Studying Dark Matter Using Weak Gravitational

Cover Page The handle http://hdl.handle.net/1887/58123 holds various files of this Leiden University dissertation Author: Brouwer, Margot Title: Studying dark matter using weak gravitational lensing : from galaxies to the cosmic web Date: 2017-12-20 Studying Dark Matter using Weak Gravitational Lensing From Galaxies to the Cosmic Web Proefschrift ter verkrijging van de graad van Doctor aan de Universiteit Leiden, op gezag van Rector Magnificus prof. mr. C.J.J.M. Stolker, volgens besluit van het College voor Promoties te verdedigen op 20 december 2017 klokke 12:30 uur door Margot M. Brouwer geboren te Amsterdam in 1989 Promotiecommissie Promotores: Prof. dr. Koen Kuijken (Universiteit Leiden) Prof. dr. Henk Hoekstra Overige leden: Prof. dr. Huub Röttgering Prof. dr. Joop Schaye Prof. dr. Catherine Heymans (University of Edinburgh) Prof. dr. Gianfranco Bertone (Universiteit van Amsterdam) ISBN: 978-94-6233-797-8 Copyright: Margot Brouwer, 2017 Dit proefschrift werd ondersteund door de Leidse Sterrewacht, de Leidse Faculteit voor Wis-en Natuurwetenschappen en de Leidse Universiteitsbibliotheek. “When a man sits with a pretty girl for an hour, it seems like a minute. But let him sit on a hot stove for a minute and it’s longer than any hour. That’s relativity.” – Albert Einstein “The greatest good is the knowledge of the union which the mind has with the whole nature.” – Baruch Spinoza To Jasper, my brand new husband, who did not only show me the true meaning of relativity, but also helped me discover that the heavens can be found both above and inside. iv Cover: Designed by Tineke Brouwer. The background represents the cosmic structure of galaxies. Based on research by Coutinho et al. (2016) a set of 24,000 galaxies is connected to its closest neigh- bours, enabling a visualization (created by Kim Albrecht) of the cosmic web (see http://cosmicweb.barabasilab.com). The looking glass on the back cover contains a Hubble Space Telescope com- posite image of dark matter (observed through weak gravitational lensing) in the galaxy cluster Cl 0024+17. Credit: NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University) CONTENTS v Contents 1 Introduction 1 1.1 Dark Matter ........................... 2 1.1.1 Discovery and evidence ................. 2 1.1.2 Cosmic structure ..................... 4 1.2 Weak gravitational lensing ................... 6 1.2.1 The weak lensing method ................ 6 1.2.2 The galaxy-galaxy lensing pipeline ........... 12 1.3 Outline .............................. 13 1.3.1 KiDS+GAMA: properties of galaxy groups ...... 13 1.3.2 Galaxy halo masses in cosmic environments ..... 15 1.3.3 A weak lensing study of troughs ............ 15 1.3.4 Lensing test of Verlinde’s emergent gravity ...... 16 2 KiDS+GAMA: properties of galaxy groups 19 2.1 Introduction ........................... 20 2.2 Statistical weak gravitational lensing .............. 23 2.3 DATA ............................... 25 2.3.1 Lenses: GAMA Groups ................. 28 2.3.2 Sources: KiDS galaxies ................. 29 2.3.3 Measurement of the stacked excess surface density profile ........................... 32 2.3.4 Statistical error estimate ................ 35 2.4 Halo model ............................ 37 2.4.1 Model specifics ...................... 41 2.5 Density profile of galaxy groups ................ 44 2.5.1 Matter density profiles of group-scale haloes ..... 45 2.6 Scaling relations ......................... 59 vi CONTENTS 2.6.1 The relation between halo mass and group r-band lu- minosity ......................... 59 2.6.2 The relation between halo mass and velocity dispersion 63 2.6.3 The relation between halo mass and r-band luminos- ity fraction of the BCG .................. 66 2.6.4 The relation between halo mass and group apparent richness .......................... 69 2.7 Conclusions ............................ 70 3 Galaxy halo mass in the cosmic web environment 77 3.1 Introduction ........................... 79 3.2 Galaxy-galaxy lensing analysis ................. 82 3.2.1 GAMA lens galaxies ................... 83 3.2.2 KiDS source galaxies .................. 84 3.3 Environment classification ................... 87 3.3.1 Cosmic environments .................. 87 3.3.2 Local density ....................... 90 3.3.3 Shuffled environments ................. 92 3.4 Analysis of the lensing profiles ................. 94 3.4.1 Contributions of group samples ............ 94 3.4.2 Surface density model .................. 96 3.5 Results .............................. 102 3.6 Discussion and conclusion ................... 105 4 Trough Lensing with KiDS, GAMA and MICE 109 4.1 Introduction ........................... 110 4.2 Data ................................ 113 4.2.1 KiDS source galaxies .................. 114 4.2.2 GAMA foreground galaxies ............... 116 4.2.3 KiDS foreground selection ............... 117 4.2.4 MICE mock galaxies ................... 118 4.3 Data analysis ........................... 120 4.3.1 Trough classification .................. 120 4.3.2 Lensing measurement .................. 123 4.4 Trough shear profiles ...................... 125 4.4.1 KiDS vs. GAMA troughs ................. 125 4.4.2 Lensing amplitudes ................... 129 4.4.3 Optimal trough weighting ................ 132 4.5 Redshift evolution ........................ 134 4.5.1 Redshift dependent trough selection .......... 136 CONTENTS vii 4.5.2 Excess surface density measurements ......... 139 4.5.3 Results .......................... 140 4.5.4 Predictions for higher redshifts ............. 143 4.6 Discussion and conclusion ................... 145 5 Lensing test of Verlinde’s Emergent Gravity 149 5.1 Introduction ........................... 151 5.2 GAMA lens galaxies ....................... 153 5.2.1 Isolated galaxy selection ................ 154 5.2.2 Baryonic mass distribution ............... 155 5.3 Lensing measurement ...................... 160 5.3.1 KiDS source galaxies .................. 161 5.4 Lensing signal prediction .................... 163 5.4.1 The apparent dark matter formula ........... 164 5.4.2 Point mass approximation ............... 166 5.4.3 Extended mass distribution ............... 167 5.5 Results .............................. 169 5.5.1 Model comparison .................... 171 5.6 Conclusion ............................ 175 6 Nederlandse samenvatting 181 6.1 Het donkere universum ..................... 182 6.2 Buigende ruimte-tijd ....................... 183 6.3 Dit proefschrift .......................... 185 Bibliography 189 Curriculum vitae 203 List of publications 207 Acknowledgements 211 1 1| Introduction “A cosmic mystery of immense proportions, once seemingly on the verge of solution, has deepened and left astronomers and astrophysicists more baffled than ever. The crux of the riddle is that the vast majority of the mass of the universe seems to be missing. Or, more accurately, it is invisible to the most powerful telescopes on earth or in the heavens, which simply cannot detect all the mass that ought to exist in even nearby galaxies.” – William J. Broad, New York Times (September 11, 1984). In these three sentences, New York Times reporter William Broad de- scribes what is still one of the biggest mysteries in modern cosmology. Over the past decades, astronomers have found evidence that all known types of matter - stars, planets, gas, dust and even exotic objects like black holes and neutrino’s - only constitute ∼ 20% of all mass in the universe. The other 80% is thought to consist of a hypothetical and invisible substance called dark matter. So far, however, all evidence is based exclusively on its gravitational interaction, either trough the dynamics of normal visible (often called ‘baryonic’) matter, or through the deflection of light in curved space- time. This latter approach, called gravitational lensing, is a unique way to probe the distribution of dark matter without making any assumptions on its dynamical state (such as virial equilibrium in clusters), and on scales larger than the extent of baryons (e.g. outside the visible disks of galaxies). With this thesis, I hope to increase our knowledge of the distribution and behaviour of dark matter using weak gravitational lensing. On scales ranging from individual galaxies to groups, and even to large-scale structure, I study the link between baryonic and dark matter with the ultimate goal of gleaning some insight into its possible nature. 2 Introduction 1.1 Dark Matter 1.1.1 Discovery and evidence The first evidence of Dark Matter (DM) was found by Zwicky (1933), who used the virial theorem to study dynamics of galaxies in the Coma cluster. He found that the mass density of the cluster must be at least 400 times larger than expected from its luminous contents, and suggested ‘Dunkle Materie’ as a possible cause. At this time, he used this term to indicate baryonic DM, such as cold non-radiating gas, planets or compact objects. His findings were substantiated by Kahn and Woltjer (1959) who studied the dynamics of the Local Group. More than 20 years later Rubin (1983), who studied the spectra of galactic optical disks and found their rotation curves flattened, brought DM to a wider attention. By that time Freeman (1970) had already found the flattening of rotation curves in the disks of spiral and S0 galaxies, and Bosma (1981) at scales far beyond the disks (using hydro- gen profiles). All their research combined showed that, on scales ranging from individual galaxies to clusters, the gravitational potential found by ap- plying Newtonian dynamics was too deep

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