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Detection and Characterization of Extrasolar Planets Through Planet-Disk Dynamical Interactions

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Detection and Characterization of Extrasolar Planets Through Planet-Disk Dynamical Interactions Western University Scholarship@Western Electronic Thesis and Dissertation Repository 4-19-2017 12:00 AM Detection and Characterization of Extrasolar Planets through Planet-Disk Dynamical Interactions Maryam Tabeshian The University of Western Ontario Supervisor Prof. Paul A. Wiegert The University of Western Ontario Graduate Program in Astronomy A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Maryam Tabeshian 2017 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Other Astrophysics and Astronomy Commons Recommended Citation Tabeshian, Maryam, "Detection and Characterization of Extrasolar Planets through Planet-Disk Dynamical Interactions" (2017). Electronic Thesis and Dissertation Repository. 4503. https://ir.lib.uwo.ca/etd/4503 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Structures observed in circumstellar disks may be caused by gravitational interaction with planetary or stellar companions. These perturbed disks are often signposts of planet birth in exoplanetary systems, and offer insights into the properties of both the disk and the perturbing planets. Therefore, structures observed in these disks provide a powerful tool for detecting and studying extrasolar planetary systems. In this work, we examine the link between disk structures and nearby/embedded planets using numerical simulations of both hypothetical and observed disk systems. We demonstrate that gaps can be opened in dynamically cold debris disks at the mean- motion resonances (MMRs) of an orbiting planet. These gaps are opened away from the orbit of the planet itself, revealing that not all disk gaps need contain a planetary body. These gaps are large and deep enough to be detectable in resolved disk images for a wide range of reasonable disk-planet parameters. The gap location, shape, and size are diagnostic of the planet location, eccentricity and mass, and allow one to infer the existence of unseen planets, as well as calculate many important parameters of both seen and unseen planets in these systems. We suggest that the widths, locations, and shapes of the two most prominent resonances, the 2:1 and 3:1 MMRs, could be used to determine: 1) the position of any unseen planets for more efficient targeted searches, and 2) the mass, semimajor axis and eccentricity of the planetary perturber, and present an algorithm for doing so. We apply our dynamical model of planet-disk interactions to the protoplanetary disk around the young pre-main sequence star HL Tauri which was observed recently in unprecedented detail by the Atacama Large Millimeter/submillimeter Array (ALMA). We determine that the disk structures that are likely sculpted by yet-to-be detected planets embedded in this gas-rich disk can be reproduced to a large extent using a simple particle-only model. For example, the number of planets in the HL Tau system remains a matter of debate; however, our results show that at least 5 of the observed gaps could be produced with only 3 planets in the system, where the additional gaps are due to mean-motion resonances. Our fitting of planetary masses and distances are also consistent with those in the literature. Therefore, we conclude that a particle-only treatment of gas-rich disks may be useful in understanding disk-planet dynamical interactions in some cases, and provide ‘low-cost’ initial parameter determinations which can ultimately be used as a starting point for investigating protoplanetary disks more thoroughly using computationally expensive hydrodynamic models. In the present study, we show that numerical simulations of circumstellar disks provide a powerful tool for the study of planets and planetary systems which can ultimately help in understanding their formation and evolution. Keywords: celestial mechanics - circumstellar disks - planets and satellites: detection - planets and satellites: fundamental parameters - planetdisk interactions - protoplanetary disks: individual (HL Tau) i Co-Authorship Statement This thesis dissertation contains adaptations from three papers that are either published in a peer-reviewed journal or soon will be. These include: - Chapter 2: Detection and Characterization of Extrasolar Planets through Mean-Motion Resonances. I. Simulations of Hypothetical Debris Disks, published in the Astrophysical Jour- nal (Tabeshian, M. & Wiegert, P. A., 2016, ApJ, 818, 159); - Chapter 3: Detection and Characterization of Extrasolar Planets through Mean-Motion Resonances. II. The Effect of the Planet’s Orbital Eccentricity on Debris Disk Structures, sub- mitted for publication in the Astrophysical Journal (Tabeshian, M. & Wiegert, P. A., 2017, ApJ (submitted)); - Chapter 4: Detection and Characterization of Extrasolar Planets: Applying a Particle- only Model to the HL Tau Disk, to be submitted for publication. Contributions to these papers were made by myself as well as by my PhD supervisor, Dr. Paul Wiegert. The simulation codes using a numerical integrator based on the Wisdom-Holman algorithm were written by Dr. Wiegert in C. I ran the code and processed and analyzed the output using a code I wrote in Interactive Data Language (IDL). I then prepared the figures as well as the manuscripts while Dr. Wiegert provided guidance and suggestions on a regular basis. I also wrote a code in IDL which called the simulation code and implemented chi- squared minimization as well as Monte Carlo simulations and uncertainty calculations for the project described in Chapter 4. ii Acknowledgements To my family: Since the day I set foot on this planet, I have been blessed with the most incredible family in the world! A mom and dad that have always gone above and beyond for my sister and I to make our dreams come true. Thank you both for raising me up to more than I could ever be and for every sacrifice you made for me to be where I am now. And of course a big thanks to an amazing big sister who has always been by my side, helping me reach for the stars. But how can I ever thank the three of you enough for having my back and for always being there for me, so lovingly, so unconditionally? Without your unwavering support, I could not have gone through the amazing journey that started with a decision a 9 year-old girl made, that one day she would become an astronomer! That journey is not coming to an end with a PhD degree in astronomy; this is just the beginning of a new chapter, and I am truly blessed to have all of you in this with me ... To my friends: I consider myself very lucky to have always been surrounded by an amazing support group of friends, some of whom I have long considered family. It is impossible to name all of you here and I only hope that I have been able to tell you how much every single one of you has given meaning to my life. To my teachers: Perhaps I need to go back, far back, to the person who first taught me how to read, and thank every single teacher I have had ever since for building the foundations of my humble knowledge. But I would like to especially thank Drs. Stan Metchev and Peter Brown at the University of Western Ontario (UWO) for sharing with me their vast knowledge of planets and planetary systems, as well as Drs. Neil Basescu, with whom I took my first ever astronomy course, and Bert Liberi at the State University of New York, Westchester Community College for their undeniable role in developing my knowledge in physics and in mathematics. Also, my sincere thanks to Dr. Jan Cami at UWO for his help and patience with my programming questions and the dilemmas I so often ran into with my code! And many thanks to Dr. Jamshid Ghanbari, a dear family friend and astronomy professor that my father took me to when I was very young and someone who played a great role in my growing interest in astronomy. Thank you all! To my MSc. supervisor, Dr. Martin Houde: When it comes to telling you how grateful I am for what you did for me, I always find myself at a loss for words. It has always been so heartwarming to know that you remained genuinely caring of my progress and wanted what was best for me that makes me incredibly grateful for having had you as my supervisor. Even though I will never be able to say this enough, but thank you for supporting me and my decision at a time that I needed it most. Your support led me to the path for success and gave me so much more that I can’t even begin to describe. iii And finally, to my PhD supervisor, Dr. Paul Wiegert: I wish I knew where to begin and how to tell you how much a decision you made not even three years ago changed the course of things for me. Thank you for giving me the chance, the honor, the privilege of being your student, which I never took for granted. There are absolutely no words that would do justice in expressing the extent of my gratitude to you for all that you have done for me over the years and for the wealth of knowledge that you generously provided me with. Your support, your encouragement and the faith you have had in me are priceless and I will forever be indebted to you. iv Dedication To my parents, for their never-ending love and support ... v Contents Abstract i Co-Authorship Statement ii Acknowledgements iii Dedication v List of Figures ix List of Tables xiii List of Appendices xiv 1 Prelude 1 1.1 Introduction .
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