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A Framework for Optimizing Exoplanet Targets for the James Webb Space

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A FRAMEWORK FOR OPTIMIZING EXOPLANET TARGETS FOR THE JAMES WEBB SPACE TELESCOPE f t * A thesis presented to the faculty of ^ San Francisco State University In partial fulfilment of t h y * The Requirements for The Degree Master of Science In Physics with a Concentration in Astronomy by Charles Daniel Fortenbach San Francisco, California December 2018 Copyright by Charles Daniel Fortenbach 2018 CERTIFICATION OF APPROVAL I certify that I have read A FRAMEWORK FOR OPTIMIZING EXO­ PLANET TARGETS FOR THE JAMES WEBB SPACE TELESCOPE by Charles Daniel Fortenbach and that in my opinion this work meets the criteria for approving a thesis submitted in partial fulfillment of the requirements for the degree: Master of Science in Physics with a Con­ centration in Astronomy at San Francisco State University. Associate Professor of Physics and Astronomy Dr. Jqspph Barranco Dept. Chair, Physics & Astronomy Associate Professor of Physics and Astronomy Dr. Courtney Dressing-£i—1 Assistant Professor of Astronomy University of California Berkeley A FRAMEWORK FOR OPTIMIZING EXOPLANET TARGETS FOR THE JAMES WEBB SPACE TELESCOPE Charles Daniel Fortenbach San Francisco State University 2018 The James Webb Space Telescope (JWST) will devote a significant amount of ob­ serving time to the study of exoplanets. It will not be serviceable as was the Hubble Space Telescope, and therefore the spacecraft/instruments will have a relatively lim­ ited life. It is important to get as much science as possible out of this limited observing time. We provide an analysis framework (including a suite of computer tools) that can be used to optimize the list of exoplanet targets for atmospheric char­ acterization. The tools take survey data from K2, TESS, or other sources; estimate planet masses as required; generate model spectra based on potential atmospheric characteristics; and then, given the capabilities of the various JWST instruments, determine an optimal target set. For a simulated survey data set of 1984 targets we categorize and rank the targets by observation time required to detect an atmo­ sphere. I certify that the Abstract is a correct representation of the content of this thesis. _______ Chair, Thesis Committee Date ACKNOWLEDGMENTS A number of people contributed to this Master’s thesis project. First, I would like to thank the faculty of the Physics and Math depart­ ments at the College of San Mateo, and in particular. Prof. Mohsen Janatpour, for helping to bring me back up to speed on undergraduate Physics and Math and for convincing me that I could still do school. I would like to thank my SFSU classmate, Josh Lamstein, for his time and patience giving me several LateX tutorials. I also would like to thank another classmate, Shervin Sahba, who pointed me to Oracle VirtualBox to run Linux on a Windows machine. I would like to thank Dirk Kessler, a super software engineer (co-founder of Gladly), for a key insight into running C code from python. I had been stuck on this problem for weeks and he solved it in about 5 minutes. I would like to thank my friends, Craig Schuler and Paul Seawell, two of the smartest people I know, for providing editorial advice. My sincere thanks to Prof. Eliza Kempton (Univ. of Maryland) the lead author of the Exo-Transmit code used to generate model spectra of planetary atmospheres. I had many questions and she had the answers. I would like to thank Dr. Tom Greene (NASA Ames), an expert on the JWST instrument suite, among other things, for his insight and guidance on a number of issues. He was generous with his time and patient with my many questions. I would also like to acknowledge the assistance of Dr. Natasha Batalha (currently a post-doc at UCSC) the lead author of the Pandexo code used to simulate JWST instrument performance. In order to develop a spectral detection algorithm it was important to gain an understanding of some of the intricacies of Pandexo. Her help on this was invaluable. I would like to thank Prof. Joseph Barranco for agreeing to be a mem­ ber of my thesis committee and for teaching me about many things in Astrophysics. I would also like to thank Prof. Andisheh Mahdavi for agreeing to be the chair of my thesis committee and for his explanations of Bayesian statistics, among other things. I would like to acknowledge Prof. Stephen Kane (now at UC Riverside) for his excellent introduction to the field of exoplanet research, and for helping me to connect with a primary thesis advisor. Last, but certainly not least, I would like to thank my thesis advisor, Prof. Courtney Dressing (UC Berkeley), for all of her help on this project. I was very fortunate that she decided to take me on in the midst of moving and beginning a new faculty position. I will be forever grateful for her encouragement and kind guidance along the way. vi TABLE OF CONTENTS 1 Introduction.............................................................................................................. 1 1.1 Background.................................................................................................... 2 1.2 Aim of this thesis .......................................................................................... 14 1.3 Other related w ork ....................................................................................... 14 2 Analysis framework and the JET C ode .................................................................. 28 2.1 Top level analysis framework and JET architecture ................................ 30 2.2 Generating model transmission spectra (ExoT_Master).......................... 32 2.2.1 Reading the survey d a t a ..............................................................34 2.2.2 Estimating planet masses ................................................................. 36 2.2.3 Deriving other planetary system p a ra m e te rs..........................37 2.2.4 Categorizing targets ...........................................................................42 2.2.5 Determining JWST observing constraints ....................................43 2.2.6 Generating model transmission spectra with Exo-Transmit . 48 2.3 Detecting transmission spectra with JWST (Pdxo_Master)....................51 2.3.1 Generating simulated transmission spectra with Pandexo . 55 2.3.2 Detecting the transmission s p e c t r a .......................................... 56 2.3.3 Determining the observing cycle time needed for detection . 65 2.4 Sorting and ranking targets (Rank-Master)................................................ 68 3 Validating the JET code ...........................................................................................71 vii 3.1 Planet masses.....................................................................................................72 3.2 System parameters, and transits observable............................................. 72 3.3 Model s p e c tra .....................................................................................................75 3.4 Simulated sp e c tra ................................................................................... 76 4 Program installation ....................................................................................... 82 4.1 Hardware configuration......................................................................... 82 4.2 Software co n figuration...................................... 84 5 Results/Discussion...................................... 90 5.1 Baseline (full su rv e y )......................................................................... 90 5.2 Noise floor variation ...................................................... 96 5.3 Atmospheric equation of state variation....................................................... 98 5.4 Detection threshold variation ...................................................... 100 5.5 Instrument variation ......................................................................................102 6 Conclusions/Future Work ......................................................................................107 6.1 Conclusions......................... 107 6.2 Opportunities for further stu d y ..................... 110 Appendix A: JET Code .................................................................................112 Appendix B: Baseline JET R u n ................................................................................... 165 viii References LIST OF TABLES Table Page 1.1 JWST Key Facts and Figures..................................................................... 3 1.2 NIRSpec Disperser/Filter Combinations .......................................... 7 2.1 Excerpt from Catalog of Simulated TESS Detections ......... 35 2.2 Observation Time E le m e n ts................................................. 67 3.1 Basic Survey Data for V a lid a tio n .................... 73 3.2 Validation of JET Calculation of Planetary Parameters..............................74 4.1 Computer Hardware for Development and Testing...................... 83 4.2 General Software Installation List for J E T .................................................. 88 4.3 Python Packages/Modules for JET Installation ........... 89 5.1 JET Baseline run - Input Parameters............................................................91 5.2 Baseline Run Statistics 1 ................................. 94 5.3 Baseline Run Statistics 2 ....................... 95 5.4 Effect of Instrument Choice on Detection (Sullivan Target 1292) . 106 x LIST OF FIGURES Figure Page 1.1 The Observatory from various aspects............................................
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