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Externally Dispersed Interferometry for Terrestrial Exoplanet Detection

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Externally Dispersed Interferometry for Terrestrial Exoplanet Detection EXTERNALLY DISPERSED INTERFEROMETRY FOR TERRESTRIAL EXOPLANET DETECTION ADissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Philip Steven Muirhead August 2011 !c 2011 Philip Steven Muirhead ALL RIGHTS RESERVED EXTERNALLY DISPERSED INTERFEROMETRY FOR TERRESTRIAL EXOPLANET DETECTION Philip Steven Muirhead, Ph.D. Cornell University 2011 Terrestrial exoplanets are observationally challenging todetectandcharac- terize. Compared to gas giant exoplanets, terrestrial exoplanets introduce sig- nificantly smaller radial velocity signals and transit depths on their host stars. The signals are larger for terrestrial exoplanets orbiting M-dwarf stars, which have lower masses and radii than Sun-like F, G and K-type stars, and domi- nate stellar populations by number. Detecting exoplanets around M dwarfs is itself difficult because of their lower luminosities and lower flux at visible wave- lengths, where most radial velocity and transit exoplanet surveys operate. Ipresentherethemotivation,developmentandresultsfromaradialveloc- ity program conducted on M dwarfs using near-infrared wavelengths, where M dwarf spectra peak in flux. To achieve high radial-velocity precision, I have used atechniquecalledexternallydispersedinterferometry.Itinvolvesthecombina- tion of an interferometer and a moderate-resolution spectrograph on the 200 inch (5.1 m) Hale Telescope at Palomar Observatory. The TripleSpec Exoplanet Discovery Instrument, or TEDI, is the first such instrument tooperateatnear- infrared wavelengths. Our results indicate that contamination by narrow absorption lines intro- duced by the Earth’s atmosphere limit radial velocity performance to that which can detect gas giant planets. I have conducted a survey of nearby M dwarfs, and can rule out with 3σ confidence the presence of short-period gas giant planets in circular orbits around a few nearby M dwarfs. The results of this experiment di- rect future extrasolar planet instrumentation toward spectral regions with little telluric contamination and with higher resolution, to detect terrestrial exoplan- ets orbiting M dwarfs. BIOGRAPHICAL SKETCH IwasbornonJanuary14th,1983,inMorristown,NewJersey,the second child of Susan Putnam Muirhead and E. Eric Muirhead, Jr. In August, 1983, when I was seven months old, my family moved to Los Angeles where my fa- ther had a teaching position at Chadwick School, a private K-12 school in Palos Verdes Peninsula. I lived in San Pedro until August, 1984, when my family moved to the Chadwick School campus. I attended pre-school atBroadacres from 1986 to 1988, and attended kindergarden, first and secondgradeatChad- wick. In June of 1989 my family moved to nearby Redondo Beach. In June of 1991, when I was 8 years old, my family moved to a suburb of Houston, Texas. IlivedintheOldeOaksneighborhoodinnorthwestHarrisCountry, and at- tended Oak Creek Elementary, Wells Middle School and Westfield High School from 1991 to 2001. Notable accomplishments include performing trombone in the Westfield High School Band, which won the Texas State Marching Cham- pionship in 1998 with a marching rendition of Leonard Bernstein’s Mass,and won the Texas Music Educators Association Honor Band competition with a performance of Paul Hindemith’s Symphony in B-flat in 1999. I do not recall be- ing particularly interested in physics or astronomy before college; however, I was excited by calculus and statistics which I attribute to having a particularly engaging mathematics teacher, Mr. E. C. Hedstrom. In 2001, I left Texas to begin undergraduate studies at the University of Michigan in Ann Arbor. I was enrolled in both the Residential College and the Honors Program within the College of Literature, Science andtheArts.Iwasa member of the Michigan Marching Band for two years, attendingthe2006Cit- rus Bowl and 2007 Capital One Outback Bowl. I became interested in physics during my first year, and took my first astronomy course during my second iii year. By the end of my second year I had declared a double major in Astron- omy and Astrophysics and General Physics.Duringmythirdandfourthyearsin college I worked with Professor John Monnier, assisting withtheassemblyand software design for the Michigan Infrared Combiner, a beam combiner at the CHARA array at Mt. Wilson Observatory capable of imaging the surfaces of main sequence stars at infrared wavelengths (Monnier et al.,2007).Theexperi- ence was extremely fun and rewarding, and it convinced me to apply to Ph.D. programs in astronomy. In 2005, I graduated from Michigan with a Bachelors of Scienceandmoved to Ithaca, New York, to begin a Ph.D program in Astronomy and Space Sci- ences at Cornell University. I began research with my advisor, James Lloyd, in Spring of 2006. Since then, my Cornell and Ithaca experienceshavebeendeeply rewarding. In 2007 I received a NASA Earth and Space Sciences Graduate Fel- lowship, supporting my dissertation research for 3 years. In2009Ireceivedthe Cranson W. and Edna B. Shelley Award for Graduate Research in Astronomy. In 2010 I received a Z. Carter Patten ’25 Graduate Fellowship,andaNewYork Space Grant Graduate Fellowship. I publicly defended my dissertation in May of 2011. iv For my parents, Eric and Susan, and my brother, Elliot v ACKNOWLEDGEMENTS First and foremost, I would like to thank my advisor at Cornell, James Lloyd, for offering me a leading role in the development and implementation of TEDI for my dissertation research. I greatly appreciate the independence and respon- sibility James has given me, but also the insight he provided when the project was especially challenging. I would like to thank my primary collaborator, Jerry Edelstein at Berkeley’s Space Sciences Laboratory, who has acted as a second advisor and was my host while in residence at Berkeley in the Spring of 2010. Jerry’s energy and enthusiasm for designing and implementing astronomical in- struments is simply inspirational. I would like to thank Chuck Henderson, who as the chief mechanical engineer for the TripleSpec Spectrograph acted as yet a third advisor and gave me the opportunity to contribute to thespectrograph’s design, construction and deployment at Palomar Observatory. IwouldliketothankthemembersofmySpecialCommittee–James Lloyd (Chair), Terry Herter, Richard Lovelace, James Cordes and Steven Squyres–for their valuable advice during my Q, A and B Exams, and for their feedback and comments on this dissertation. I would like to thank Jason Wright and Kevin Covey for their guidance and mentorship as postdocs in my research group. I would like to thank the whole infrared group at Cornell, whoseadviseandsup- port was extremely useful for my project at various times. In particular I would like to thank Terry Herter, Gordon Stacey, Jim Houck, StephenParshley,Joe Adams, George Gull, Thomas Nikola, Greg Sloan and, last but not least, Laurie McCall. I would also like to thank David Erskine of the Lawrence Livermore National Laboratory, who pioneered the EDI technique, and has been an enthu- siastic and fun collaborator to work with. I would like to thank Travis Barman and Henry Roe for providing the stellar and telluric models (respectively) used vi in the simulations in this dissertation. IwouldliketothankmyclassmatesatCornell.Iamamazedbyhow suc- cessful the Astronomy Graduate Network (AGN) has become, andtheimpor- tant role it has in the department. I specifically want to thankmyofficemates, Barbara Rojas-Ayala and Carl Ferkinhoff, for the many thoughtful discussions. IwouldliketothankPhillipAndelson,DavidKimberandKatherine Ham- ren, who while undergraduates assisted substantially in there-deploymentof TEDI. I would also like to thank my friends in Ithaca who made mystayhereso much fun, especially the Ranch-Lakehouse Corridor: Ryan Shannon, Matthew Warkentin, John Gregoire, Sharon Gerbode, Laura Spitler, Briony Horgan and Richard Kipphorn. This work has been supported by the National Science Foundation un- der Grant No. AST-0505366, AST-096064, AST-0905932, AST-0504874 and by NASA Grant NNX09AB38G. This work was also supported by NASA Head- quarters under the NASA Earth and Space Science Fellowship Program - Grant NNX07AP56H. IwouldliketothankthemembersofConceptualDesignStudyTeam for the Gemini Exoplanet Discovery Instrument (GEDI)–led by James Lloyd and including Jerry Edelstein, David Erskine, Terry Herter, Stephen Parshley, Neil Reid, David Charbonneau, Travis Barman, and Anna Moore–and the concep- tual design reviewers–Tom Greene, Tom McMahon, Gordon Walker and Peter Conroy–for their important feedback. The GEDI Design Study was extremely useful and influential for the TEDI project. The GEDI Design Study was com- missioned as one of the competing Precision Radial Velocity Spectrometer de- signs and funded by the Association of Universities for Research in Astronomy, Inc., (AURA) under contract 0084699-GEM00442. The Gemini Observatory is vii operated by AURA under a cooperative agreement with the NSF onbehalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), Comisi´on Nacional de Investigaci´on Cient´ıfica y Tecnol´ogica (Chile), the Australian Research Council (Australia), Minist´erio da Ciˆencia e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnolog´ıa e Inno- vaci´on Productiva (Argentina). Parts of Chapters 1, 2, 3, 4, 5, 6 and 8 appear in the June, 2011 issue of Pub- lications of The Astronomical
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