THE ATACAMA COSMOLOGY TELESCOPE: THE UNIVERSE AT 148 & 218 GIGAHERTZ Danica W. Marsden A DISSERTATION in Physics and Astronomy Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy 2011 Mark Devlin, Professor, Physics & Astronomy Dissertation Supervisor Charlie Johnson, Professor, Physics & Astronomy Graduate Group Chairperson Dissertation Committee: Gary Bernstein, Professor, Physics & Astronomy Bhuvnesh Jain, Professor, Physics & Astronomy Burt Ovrut, Professor, Physics & Astronomy Masao Sako, Professor, Physics & Astronomy Acknowledgements I would like to thank my advisor, Mark Devlin, without whom this thesis would not exist. He not only worked to provide a convivial atmosphere within the group, he created a family of sorts. I am grateful for the opportunity I had to learn while working in his laboratory and while in the field, from Mark as well as Jeff Klein, Harold Borders, Robert Thornton, Simon Dicker, Daniel Swetz, and Madhuri Kaul. Erik Reese, Kim Scott, Phil Korngut, Tony Mroczkowski, and Matthew Truch always made themselves available for illuminating discussions. I have truly grown as an experimental cosmologist as a result of the opportu- nity to be involved in and work with the scientists of the ACT collaboration. In particular: Mark Halpern, Lyman Page, Suzanne Staggs, Joseph Fowler, Michael Niemack, Tobias Marriage, Adam Hincks, Eric Switzer, Jon Sievers, Matthew Has- selfield, Sudeep Das, Mike Nolta, David Spergel, Neelima Sehgal and Jo Dunkley. Mark Halpern directly influenced my life path, and without his invitation to work in his laboratory as an undergraduate student I would very likely not be an experimental cosmologist today. Tobias Marriage became in many respects my defacto advisor during the analysis portion of my thesis work; his tireless efforts and friendship also made this body of work possible. Marcella Massardi, Bruce Partridge and the staff of the Australian Telescope Compact Array (ATCA) were invaluable to my collection and analysis of ATCA data. I thank the University of Pennsylvania and the Physics & Astronomy Depart- ment for enabling my work and studies, and for providing a rich academic envi- ronment in which to do them. I would also like to acknowledge the international science agencies whose foresight led to the funding of the ACT project. Lastly, I thank my family and friends. They never fail to reiterate that one can do anything one puts one’s mind to. ii ABSTRACT THE ATACAMA COSMOLOGY TELESCOPE: THE UNIVERSE AT 148 & 218 GIGAHERTZ Danica W. Marsden Mark Devlin The Atacama Cosmology Telescope (ACT), located in the Atacama Desert of Chile at an elevation of 5,190 m, represents a decade of work by a collabora- tion spanning multiple continents. ACT was designed to observe with arcminute angular resolution and a degree-sized field of view, resulting in an observed tem- perature anisotropy power spectrum that spans angular harmonic multipole 500 < l < 10,000 on the sky. This range spans the linear perturbation regime of the primary Cosmic Microwave Background (CMB) anisotropies into the secondary anisotropies created by nonlinear physical processes at later times. Low multipole coverage allows for cross-calibration with all-sky experiments such as the Wilkin- son Microwave Anisotropy Probe (WMAP) and Planck, and high multipoles probe structures such as clusters of galaxies through the thermal Sunyaev-Zel’dovich effect (tSZE), and extragalactic point source populations. Millimeter wavelength- selected point sources, most of which are high-redshift galaxies, have only recently been systematically studied. The fidelity of CMB maps and galaxy cluster cat- alogs depend on understanding the galaxy populations, globally as well as on a local astrophysical level where they impact the ability to generate reliable mass- observable relations for galaxy clusters, which are important for cluster-derived iii cosmology. The multifrequency nature of ACT data permits the characterization of multiple galaxy populations through their spectral energy distributions (SEDs) in a relatively unexplored frequency regime. Analysis of ACT-selected galaxies informs the current understanding of the evolution of structure formation over cosmic time. This thesis begins by motivating the ACT science. A description of the ACT telescope and camera, with focus on the bandpass determination for the three optics tubes of the camera is followed by a synopsis of the observations to date. The map-making strategies used to produce the data analyzed for this thesis are reviewed, to provide background for the source analysis derived from ACT maps. ACT-detected source populations are analyzed in detail, including data taken during follow-up observations on the Australian Telescope Compact Array (ATCA) at 20 GHz. iv Contents Abstract iii List of Tables viii List of Figures ix 1 Introduction 1 1.1 An Expanding Universe . 1 1.2 The Cosmic Microwave Background . 2 1.2.1 Primary Anisotropies . 3 1.2.2 Secondary Anisotropies . 6 1.2.3 The Sunyaev-Zel’dovich Effect . 7 1.3 The Multifrequency ΛCDM Universe . 12 1.3.1 An Accelerating Universe . 12 1.3.2 Inflation . 13 1.3.3 Cosmological Paradigm . 14 1.3.4 Remaining Questions . 16 1.4 Millimeter-Wavelength Galaxies . 18 1.4.1 Spectral Energy Distributions . 20 1.4.2 Radio Galaxies . 21 1.4.3 Dusty Star-Forming Galaxies . 24 1.5 The Atacama Cosmology Telescope . 30 1.6 Overview . 31 2 The Atacama Cosmology Telescope 32 2.1 Site Location . 33 2.1.1 Atmospheric Opacity . 33 2.1.2 Logistics . 36 2.2 Telescope Structure and Warm Optics . 37 2.2.1 Motion Control Systems . 37 2.2.2 The Receiver Cabin . 38 2.2.3 Warm Optics . 39 2.3 MBAC . 43 2.3.1 Cryogenics . 44 2.3.2 Cryogenic Control System . 46 2.3.3 Mechanical Construction . 50 v 2.3.4 Cold Optics: ACT Lenses and Filters . 52 2.3.5 Beams . 62 2.4 The ACT Detectors . 65 2.4.1 Detector Parameters . 67 2.4.2 Cold Readout Electronics . 70 2.4.3 Warm Readout Electronics . 73 2.4.4 Optical Time Constants . 74 2.4.5 Detector Array Pointing . 77 3 ACT Observations, Scan Strategy and Map-making 79 3.1 Observations . 80 3.2 Scan Strategy . 82 3.3 ACT Data . 83 3.3.1 Data Management . 83 3.3.2 Data Selection . 84 3.3.3 Calibration . 87 3.3.4 Pointing . 89 3.4 The ACT 2008 Maps . 89 3.4.1 Preprocessing . 90 3.4.2 Map-making . 91 4 ACT Power Spectrum and SZE Galaxy Cluster Results 94 4.1 The ACT Power Spectrum . 94 4.1.1 Cosmological Constraints . 98 4.2 ACT Galaxy Clusters . 99 4.2.1 The Catalog . 101 4.2.2 Optical and X-ray Follow-up of Clusters . 102 4.2.3 Cosmology From a Complete High-Mass Sample . 106 4.2.4 Map-stacking at the Locations of LRGs . 108 5 ACT-selected Galaxies 110 5.1 ACT Source Catalogs . 111 5.1.1 Source Extraction . 112 5.1.2 The Catalog . 120 5.1.3 Astrometric Accuracy . 122 5.1.4 Flux Density Recovery . 123 5.1.5 Purity and Completeness . 132 5.2 The ACT-selected Source Population Characteristics . 134 5.2.1 Comparison With Other Source Catalogs . 134 5.2.2 Correlation With Galaxy Clusters . 140 5.2.3 Source Number Counts . 141 5.2.4 Contribution to the Power Spectrum . 143 5.2.5 The Undetected Source Background . 144 5.2.6 Spectral Indices . 145 5.3 Follow-up Observations with the Australian Telescope Compact Ar- ray................................... 149 5.3.1 Observations . 149 vi 5.3.2 Analysis . 151 5.3.3 Results . 154 6 Conclusion 156 6.1 Conclusion . 156 6.2 Ongoing Study . 157 6.2.1 ALMA Follow-up Observations . 158 6.2.2 Other Follow-up Observations . 161 6.3 ACTpol: The Future of ACT . 161 A The ACT Source Catalog 162 Bibliography 171 vii List of Tables 1.1 ΛCDM Fundamental and Derived Parameters . 17 2.1 Telescope and optics parameters . 43 2.2 Filter location and cut-off frequency in MBAC . 57 2.3 Calculated properties of the MBAC filters . 63 2.4 Summary of Beam Parameters from the 2008 Observing Season . 65 2.5 The ACT detector parameters. 69 5.1 Pointing Accuracy . 123 5.2 Number Counts, Purity, and Completeness for the ACT Source Catalog. 133 A.1 The ACT high significance 148 and 218 GHz extragalactic source catalog. 163 viii List of Figures 1.1 The Wilkinson Microwave Anisotropy Probe (WMAP) measure- ment of the CMB anisotropies. 4 1.2 The WMAP 7-year temperature power spectrum with data from ACBAR and QUaD experiments. 5 1.3 The SZE effect. 9 1.4 The SZE for galaxy cluster Abell 2163. 10 1.5 Constituents of the Universe . 16 1.6 Cosmic timeline . 18 1.7 Spectral energy distribution for Pictor A and example image of an AGN. ................................. 23 1.8 Spectral energy distribution and composite image of M82. 25 1.9 Extragalactic background light. 27 2.1 Effective atmospheric temperature as a function of PWV. 35 2.2 Atmospheric Opacity at the ACT site with ACT frequency bands shown. 36 2.3 The Chajnantor plateau in the Atacama desert of northern Chile. 37 2.4 The Atacama Telescope. 40 2.5 Ray trace of the off-axis Gregorian optics and MBAC mounted in the receiver cabin of the telescope . 41 2.6 Primary and secondary mirror panels surface alignment deviations. 42 2.7 A cut-away of the MBAC cryostat. 45 2.8 A schematic of thermal regulation and connections in MBAC. 46 2.9 Refrigeration cycling illustrated. 49 2.10 The MBAC cold reimaging optics. 53 2.11 A cross-section of the 148 GHz optics tube.