TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER SPACE TELESCOPE INFRARED SPECTROGRAPH A Dissertation 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 Shannon Laura Gutenkunst May 2008 (cid:176)c 2008 Shannon Laura Gutenkunst ALL RIGHTS RESERVED TRACING ABUNDANCES IN GALAXIES WITH THE SPITZER SPACE TELESCOPE INFRARED SPECTROGRAPH Shannon Laura Gutenkunst, Ph.D. Cornell University 2008 As a galaxy evolves, its stars change the amounts (abundances) of elements within it. Thusdetermining theabundances of these elementsin differentlocations within a galaxy traces its evolution. This dissertation presents abundances of planetary nebulae in our Galaxy and of H II regions in a nearby galaxy (M51). Observations at optical wavelengths dominated such studies in the past. However, abundances determined from infrared lines have the advantages that they are less affected by extinction and the adopted electron temperature. We employ spectra from the Spitzer Space Telescope Infrared Spectrograph and derive abundances for argon, neon, sulfur, and oxygen. These elements are not usually affected by nucleosyn- thesis in the progenitor stars of planetary nebulae, and thus their abundances trace the amounts of these elements in the progenitor cloud. The abundances of theseelementsinH IIregionstracetheamountsoftheseelementsintheinterstellar medium today. We do a case study of abundances in the planetary nebula IC 2448, finding that it has subsolar abundances, which indicates that the progenitor star formed out of subsolar material. We also derive abundances and assess the dust properties of eleven planetary nebulae in the Bulge of the Milky Way. We find that the abundances from these planetary nebulae do not follow the abundance trend observed in planetary nebulae in the Disk. This points toward separate evolution for the Bulge and Disk components. Additionally, we find peculiar dust proper- ties in planetary nebulae in the Bulge which indicate that the progenitors of these nebulae evolved in binaries. Finally, we make a pilot study of the abundances in H II regions across the galaxy M51. BIOGRAPHICAL SKETCH Shannon was born on May 23, 1979 in Albuquerque, New Mexico to Norman and Sharon Guiles. They all moved to Redlands, California when Shannon was six months old. Her brother, Jason, was born there on February 3, 1981, and Shannon cannot remember life without him. As Shannon grew up, her father helped her when she got stuck on math or science homework and her mother taught her how to learn from books. She also learned a lot from tutoring her brother in math when he wanted help. Shannon graduated from Redlands High School in 1997. She went on to attend the University of California, San Diego (UCSD) where she received her Bachelor’s Degree in Physics in 2001. During her undergraduate years she participated in three Research Experience for Undergraduates (REU) programs: (1) with Prof. Ami Berkowitz at UCSD on magnetic materials, (2) in Prof. Michael Wiescher’s group at the University of Notre Dame in nuclear physics, and (3) with Prof. George Fuller at UCSD in theoretical astrophysics. The most enjoyable of these REU programs was working with George Fuller, who encouraged her in applying to graduate schools, and for part of the year after she graduated she continued to work with him and his graduate student Jason Pruet. In August of 2002, Shannon and her mom took a road trip to Ithaca, New York where Shannon became a graduate student in the Department of Physics at Cornell University. During her first summer in graduate school she worked in biophysics with Prof. Carl Frank, but ultimately decided that biophysics was not for her. After her second year in graduate school she joined Prof. Jim Houck’s group in Astronomy, and she has worked in this group for the last four years, with her work in this group culminating in her dissertation. She also met her husband, Ryan Gutenkunst, while at Cornell, and they married on April 29, 2007. iii To my husband Ryan, my parents Sharon and Norman Guiles, my brother Jason Guiles, and my grandma Frieda Maloney. iv ACKNOWLEDGEMENTS First and foremost, I thank Jeronimo Bernard-Salas, who mentored me during my last two years of research. The work I have done with him forms the bulk of this dissertation. I am grateful to him for paying attention when I needed help, for sharing and explaining his code for calculating abundances, and for finding my mistakes and pointing me in the right direction to fix them (although of course any mistakes left in this dissertation are my fault and not his). Thanks also to Jim Houck for providing me with such a great opportunity to work on data from the Spitzer Space Telescope Infrared Spectrograph. I feel fortunate that I happened to be a graduate student when and where I had the chance to work with data from such an important instrument. Additionally, thanks to all of the other members of my special committee: Terry Herter, Saul Teukolsky, and Ira Wasserman. IthankthepastandpresentmembersoftheSpitzerIRSgroupatCornellwhom I have had the pleasure to work with (in alphabetical order): Don Barry, Jeronimo Bernard-Salas, Bernhard Brandl, Vassilis Charmandaris, Daniel Devost, Duncan Farrah, Elise Furlan, Peter Hall, Lei Hao, Terry Herter, James Higdon, Sarah Higdon, Jim Houck, Jason Marshall, Laurie McCall, Greg Sloan, Henrik Spoon, Keven Uchida, Dan Weedman, and Yanling Wu. All of them have helped me at some point, and their support has meant a lot to me. I would like to single out Don Barry who kept my computer running happily, Elise Furlan for teaching me the intricacies of SMART, Peter Hall for keeping SMART running, Laurie McCall for keeping things in the group running smoothly, Greg Sloan for answering my questions about dust, and Yanling Wu for being a kind and supportive office mate who never hesitated to answer my questions. Thanks to all of my co-authors on the two papers about planetary nebulae. Jeronimo Bernard-Salas and Stuart Pottasch gave me thorough comments and v suggestions on the two papers, which indubitably made the papers fly through the review process with ease; their expertise in the subject helped immensely. Jeronimo also planned the observations on which the second paper was based. Also thanks to my other co-authors on those papers: Tom Roellig (who planned the observations on which the first paper was based), Greg Sloan (who helped with the interpretation of the dust features in the second paper), and Jim Houck (who gave me helpful comments on both papers and donated the IRS GTO time for the observations for the second paper). I also thank Daniel Devost and Terry Herter for helping me with a project to take data at Palomar, and to Thomas Jarrett for showing me how to best use the WIRC instrument there for narrow-band imaging and setting me up to use his data reduction software. Thanks to James Lloyd and Don Banfield for letting me use some of their telescope time to learn how to use the WIRC instrument before my observing run. Thanks also to the night assistant there, Jean Mueller. Also thanks to NASA for funding my research. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through Contract Number 1257184 issued by JPL/Caltech. Additionally,IthankthemembersoftheIthacaAreaToastmastersClub. Their support and positive feedback have helped me improve my public speaking skills, which in turn helped me when I gave presentations on my work and talks for out- reach. I also found their friendship, cheer, and different outlook on life invaluable. Finally, I thank my family. My parents and grandparents always encouraged me to do my best, and without that encouragement I would not be here. My brother is one of my best friends, and I appreciate his support. Most of all, I vi thank my husband Ryan. The rest of my family lives across the country. Ryan’s presence here and his love, support, and encouragement helped buoy me through the deep and sometimes turbulent waters of graduate school. vii TABLE OF CONTENTS Biographical Sketch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi 1 Introduction 1 1.1 Elements and the Evolution of the Galaxy . . . . . . . . . . . . . . 2 1.1.1 Creation of the Elements . . . . . . . . . . . . . . . . . . . . 2 1.1.2 Formation and Evolution of the Galaxy . . . . . . . . . . . . 4 1.2 Photoionization Regions . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2.1 Planetary Nebulae . . . . . . . . . . . . . . . . . . . . . . . 10 1.2.2 H II Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.3 What We Can Learn from Spectra of Photoionization Regions . . . 13 1.3.1 Extinction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.3.2 Electron Density and Temperature . . . . . . . . . . . . . . 14 1.3.3 Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.3.4 Ionizing Radiation Field . . . . . . . . . . . . . . . . . . . . 20 1.4 Dust: Gemstones and Carcinogens in Space . . . . . . . . . . . . . 21 1.4.1 Silicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.2 Polycyclic Aromatic Hydrocarbons (PAHs) . . . . . . . . . . 25 1.5 Observing with the Spitzer Space Telescope . . . . . . . . . . . . . 26 1.6 In This Dissertation . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2 The Spitzer IRS Infrared Spectrum and Abundances of the Plan- etary Nebula IC 2448 30 2.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.3 Spitzer Observations and Data Reduction . . . . . . . . . . . . . . . 32 2.4 Optical and UV Data . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2.5 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.5.1 Extinction Correction . . . . . . . . . . . . . . . . . . . . . . 40 2.5.2 Electron Density . . . . . . . . . . . . . . . . . . . . . . . . 42 2.5.3 Electron Temperature . . . . . . . . . . . . . . . . . . . . . 43 2.5.4 Abundances . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 2.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 viii