The Nature and Evolution of High Redshift Dusty Star Forming Galaxies Joshua Greenslade Astrophysics Group Department of Physics Imperial College London Thesis submitted for the Degree of Doctor of Philosophy to Imperial College London - 2018 - Abstract DSFGs dominate the cosmic star formation rate (SFR) at z > 0:7, are 2 - 3 orders of magnitude −1 more populous at z = 2 than locally, and have SFRs of tens to thousands of M yr . Despite their prodigious SFR, they are heavily dust obscured, with estimates suggesting that optical/UV surveys alone miss half the star formation in the Universe. Furthermore, DSFGs are believed to be the evolutionary progenitors to the massive elliptical galaxies that today inhabit the cores of massive galaxy clusters. DSFGs however remain poorly constrained, with few constraints on their contribution to the cosmic SFR density above z > 4, disagreement over whether single- dish observations accurately reflect the underlying population, and uncertainty about DSFGs in clusters, particularly whether they trace massive overdensities at their epoch. This thesis presents a series of results that set out to address some of these questions. To begin with, and by cross-matching Planck and Herschel data, we identify 27 candidate protoclusters by searching for overdensities of DSFGs. Their colours indicate they likely lie at z = 2 − 3, their flux density is 3x brighter than predicted from models, and fitting modified blackbodies to −1 their photometry suggests they have total SFRs of several thousand M yr . We additionally present the results of an interferometric program targeting 36 single-dish DSFGs at z ∼ 4. We assess their multiplicity, finding that whilst ∼ 45% are blends of multiple sources, there are a number of highly luminous, possibly lensed, singular sources. Finally, we present the serendipitous detection of a SPIRE dropout, a source detected at 850 µm but not at any shorter wavelength, likely at z > 6, and we discuss the application of its selection to wider surveys. In closing, we discuss the future of FIR/sub-mm astronomy, new directions of the work begun here, and the challenges that remain for the field. 1 2 Acknowledgements Of all of the words in this thesis, these are the hardest to write. To adequately credit all those who have borne me through to this point is simply an impossible task. Nevertheless, several of those countless individuals deserve space within these few lines. First and foremost, I would like to thank my supervisor, Dave Clements, whose infinite patience, guidance, and care have not only supported me through this journey, but whose raw passion and clear enjoyment of his subject are constantly uplifting. Quite simply, without Dave, none of this would have been possible. I also wish to pay thanks to my academic brother Tai-An, whose insight and determination serve as an inspiration every day, and whose comments and questions have helped me to refine and polish every aspect of this thesis. I cannot pass by without mentioning my other academic siblings, in particular those who shared so much of this journey with me. Ciar^an,Charlotte, Claude, Rhys, Hik and Nat, with whom I have all shared so my laughs, jokes, pints, puzzles and emergency tea, thank you for everything and for making this journey endurable. Special mention should also go out to everyone involved in the planetarium shows (thanks Cat for dumping that on my desk at the end of first year!), in particular to Tom, Dan, Charlotte, Hik, George, Wahid, Emily, and everyone who've I've inevitably forgotten to mention and who've been involved. Without you all, it would never had gotten to the point it is now, so thank you. It goes too, without saying, my thanks to those involved and who enjoy the cryptic puzzle group that has been springing up in the interaction area over the last few years. It is my great hope that someone else takes over the posting of new puzzles and clues, and my thanks to all who indulged in these interesting titbits. To my friends, too numerous to mention but too extraordinary not to, yours has been the guiding light; each and every one of you a shimmering, blazing star in your own right, against the backdrop of what has been a long, dark nights sky for me. Yours, all of yours, are the lights which have guided me, comforted me, and given me hope. Special mention to those that have suffered me most: Henry Wearing, whose honesty and kinship gave me joy at the lowest of points, James Hickson, who together in mutual suffering we shared laughter and drunken despondence at our lot, Heather Thomas, whose shining love, altruistic care, and unwavering patience with my ups and downs have carried me more than any other through the last few years, and finally Chris Love, for whom no earthen language, script or motion possess the requisite intricacy to describe my unceasing gratitude for your friendship. 3 Finally, I would like to thank my brother Chris, my sister Faye, my mother Debra, my father Ian, my aunt NJ, my cousin Kai, my grandma Joan (Guv), and my grandma Valerie. They have all shown an inhuman level of patience with me as I've been writing this, picking up the slack whilst I effectively dropped off the radar for six months. Their continued words and actions of kindness and compassion serve as a constant reminder that whilst the Universe may hold infinite possibility, there is no place I would rather be than within their familial embrace. 4 Dedication For Ian Stuart Greenslade. A teacher of unparalleled passion, A inquirer of unequalled eagerness, And a father of indisputable devotion, Whose hope, curiosity, and love, Thunder into the cosmos. 5 The copyright of this thesis rests with the author. Unless otherwise indicated, its contents are licensed under a Creative Commons Attribution-Non Commercial 4.0 International Licence (CC BY-NC)1. Under this licence, you may copy and redistribute the material in any medium or format. You may also create and distribute modified versions of the work. This is on the condition that: you credit the author and do not use it, or any derivative works, for a commercial purpose. 1https://creativecommons.org/licenses/by/4.0/ 6 The work contained herein is the result of the authors own work. Any work that is not the authors own is correctly referenced and attributed to its original source. 7 8 Contents Abstract 1 Acknowledgements 2 Copyright Declaration 6 Declaration of Originality 7 1 Introduction 22 1.1 The Infrared Sky . 22 1.1.1 Cosmology . 22 1.1.2 The Cosmic Infrared Background . 24 1.1.3 Local Infrared Bright Galaxies . 27 1.2 Infrared Astronomy . 32 1.2.1 Atmospheric Opacity . 32 1.2.2 Single Dish Observations . 33 1.2.3 An Extremely Negative K-correction . 36 1.2.4 Instrumentation . 38 9 10 CONTENTS 1.3 Dusty Star Forming Galaxies . 40 1.3.1 Redshift Distributions . 41 1.3.2 The Luminosity Evolution of Dusty Star Forming Galaxies . 44 1.3.3 Scaled up Local (U)LIRGs . 47 1.3.4 Multiplicity and Mergers . 48 1.3.5 Environment . 50 1.3.6 Models of DSFGs . 51 1.3.7 Our Current Understanding of High-z DSFGs . 53 1.4 This Thesis . 54 2 Protoclusters of DSFGs at z > 1 57 2.1 Introduction and Motivation . 57 2.2 The Data . 64 2.2.1 The Planck Catalogues of Compact Sources . 65 2.2.2 The Herschel Extragalactic Legacy Surveys . 69 2.3 Selection and Identification of Sources . 73 2.3.1 Source Selection . 74 2.3.2 Source Identification . 76 2.3.3 Diffuse and Dominated Sources . 80 2.3.4 Variations between the ERCSC, PCCS1 and PCCS2 . 83 2.4 Photometry . 84 2.4.1 Are the Planck and Herschel Photometry Consistent? . 85 CONTENTS 11 2.4.2 Are the Detected Herschel Sources Enough to Match the Planck Flux Density? . 87 2.5 Colours . 90 2.5.1 Planck Colours . 90 2.5.2 Herschel Colours . 95 2.6 The Candidate Protoclusters . 98 2.6.1 Line of Sight Effects . 98 2.6.2 Properties of the Protocluster Candidates . 100 2.6.3 Simulations of DSFGs in Clusters . 113 2.7 Discussion . 115 2.7.1 The HeLMS Field . 116 2.7.2 The Nature of the Planck Sources . 116 2.7.3 The Nature of the Candidate Protoclusters . 121 2.7.4 Future Work . 122 2.8 Conclusions . 123 3 Multiplicities of 500 Micron Risers 126 3.1 Introduction and Motivation . 126 3.2 Target Selection . 129 3.3 Methods . 132 3.3.1 Interferometry . 132 3.3.2 Data Reduction . 134 12 CONTENTS 3.3.3 Source Extraction . 135 3.3.4 The Detected Sources . 148 3.4 Extraction of Physical Properties . 153 3.5 Discussion . 158 3.5.1 Number Counts . 158 3.5.2 Lensing . 159 3.5.3 Blended Sources . 160 3.5.4 Extreme Luminosities . 161 3.5.5 Multi-Wavelength Counterparts . 162 3.6 Conclusions . 163 4 SPIRE dropouts 166 4.1 Introduction and Motivation . 166 4.2 Serendipitous Discovery of NGP6 D1........................ 170 4.3 Photometric Observations . 173 4.3.1 SMA . 173 4.3.2 NIKA . 177 4.3.3 VLA . 177 4.3.4 SDSS, UKIDSS and WISE . 178 4.4 Spectroscopic Observations . 180 4.4.1 RSR . 180 4.4.2 EMIR . 183 CONTENTS 13 4.4.3 NOEMA . 183 4.5 Photometric Analysis . 184 4.5.1 Template Fitting . 185 4.5.2 Fitting Modified Blackbodies . 188 4.5.3 The NIKA Observations . 196 4.5.4 The Statistics of Tdust=(1 + z).......................