A New Set of Spectroscopic Metallicity Calibrations for RR Lyrae Variable Stars
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University of Kentucky UKnowledge Theses and Dissertations--Physics and Astronomy Physics and Astronomy 2014 A New Set of Spectroscopic Metallicity Calibrations for RR Lyrae Variable Stars Eckhart Spalding University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Spalding, Eckhart, "A New Set of Spectroscopic Metallicity Calibrations for RR Lyrae Variable Stars" (2014). Theses and Dissertations--Physics and Astronomy. 22. https://uknowledge.uky.edu/physastron_etds/22 This Master's Thesis is brought to you for free and open access by the Physics and Astronomy at UKnowledge. It has been accepted for inclusion in Theses and Dissertations--Physics and Astronomy by an authorized administrator of UKnowledge. For more information, please contact [email protected]. STUDENT AGREEMENT: I represent that my thesis or dissertation and abstract are my original work. 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Eckhart Spalding, Student Dr. Ron Wilhelm, Major Professor Dr. Tim Gorringe, Director of Graduate Studies A NEW SET OF SPECTROSCOPIC METALLICITY CALIBRATIONS FOR RR LYRAE VARIABLE STARS THESIS A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in the College of Arts and Sciences at the University of Kentucky By Eckhart Spalding Lexington, Kentucky Director: Dr. Ron Wilhelm, Professor of Physics Lexington, Kentucky 2014 c Copyright Eckhart Spalding 2014 ABSTRACT OF THESIS A NEW SET OF SPECTROSCOPIC METALLICITY CALIBRATIONS FOR RR LYRAE VARIABLE STARS RR Lyrae stars are old, iron-poor, Helium-burning variable stars. RR Lyraes are extremely useful for tracing phase-space structures and metallicities within the galaxy because they are easy to identify, have consistent luminosities, and are found in large numbers in the galactic disk, bulge, and halo. Here we present a new set of spectroscopic metallicity calibrations that use the equivalent widths of the Ca II K, Hγ,andHδ lines to calculate metallicity values. Applied to spectroscopic survey data, these calibrations will help shed light on the evolution of the Milky Way and other galaxies. KEYWORDS: RR Lyraes, metallicity calibration, spectroscopy, galactic halo, Sloan Digital Sky Survey Author’s signature: Eckhart Spalding Date: June 21, 2014 A NEW SET OF SPECTROSCOPIC METALLICITY CALIBRATIONS FOR RR LYRAE VARIABLE STARS By Eckhart Spalding Director of Thesis: Ron Wilhelm Director of Graduate Studies: Dr. Tim Gorringe Date: June 21, 2014 To the villagers of Olkiramatian, who are wealthy in beautiful night skies, in which the developed world is increasingly impoverished ACKNOWLEDGMENTS I owe a great deal of thanks to a number of key individuals for making this work possible. Those directly associated with the University of Kentucky include Robert Milton Huffaker (UK, ’57), who generously funded much of the travel costs through Huffaker Travel Scholarships; Dr. Keith MacAdam, who provided the MacAdam Student Observatory to the UK Physics and Astronomy Department; Tim Knauer and Kyle McCarthy, who provided assistance at the MSO; and department Chair Dr. Sumit Das, who released funds to enable me to present results at the 223rd AAS meeting. I am also grateful to Dr. John Kielkopf, for taking some of the photometry at the University of Louisville’s Moore Observatory (and for prodding his colleague Dr. Rhodes Hart to nab a star from Australia, making this project an international col- laboration); David Doss, the eminence grise of McDonald Observatory’s Mt. Locke, for his technical help (and his concern the morning after I hit my head on the spectro- graph); and, of course, the cherubic Dr. Nathan De Lee and my advisor, the pensively barbate Dr. Ron Wilhelm, for all their variegated forms of guidance. A special thanks goes to the viola virtuoso Dr. John Kuehne, the colorful and wild-haired resident elf of the 82-inch dome at McDonald Observatory, for his tireless technical assistance; his eclectic conversations; and for performing all the live music that went into this research. This work made use of the Expeditions and Discoveries: Sponsored Exploration and Scientific Discovery in the Modern Age collection of the Harvard University Library Open Collections Program, and the GCVS database of the Sternberg As- tronomical Institute of the Lomonosov Moscow State University. Here are further iii official acknowledgements: We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. This research has made use of the SIMBAD database, operated at CDS, Stras- bourg, France. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Coun- cil for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Par- ticipating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel Uni- versity, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max- Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pitts- burgh, University of Portsmouth, Princeton University, the United States Naval Ob- servatory, and the University of Washington. iv TABLE OF CONTENTS Acknowledgments.................................. iii TableofContents.................................. v List of Tables . vii ListofFigures ................................... viii Chapter1 :Introduction............................. 1 Chapter2 : ABriefHistoryofRRLyraeResearch. 2 Chapter 3 : The Pulsation Mechanism . 8 Chapter 4 : The Light Curve Shape . 11 Chapter5 : TheImportanceofMetallicityTracing . 14 Chapter6 : ABriefHistoryoftheCalibration . 17 Chapter 7 : The Saha and Boltzmann Equations and Line Formation . 22 Chapter8 :DataAquisition ........................... 25 8.1 Photometry . 25 8.2 Period Data . 27 8.3 Spectroscopy . 28 Chapter 9 : Data Reduction . 31 9.1 Photometry . 31 9.2 Metallicity Values . 31 9.3 Spectroscopy . 32 9.4 FunctionFitting.............................. 34 Chapter 10 : Results . 36 Chapter 11 : Conclusions . 42 Appendices ..................................... 43 Appendix A: Boyden Station During Revolution in Peru .......... 44 Appendix B: Heuristic Species Population Estimates ............ 46 Appendix C: Light Curves and Polynomial Overlays ............. 48 Appendix D: Author Metallicity Comparisons ................ 58 Appendix E: Stripe 82 [Fe/H] Error Calculation ............... 62 v Appendix F: H-K Plots Showing Phase .................... 63 Appendix G: Python Code for Synthetic Data Generation .......... 73 Appendix H: C++ Code for Function Fitting ................. 75 Bibliography . 79 Vita......................................... 89 vi LIST OF TABLES 7.1 Estimates of Species Proportions in an RR Lyrae Photosphere . 23 8.1 Epochs-of-Maximum . 27 8.2 Star Periods . 29 8.3 Metallicities from the Literature . 30 10.1 Calibration Coefficients and Standard Deviations . 36 vii LIST OF FIGURES 2.1 Mt.Harvard,nearChosica,Peru . 6 2.2 BoydenStation,outsidethetownofArequipa . 6 2.3 One of Shapley’s depictions of the distances to globular clusters . 7 2.4 Illustrative simulations of Type I Cepheid and RR Lyrae densities in the galaxy . 7 3.1 AnHRdiagramshowingthelocationsofvariablestars . 10 4.1 AnRRablightcurvetemplate. 12 4.2 AnRRabempiricallightcurve . 12 4.3 AnRRclightcurvetemplate