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The Age of the Milky Way Galaxy from White Dwarf Chronometry

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THE AGE OF THE MILKY WAY GALAXY FROM WHITE DWARF CHRONOMETRY APPROVED BY DISSERTATION COMMITTEE: R. Edward Nather, Supervisor Donald E. Winget Edward L. Robinson William H. Jefferys Jim Liebert Copyright by Charles F. Claver, B.A. 1995 Dedication To my family; Jack, Paulette, and Jeanne in memory of Chet, Harlan, Maria, and Steve. THE AGE OF THE MILKY WAY GALAXY FROM WHITE DWARF CHRONOMETRY by CHARLES FREDERICK CLAVER, B.A. DISSERTATION Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY THE UNIVERSITY OF TEXAS AT AUSTIN May, 1994 Acknowledgements When I left California to come to Texas I knew I wanted to pursue astronomy, but I had no idea I was taking the first step to the most chalenging and interesting phase of my life to date. The first astronomer I met was Ed Nather. I described to him my telescope making hobby and interests and by the time we were through, without ever having seen me before, Ed gave me a place in his lab to continue my work. From this moment on Ed became my mentor. Ed always gave me a great deal of freedom, but also seemed to know when it was necessary to step in and help, discipline, or correct me. I cannot express enough how grateful I am to Ed for allowing me to do what I love most – astronomy. Thank you Ed, for your faith in me, and for giving me the opportunity and guidance that helped me fulfill a lifelong dream. Equally inspiring to me was Don Winget. I first met Don at McDonald Observatory while I was working on my senior thesis project in 1986. I asked Don what he did. He proceeded to give me very excitedly a synopsis of the white dwarf field. I asked him what was the most important problem in the study of white dwarfs. Don replied "numbers". With that simple response, Don is directly responsible for igniting the fire of curiosity in me which led to my total commitment to professional astronomy. Without Don's continued support and v help to keep this fire alive I would never had made it through graduate school. Thank you, Don. The "Lab" environment that Ed and Don cultivate is second to none. It may seem hopelessly chaotic at times, but in reality it is vibrantly alive with science, philosophy, and life. Of the truly unique friends and collaborations to emerge from this environment are truly unique I have been blessed by many. In particular, I am grateful to have met my professional "big brother", Matt Wood and through him his wife Clara. Matt is someone I admire, looked up to, and can always rely on for straight answers. Other good friends from the lab include Butler Hine, Chris Clemens, Scot Kleinman, Judi Provecal, Paul Bradley, Atsuko Nitta, Mike Montgomery, Usama Aziz, and Todd Watson. I could not have asked for a better family than the one I have. All throughout my life they have supported my interests, encouraged me to learn new things, and have always been willing to help in anyway they could. Most parents would not have driven their son 60 miles every Friday night for 5 years (until I learned to drive) to the Telescope Makers Workshop at Chabot Observatory so that I could rub two pieces of glass together with sand in between. Thank you Mom and Dad for your love, patience, understanding, and most of all for your confidence and trust in me. Jeanne, my sister, you are one of my best friends. Our many conversations have been and continue to be a very important part of my life. Thanks for listening. I am also blessed with another family, my chosen one, who have been equally supportive in ways parents and siblings cannot. These are the people I grew up with, and are collectively known as "The Newton Way Gang" – after the vi street we lived on. Over the years this chosen family has grown as we each meet new people and include them in our lives. Even though we are spread accross the country, the love that is shared among us only continues to strengthen. So to you: Mike Cadigan, Terry and Lynne Shapliegh, Larry Cadigan. Rob and Jamie Loud, Greg Sosa, Mo and Lisa, Dan and Vickie, and Chris Klinger I am truly thankful to know you. It is part of life that sometimes we lose a member of the family. This dissertation is, in part, dedicated to one who I knew so briefly, but showed me how to savor the special moments life has to offer. Steve, wherever you might be – Haaayyyyy! While attending the University of Texas I have also met some truly exceptional people who have helped me along the way towards my degree. I first met Dean Hines on the last day of orientation for the new incoming graduate class. Having spent the past three years at Texas as an undergraduate, I didn't feel like I needed to be oriented. This did nothing to dispel wild rumors of who this Claver guy was, which came to an abrupt halt when Dean and I showed up that day in full Grateful Dead attire. We've been dear friends ever since; thanks Dean. Later that year I met Mark Cornell, and more recently his new wife Debbie. Mark has taught me a sharpness of thinking I would never have developed otherwise. In addition to this, Mark and Debbie are just genuine good people to know - thanks you two! I cannot really explain how it was that Phillip MacQueen and I became friends and collaborators. I can only say that without Phillip the Prime Focus Camera would never have happened – it is as much his instrument as it is mine. Working with Phillip has been, and continues to be, an education and an vii inspiration, and just plain fun. Thanks Phillip, for your herculean efforts over the years., and my appologies to your wife if I've kept you out too late :). I am truly indebted to you. Someone who will always hold a special place in my heart is A–Lan Reynolds, who I met during her second Masters program at the University of Texas. We seem to be cut from the same piece of cloth, albeit opposite ends. A–Lan, you were a brilliant shining light during my darkest years as a graduate student. Even now, as things seem much brighter to me, your light is blinding and your warmth unending. Miao. Op. Po. To Luke and Sherri – ogidy ogidy ogidy. Thank you for the wonderful T– shirt, but most of all thanks for all the wonderful outdoor experiences we've shared. May there be may many more to come. Thanks to Gary Hansen for all the instructive and enlightening conversations over the years, and for including me in your outdoor experiences with Chris and your newest family member, Carli. I would also like to express my sincerest thanks to Frank Bash, Tom Barnes, and the entire staff of McDonald Observatory for their support during the construction of the Prime Focus Camera. At Mt. Locke, I am especially grateful to Dave Doss, Ed Barker and Mark Adams, Jerry Martin, Ed Dutchover, and George Grub (and his crew) for their help and support over the years. I owe special thanks to Jimmy Welborn and George Barzcark for welcoming me into their work place and sharing their knowledge of machining while I built the Prime Focus Camera. viii To David Way and his family, thanks for your support both in the department and away. Our trips to the lake listening to SRV while the sun set on a warm Summer's night went a long way towards easing the strain of graduate school. Finally, but not in the least, I am forever indebted to Beth Clark. If it weren't for Beth this dissertation would not have been completed with my sanity intact. Everyday she does something seemingly small that makes a very big difference in my life. I love you, Beth with all my heart, thanks for everything – big and small. ix THE AGE OF THE MILKY WAY GALAXY FROM WHITE DWARF CHRONOMETRY Publication No._____________ Charles Frederick Claver, Ph. D. The University of Texas at Austin, 1995 Supervisor: R. Edward Nather The age of our own Galaxy – the Milky Way – is one of the principal pieces of information we have to constrain our understanding of how the Universe evolved to its current state. With the assumption that our Galaxy is no different than any other of its type and that our locale in the Universe in not unique, the age of the Milky Way places constraints on how much time has elapsed since galaxies and the Universe were first formed. Estimates for the Galaxy's age have ranged from 10 to 20 billion years, but this age spread is too large to constrain the models we have describing the evolution of the Universe. Perhaps the most accurate way we have of estimating ages comes from the white dwarf stars – the cooling x remnants of stellar evolution. The difficulty is that there are too few white dwarfs known for us to fully exploit them as the accurate chronometers they are. In the first part of this work I present new instrumentation and photometric techniques designed specifically to search for and identify the oldest white dwarf stars. In collaboration with Phillip MacQueen I have converted the 0.76m Boller and Chivens telescope at McDonald Observatory into a highly sensitive digital f 3 Prime Focus Camera.
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