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INTERSTELLAR EXTINCTION IN THE ORION ASSOCIATION Item Type text; Dissertation-Reproduction (electronic) Authors Lee, Thomas Alan, 1939- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 04/10/2021 12:54:51 Link to Item http://hdl.handle.net/10150/284825 This dissertation has been microfilmed exactly as received 67-6936 LEE, Thomas Alan, 1939- INTERSTELLAR EXTINCTION IN THE ORION ASSOCIATION. University of Arizona, Ph.D., 1967 Astronomy University Microfilms, Inc., Ann Arbor, Michigan INTERSTELLAR EXTINCTION IN THE ORION ASSOCIATION by Thomas Alan Lee A Dissertation Submitted to the Faculty of the DEPARTMENT OF ASTRONOMY In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 19 6 7 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE I hereby recommend that this dissertation prepared under my direction by Thomas A. Lee entitled Interstellar Extinction in the Orion Association be accepted as fulfilling the dissertation requirement of the degree of Doctor of Philosophy ? Cj /ty fid? Dissertation Director Date After inspection of-the dissertation, the following members of the Final Examination Committee concur in its approval and recommend its acceptance:* r. 4)oJlh* &ZrL£-£ S-& a)cKT~ hfa >~) o Aj ns h ( *This approval and acceptance is contingent on the candidate's adequate performance and defense of this dissertation at the final oral examination. The inclusion of this sheet bound into the library copy of the dissertation is evidence of satisfactory performance at the final examination. STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of the requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allow­ able without special permission, provided that accurate acknowledgment of the source is made. Requests for permis­ sion for extended quotation from or reproduction of this manuscript in v/hole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. cif Jfl / SIGNED: ACKNOWLEDGMENTS It is a pleasure to thank the many people who aided me in the various phases of this work. Assistance from the following individuals is hereby gratefully acknowledged: Mrs. Kathryn Sheffer for managing the data process­ ing and being helpful in many, many ways; Mr. Richard Mitchell for helpful discussions con­ cerning photometric systems and data analysis; Mr. Braulio Iriarte and Dr. Manuel Mendez for courtesies extended to me during a pleasant and rewarding visit to Mexico; Dr. Guillermo Haro for allowing me to take several of his infrared plates to Tucson for copying and detailed study; Dr. Bart Bok for his interest, encouragement., and helpful suggestions; Drs. Manuel Mendez and Robert Williams for interest ing and valuable discussions; Mr. Ed Howell for his help with photographic problems; Mrs. Helena Davis and Miss Judy Ackerman for assist ing in the preparation of the final draft; iii iv Mrs. Dorothy Conniff for typing the final draft; and all the personnel of the Lunar and Planetary Laboratory v/ho helped make this project so enjoyable. I am greatly indebted to Dr. Harold L. Johnson, v/ho directed this research and made the photometric equipment of the Lunar and Planetary Laboratory available for this investigation. He has given freely of his time and energy in providing continued guidance and encouragement. The consideration and interest he has shown are deeply appreci­ ated . This project was supported by the National Science Foundation under grants GP 3^-1^ and GP 5129. TABLE OF CONTENTS Page LIST OP FIGURES "J"- vii LIST OF TABLES ix ABSTRACT x I. Introduction 1 A. Observational Work 1 B. Theoretical Results 10 C. The Orion Region 19 1. General 19 2. Extinction in the Orion Nebula .... 19 II. Observational Data 25 A. Selection of Stars 25 B. Equipment and Techniques . 25 C. The Data 30 III. Intrinsic Colors of Early-Type Stars 43 A. Unreddened Early-Type Stars 43 B. The U-B and B-V Color Indices ....... 43 C. The Infrared Color Indices 46 D. The V-L Index 51 IV. Extinction Curve Calculations 54 A. Method 54 1. Color Excesses 54 v vi 2. Normalization and Scaling 54 B. The Ratio 55 V. Regional Mean Extinction Laws 59 A. Probable Errors and Weights 59 B. Properties of the Regional Laws 69 VI. Related Phenomena Modifying the Extinction Interpretation 80 A. The 'Belt' Region 80 B. The 'Sword' Region 83 1. Anomalous Energy Distributions .... 83 2. Nebular Radiation 86 3. Paint Red Stars in the Orion Nebula . 95 VII. Regional Monochromatic Extinction Laws 102 A. Method 102 B. General Properties of Wideband Extinction Laws 105 C. Regional Monochromatic Curves Ill D. Properties of the Monochromatic Laws .... 121 VIII. Discussion . 126 A. Regions of 'Normal' Extinction 126 B. Regions of 'Anomalous' Extinction 127 C. Extinction and Nebulosity 131 D. Monochromatic Extinction Laws 136 IX. Conclusions 143 APPENDIX A 1^5 APPENDIX 1^7 REFERENCES 164 LIST OP FIGURES Page 1. Schematic Extinction Curve *!• 2. Normalized Extinction Curves for the Cepheus and Scorpius Regions (Johnson, 1966a) 8 3. Theoretical Extinction Curves (van de Hulst, 1949) 13 4. Normalized Filter-Cell Response Functions .... 28 5 • V-R versus B-V for 0 and B 0 Stars 48 6. V-I versus B-V for 0 and B 0 Stars 49 7. V-K versus B-V for 0 and B 0 Stars 50 8. K-L versus I-K for B 1 and Earlier-Type Stars . 53 9. Normalized Extinction Laws for the Orion East 'Belt' and NGC 2024 No. 1 71 10. Normalized Extinction Laws for M 78 A, B and the Northwestern Region 72 11. Normalized Extinction Laws for the Outer 'Sword.' HD 37061, and the Trapezium Region 73 12. Schematic Map of Extinction Regions in the I Orion Association 74 13. Orion 'Belt' Color-Magnitude Diagram—Corrected for Extinction 82 14. East-West Division of the 'Belt' Region 82 15. Infrared Photograph of the Orion 'Sword' 89 16. Infrared Photograph of the Orion Nebula 90 17. 01 Orionis 91 18. Mean Normalized Emission Spectrum Required for 'Normal1 Extinction in the Orion Trapezium .... 94 vii viii Page 19. Map of the Orion Trapezium Region (Parenago., 1954) 99 20. versus Efor 0-type Stars in Cygnus . .108 21. versus Eg_^. for 0-type Stars in Cygnus .... 109 22. Normalized Extinction Curves for Two Stars whose Color Temperatures are 3.>500 and 30,000 Degrees 110 .23. Normalized Monochromatic Extinction Lav; for the East 'Belt' Region 113 24. Normalized Monochromatic Extinction Lav/ for NGC 2024 No. 1 114 25. Normalized Monochromatic Extinction Law for the Northwestern Region 115 26. Normalized Monochromatic Extinction Law for M 78 A, B 116 27• Normalized Monochromatic Extinction Lav; for the Outer 'Sword' Region . 117 28. Normalized Monochromatic Extinction Law for HD 37061 Ho 29. Normalized Monochromatic Extinction Law for the Trapezium Region (exact fit) 119 30. Normalized Monochromatic Extinction Law for the Trapezium Region (smoothed) 120 31. versus Distance from 01 Orionis 129 32a. Extinction from Combined Distributions of Particle Sizes 139 32b. Extinction from Combined Distributions of Particle Sizes ..... 140 LIST OF TABLES Page 1. Effective Wavelengths and Reciprocal Effective Wavelengths for the Photometric Filters 26 2. UBVRI Observations 32 3. UBVRIJKL Observations 4l 4. Unreddened Early-Type Stars 44 5- Intrinsic Color Indices of Early-Type Main Sequence Stars 45 6. Intrinsic Color Indices of Early-Type Super- giants 45 7. The E^_y/Eg_^. Ratio in Orion 57 8. Color Excess Ratios 60 9. Observational Errors 65 10. Errors of Intrinsic Colors of 0 and B Stars .... 65 11. Probable Errors of Color Excesses for N Observations 68 12. Regional Extinction Data 70 13. Extinction Laws for 01 Orionis if Unseen Companions are Present 85 14. Normalized Monochromatic Extinction Data 112 15. Observed and Monochromatic Color Excess Ratios . 122 ix ABSTRACT Photoelectric photometry, covering a spectral region from X = .36 i-i to 3*4- u* is obtained for a large sample of early-type stars in the I Orion association with the photo­ metric telescopes of the Lunar and Planetary Laboratory of the University of Arizona. The observations are interpreted in terms of the interstellar extinction phenomenon. The color excesses of the stars are calculated from the observed (reddened) and intrinsic (unreddened) color indices. Nor­ malized curves revealing the wavelength dependence of the extinction are then computed. Because of the low reddeninr in many parts of the association, the errors of the extinc­ tion curves are often large. For this reason, regional mean extinction laws are determined from the data of individual stars in localized areas. A method that eliminates the use of filter effective wavelengths is then employed to obtain the corresponding monochromatic extinction laws. The extinction in a large fraction of the association is essentially 'normal.' However, two regions, one in the east 'Belt' near C Orionis and the other in the center of the Orion Nebula (NGC 1976), exhibit distinctly 'non-normal' extinction characteristics. The anomalies found in these regions are a steeper extinction gradient in the infrared x xi and a high ratio of total to selective absorption. The Orion Nebula region is studied in considerable detail.
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