When Galaxies Were Born: The Quest for Cosmic Dawn 9780691241678

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W H E N G A L A X I E S ­W E R E B O R N

WHEN GALAXIES ­W ERE BORN t h e qu e st for cosm ic daw n

RICHARD S. ELLIS

pr i nce­t on u n i v e r sit y pr e ss pr i nce­t on a n d ox for d

Copyright © 2022 by Prince­ton University Press Prince­ton University Press is committed to the protection of copyright and the intellectual property our authors entrust to us. Copyright promotes the pro­gress and integrity of knowledge. Thank you for supporting ­free speech and the global exchange of ideas by purchasing an authorized edition of this book. If you wish to reproduce or distribute any part of it in any form, please obtain permission. Requests for permission to reproduce material from this work should be sent to permissions@press​.­princeton​.­edu Published by Prince­ton University Press 41 William Street, Prince­ton, New Jersey 08540 99 Banbury Road, Oxford OX2 6JX press​.­princeton​.­edu All Rights Reserved Library of Congress Cataloging-in-Publication Data Names: Ellis, Richard S. (Richard Salisbury), 1950– author. Title: When galaxies were born : the quest for cosmic dawn / Richard S. Ellis. Description: Princeton, New Jersey : Princeton University Press, [2022] |   Includes bibliographical references and index. Identifiers: LCCN 2022002210 (print) | LCCN 2022002211 (ebook) |   ISBN 9780691211305 (hardback) | ISBN 9780691241678 (ebook) Subjects: LCSH: Galaxies—Formation. | Cosmology. | Astronomy—Observations. |   BISAC: SCIENCE / Space Science / General | SCIENCE / Space Science / Astronomy Classification: LCC QB857 .E45 2022 (print) | LCC QB857 (ebook) |   DDC 523.1/12—dc23/eng20220524 LC record available at https://lccn.loc.gov/2022002210 LC ebook record available at https://lccn.loc.gov/2022002211 British Library Cataloging-­in-­Publication Data is available Editorial: Ingrid Gnerlich and Whitney Rauenhorst Production Editorial: Kathleen Cioffi Text and Jacket Design: Karl Spurzem Production: Jacqueline Poirier Publicity: Sara Henning-­Stout and Kate Farquhar-­Thomson Copyeditor: Maia Vaswani Jacket images: (Top) Hubble views a cosmic Interaction, NASA. (Bottom) Mauna Kea Observatories by Julian Abrams This book has been composed in Arno Pro with Trade Gothic Next Printed on acid-­free paper. ∞ Printed in the United States of Amer­i­ca 10 ​9 ​8 ​7 ​6 ​5 ​4 ​3 ​2 ​1

CONTENTS

List of Illustrations

vii

Preface

xiii

Abbreviations

xvii

1 Out into Space

1

2 ­Grand Time Machines

13

3 Palomar: The Perfect Machine

29

4 The Anglo-­Australian Revolution

49

5 La Palma: La Isla Bonita

79

6 A Golden Era: Synergies with Hubble Space Telescope

109

7 The Mighty Keck Telescopes: Lifting the Curtain

135

8 Entering the Reionisation Era

153

9 The Arrival of the Euro: A Glimpse of Cosmic Dawn

173



Epilogue: A Promising ­Future

199

Illustration Credits

211

Index

217

v

I L L U S T R AT I O N S

Figures 0.1. The most distant known galaxy versus publication date in terms of its redshift and the age of the universe when the galaxy is being observed

xiv

3.1. The end of the road for the Hubble diagram of brightest cluster galaxies

42

4.1. A small portion of the photographic plate taken by Bruce Peterson at the AAT and a contour map resulting from the pro­cessing of this area by the Cambridge APM group

59

4.2. Measuring-­machine studies of photographic plates in the 1970s

59

4.3. The redshift distribution n(z) of the AAT surveys indicated a no-­evolution distribution despite a substantial excess in the number counts

69

5.1. The telescopes at the Observatorio de Roque de Los Muchachos on the summit of the island of La Palma

80

5.2. State of the art ­after the LDSS-2 redshift survey undertaken at the WHT in 1994

88

5.3. Results from the Canada-France Redshift Survey

90

5.4. The wide range in brightness probed over the redshift range 0  1 galaxies. It published its results in an impressive series of 14 highly detailed articles from 1995 to 1997, which had a large impact in the astronomical community. Scarcely a month went by when ­there ­wasn’t yet another paper by the CFRS team! By virtue of the group’s dif­fer­ent se­ lection method, it demonstrated that t­ here was ­little evolution in the quiescent population, but confirmed our finding that evolution in the star-­forming population was largely occurring in the low-­luminosity systems. In a summary paper the team claimed (rather proudly) that “the picture of galaxy evolution presented h­ ere pre­sents no inconsistencies with the very much smaller samples . . . ​selected in other wavebands” (i.e., our modest efforts!).3 The CFRS survey demonstrated to many of us what could be accomplished by a large, well-­coordinated team. Observational astronomy was, in the 1990s, transitioning from proj­ects undertaken by traditionally small teams such as mine—­typically a professor, students, and postdocs in one institution—to t­ hose involving a consortium of leading astronomers spread across a number of institutions. While the CFRS team had only five se­nior players, ambitious surveys would soon involve teams of 20 se­nior astronomers or more. Although I fought this trend as long as I could, preferring to work only with colleagues in my own institution (or former members of my group who had recently moved elsewhere), the trend to bigger teams has continued. Many observatories, including Hubble, Spitzer, and ground-­based facilities run by the Eu­ro­pean Southern Observatory (chapter 9), now regularly solicit what are termed “legacy,” “trea­sury,” or “large” proposals, promising over 10 times the traditional allocations of observing time, sometimes spread over 2 or 3 years, in order to encourage ambitious science programmes. This has led to the formation of large multinational teams where each participating member has a predetermined role in the data pro­cessing 3. Th ​ e Canada-­France Redshift Survey. VI. Evolution of the Galaxy Luminosity Function to z ~ 1, S. J. Lilly, L. Tresse, F. Hammer, D. Crampton, and O. Le Fèvre, Astrophysical Journal, vol 455 (1995), p123.

92  c h a p t e r 5

and/or the scientific exploitation. It is not always easy to ensure that students and postdocs—­those similar to Tom Broadhurst, Matthew Colless, and Karl Glazebrook—­can demonstrate their skills and thereby establish their ­careers in such large teams, which are nearly always led by se­nior astronomers safeguarded by permanent positions. Admittedly, however, a new generation of astronomers has emerged that is enthusiastic about participating in such large teams, which, if properly managed, can both be more inclusive and offer unique opportunities to share in impor­tant discoveries. Unable to compete with the CFRS survey at the faint end, I thought it would be advantageous to increase the galaxy redshift sample at intermediate brightness, extending our e­ arlier surveys over wider areas of sky. This would reduce the effect of clustering patterns in the galaxy distribution and improve the range of galaxy luminosities sampled at each redshift. Since the Autofib fibre positioner on the AAT encompassed a field of view on the sky over 10 times larger than the multi-­slit spectrographs at the CFHT and WHT, it was the ideal instrument for this task. Over a number of runs in Australia, we secured over 1000 redshifts in 32 in­de­pen­dent fields at depths similar to Tom Broadhurst’s original fibre survey. Together with the fainter surveys, this led to a new cata­logue of over 1700 redshifts spanning an unpre­ ce­dented range in brightness of a f­ actor 100,000. Our resulting article was published at more or less the same time as the final CFRS papers and similarly concluded that ­there was no change in the quiescent population to at least a redshift z ~ 0.5, but that t­ here was a significant increase in activity in the sub-­luminous star-­forming population. We concluded that “the steepening of the [faint portion of the] luminosity distribution with lookback time is of the form originally postulated by Broadhurst, Ellis and Shanks and is a direct consequence of the increasing space density of blue star-­forming galaxies at moderate redshifts” (figure 5.4).4 4. ​Autofib Redshift Survey. I. Evolution of the Galaxy Luminosity Function, R. S. Ellis, M. Colless, T. Broadhurst, J. Heyl, and K. Glazebrook, Monthly Notice of the Royal Astronomical Society, vol 280 (1996), p235.

L a Pa l m a   93 –1

–2

Galaxies per unit volume (log scale)

–3 0.02 < z < 0.15 0.15 < z < 0.35 0.35 < z < 0.75

–4 –22

–20

–18

–16

–14

Luminosity figure 5.4. The wide range in brightness probed over the redshift range 0