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Information to Users INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter fece, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely afreet reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zed) Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 A STUDY OF ATTENUATION EFFECTS IN HIGHLY INCLINED SPIRAL GALAXIES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Leslie E. Kuchinski, M.S. ***** The Ohio State University 1997 Dissertation Committee: Appro^^ by Professor Donald M. Terndrup, Adviser 7A /J ^ .-Vdviser Professor Kristen Sellgren Department of Astronomy DMI Number: 9 801728 UNn Microform 9801728 Copyright 1997, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 ABSTRACT This dissertation presents a quantitative study of the attenuation of stellar light by dust in highly inclined spiral galaxies. BVRIJHK images of 15 Sab-Sc galaxies with inclination angles greater than 65° are used to explore which properties of radiative transfer models are required to describe the reddening of optical and near-infrared (NIR) colors across galaxy dust lanes. The models are then used to predict line-of- sight and face-on optical depths through these systems. Preliminary comparisons of the dust lane color gradients to predictions from models with simple slab or spherical shapes and several different relative dust-star geometries demonstrates that no single model of this type adequately describes the observed reddening over the entire optical- NIR spectral baseline. The NIR colors are best fit by screen geometries and are not well reproduced by models with mixed dust and stars that have unextinguished light sources near the edge of the dust distribution. However, only those models with a mixture of dust and stars produce the saturation of reddening observed in the dust lane optical colors. More sophisticated disk galaxy radiative transfer models with exponential stellar and dust disks, bulge components, multiple scattering, and both homogeneous and clumpy dust distributions provide much better simultaneous agreement to the optical and NIR dust lane color gradients. I use several of the 11 radiative transfer models to infer values for the V’-band optical depth ry through these galaxies and find the result to be highly dependent on the adopted dust-star geometry. When compared to the extent of reddening predicted by the disk galaxy models, which are the most physically plausible ones used here and provide the best prediction of galaxy color gradients, the maximum dust lane color excesses imply central face-on optical depths of rv.o = 0.5 — 2.0. I find no evidence from the galaxy colors to support the recent claim that spiral disks are opaque out to D0 5 . Finally, I briefly discuss implications of the model comparisons and inferred optical depths for some techniques used to study spiral galaxy structure and stellar content. Ill ACKNOWLEDGMENTS I cannot thank by name every individual whose support made this thesis possible, but there are numerous people whose contributions have been substantial. Many thanks to my adviser, Don Terndrup, for keeping this thesis going as it evolved rapidly from what was originally planned. Also for understanding how as­ tronomy is just one part of life. I am grateful to Adolf Witt and Karl Gordon, whose efforts to model attenuation effects in galaxies were not only invaluable to this project but are also a significant contribution to astronomy. I am also grateful to many (most?) members of the OSU Astronomy Department. Special thanks to .Jay Frogel and Kris Sellgren, who kept in touch and were always available for advice and critiques. Rick Pogge, Alice Quillen, Brad Peterson, and Darren DePoy provided a great deal of intellectual and moral support. I thank my fellow graduate students, especially Glenn, Bob, and Anita, for celebrating and commiserating with me. Finally, I acknowledge with deep gratitude the support of my family. I thank my parents for encouraging an interest in science and the beauty of the universe from a very young age. And of course a huge thanks to Kevin, Ryan, and K2, whose love, companionship, support, and sacrifices over the past several years have kept me going and have shown me some of the happiest times of my life. IV VITA March 13,1969 ..................................................... Born — Madison, VVI 1991 ....................................................................... B.S. (Physics), Duke University, Durham, North Carolina 1991 ....................................................................... Multiple Year University Fellowship, The Ohio State University 1993 ....................................................................... M.S. (Astronomy), The Ohio State University 1991-present ........................................................ Graduate Fellow, Teaching and Re­ search Associate, The Ohio State Uni- versitv Publications Research Publications (refereed) Quillen, A.C., Kuchinski, L.E., Frogel, .J.A., k. DePoy, D.L. 1996, "Discovery of a Boxy Peanut-Shaped Bulge in the Near-Infrared”, The Astrophysical Journal 481. 179. Kuchinski, L.E. & Terndrup, D.M. 1996, "Infrared Photometry and Dust .-Absorption in Highly Inclined Spiral Galaxies”, The Astronomical Journal 111, 1073. Kuchinski, L.E. k Frogel, 1995, "Infrared .Array Photometry of Metal Rich Globular Clusters III: Two More Clusters and an .Analysis of U — K Colors”, The Astronomical Journal 110, 2844. Frogel, J..A., Kuchinski, L.E., k Tiede, G.P. 1995, "Infrared .Array Photometry of Metal Rich Globular Clusters IT. Filler 1 - The Most Metal Rich Cluster?”, The Astronomical Journal 110, 1154. Kuchinski, L.E., Frogel, J.A., Terndrup, D.M., k Persson, S.E. 1995, “Infrared .Array Photometry of Metal Rich Globular Clusters I: Techniques and First Results”, The Astronomical Journal 110, 1131. Quillen, A.C., Frogel, J.A., Kuchinski, L.E., & Terndrup, D.M. 1995, “Multiband Images of the Barred Galaxy NGC 1097” , The Astronomical Journal. 110, 156. Research Publications (unrefereed abstracts) Kuchinski, L.E., Terndrup, D.M., Witt, A.N., & Gordon, K.D. 1996 “The Impact of Dust on Photometric Studies of Spiral Galaxies”, Bulletin of the American Astro­ nomical Society, 28, no.4, 1303. Kuchinski, L.E. & Terndrup, D.M. 1995, “Infrared Photometry and Dust Absorption in Edge-On Spiral Galaxies”, Bulletin of the American Astronomical Society, 27. no.4, 1353. Kuchinski, L.E. & Terndrup, D.M. 1995, “Infrared Photometry and Dust Absorption in Edge-On Spiral Galaxies”, New Extragalactic Perspectives in the New South Africa, ed. D.L. Block &: J.M. Greenberg, (Dordrecht: Kluwer), 178. Fields of Study Major Field: .A.stronomy Studies in: .■Vttenuation Eflfects in Spiral Galaxies Prof. D.M. Terndrup Near-Infrared Studies of Globular Clusters Prof. .LA. Frogel Spiral Galaxy Structure and Formation Prof. D.M. Terndrup VI TABLE OF CONTENTS Page A b stra c t .................................................................................................................................. ii Acknowledgments ............................................................................................................. iv V i t a ......................................................................................................................................... V List of T a b le s .................................................................................................................... ix List of Figures ................................................................................................................. x Chapters: 1 Introduction ............................................................................................................... 1 1.1 Interstellar Dust and Relevant Physical Processes ............................... 1 1.2 Implications of Dust for Photometric Studies of Spiral Galaxies . 5 1.3 Previous Studies of Opacity and .Atténuation Eflfects inSpirals . 6 1.4 Overview of this thesis ............................................................................... 11 2 Acquisition and Reduction of D a ta ..................................................................
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