Paul University of Texas SHAW. Dick Lick Observatory SHECTMAN. Stephen Mount Wilson Observatory SHER. Marc University of California. Santa Cruz SHIELDS. Gregory University of Texas SILK. Joseph University of California. Berkeley SMITH. Harding E. University of California. San Diego SPERGEL. David Institute for Advanced Study STEBBINS. Albert University of California. Berkeley STRAUSS. Michael University of California. Berkeley STRINGFELLOW. Guy S. University of California. Santa Cruz STRYKER. Linda L. Arizona State University SUNTZEFF. Nicholas Cerro-Tololo Interamerican Observatory Chile SWENSON. Fritz J. University of California. Santa Cruz TERNDRUP. Don University of California. Santa Cruz THUAN. Trinh X. Leander McCormick Observatory TOHLINE. Joel E. Louisiana State University TONRY. John Massachusetts Institute of Technology TOOMRE. Alar Massachusetts Institute of Technology TREMAINE. Scott University of Toronto. Canada TRIMBLE. Virginia University of California. Irvine and University of Maryland TULLY. Brent Institute for Astronomy. Hawaii xxvi PaIticipants

TUROK, N. Imperial College, England TYSON, Tony AT & T Bell Labs van den BERGH, Sidney Dominion Astrophysical Observatory van GORKOM, Jacqueline Princeton University Observatory VEILLEUX, Sylvain University of California, Santa Cruz VILLUMSEN, Jens V. California Institute of Technology VITTORIO, Nicola University of California, Berkeley WALKER, Merle Lick Observatory WEST, Michael J. Yale University WHITE, Simon Steward Observatory WHITFORD, Albert E. Lick Observatory WHITMORE, Brad Space Telescope Science Institute WOLFE, Arthur M. University of Pittsburgh WOOSLEY, Stan University of California, Santa Cruz WYSE, Rosemary F. Space Telescope Science Institute YAHIL, Amos State University of New York YATES, Mark G. Royal Observatory, Scotland