UNIVERSITY OF CINCINNATI Date:___________________ I, _________________________________________________________, hereby submit this work as part of the requirements for the degree of: in: It is entitled: This work and its defense approved by: Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ Dust Grain Growth and Disk Evolution of a Set of Young Stellar Objects A dissertation submitted to the Division of Research and Advanced Studies of the University of Cincinnati in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Ph.D.) in the department of Physics of the McMicken College of Arts and Sciences 2008 by William Joseph Carpenter B.S. The Ohio State University, 1998 M.S. Miami University of Ohio, 2001 Committee Chair: Prof. Michael Sitko, Ph.D. Abstract This work investigates the observed properties of a sample of young stellar systems using two computer-modeling codes, DUSTY and the Whitney TTSRE codes, to fit the spectra of many objects. The parameters of these computer models are used to attempt to answer several basic questions related to circumstellar disk evolution. Silicate band strengths and millimeter spectral indexes are related to grain growth and are found to be reasonably correlated for the group of models. Circumstellar disk self-shadowing can effect the spectral shape of far infrared data and the relation between the two are studied showing a possible correlation, however other factors can effect the shape of the far infrared data and so a firm correlation can not be confirmed. Six objects out of the nearly 50 stars fit with DUSTY are fit with the Whitney code. Chronological age estimates are compared with model parameters but no correlation could be found between either silicate band strength or millimeter spectral index and the objects’ ages. This indicates that the evolutionary ages and chronological ages of this set of objects are not closely related. For two stars, HD 31648 and HD 163296, time dependent data exists showing differences in the near infrared region. To fit the differing data, the inner radius of the model disk needed to move outwards and the geometrical thickness of the model disk needed to increase. This provides a possible disk evolution scenario to explain the differing spectra. iii iv Acknowledgements I express my deep gratitude to Prof. Sitko for all of his patient assistance in the completion of this project. I also thank him for giving me the opportunity to visit telescopes both in Arizona and Hawaii- even if it was up on a mountain and not down by the beach. I thank Moshe Elitzur, Barb Whitney, and all those legions of people that came before me and wrote the codes used in this project so I didn’t have to. Finally, I super thank my wonderful wife, Amelia, for having such patience with me during these years and for supporting me so much! I also want to thank the two new Carpenters, Ali and Jimmy, for being so awfully cute and also for not demanding TOO much of my time and allowing me to finish! v Table of Contents 1. Introduction 11 2. Background Science 14 2.1. Young Star Formation 14 2.2. Circumstellar Material 16 2.3. Light Interaction with Dust 21 2.4. SED Modeling Codes 30 2.5. Nature and Use of the DUSTY Code 30 2.6. Nature and Use of the Whitney Code 40 3. DUSTY Fits and Results 54 3.1. AA Tau 63 3.2. AB Aur 64 3.3. BF Ori 66 3.4. BFS60 67 3.5. CO Ori 68 3.6. CQ Tau 70 3.7. CW Tau 72 3.8. CY Tau 73 3.9. DG Tau 75 3.10. DL Tau 77 3.11. DM Tau 78 3.12. GI Tau 80 3.13. GK Tau 81 1 3.14. GM Aur 83 3.15. GW Ori 85 3.16. HD 31648 86 3.17. HD 35187 88 3.18. HD 37806 89 3.19. HD 45677 90 3.20. HD 50138 93 3.21. HD 58647 94 3.22. HD 98800 96 3.23. HD 100546 98 3.24. HD 135344 (SAO 206462) 100 3.25. HD 141569 102 3.26. HD 163296 104 3.27. HD 169142 106 3.28. HD 190073 108 3.29. HD 250550 109 3.30. Hen 3-600 110 3.31. HK Ori 112 3.32. HL Tau 114 3.33. HP Tau 116 3.34. HP Tau G2 117 3.35. HP Tau G3 118 3.36. HR 4796 120 2 3.37. LkCa 15 121 3.38. LkCa 21 123 3.39. NV Ori 124 3.40. RR Tau 125 3.41. RW Aur 127 3.42. RY Ori 129 3.43. RY Tau 130 3.44. SU Aur 131 3.45. TW Hya 133 3.46. UX Ori 134 3.47. UY Aur 136 3.48. V590 Mon 137 3.49. V594 Cas 138 3.50. XZ Tau 140 3.51. Grain Growth and Settling Correlation 141 3.52. Disk Inner Wall and Self Shadowing Correlation Study 143 4. Whitney Code Fits and Results 150 4.1. HD 31648 155 4.2. HD 163296 162 4.3. Inner Disk Analysis 169 4.4. HD 100546 174 4.5. HD 135344 (SAO 206462) 179 4.6. HD 169142 183 3 4.7. AB Aur 190 4.8. Discussion 194 5. Conclusions 198 6. References 202 7. Appendix A 215 4 List of Figures 2-1 Sample SED and drawing of a Class II object 15 2-2 Basic flared disk model 18 2-3 More complex disk model with hole and ‘puffed up’ inner rim 19 2-4 Example close up SED of the NIR spectral region of HD 163296 20 2-5 Cartoon showing two suggested sources of excess NIR emission 20 2-6 Cartoon of stellar radiation incident on a grain and resulting emission 22 2-7 Wavelength dependence of Qabs 24 2-8 Wavelength dependence of Qabs for several grain sizes 25 2-9 Emission spectra of a 1000K blackbody and three grain types 25 2-10 Temperature vs. stellar distance for several grain types 27 2-11 Temperature vs. stellar distance for several grain sizes 27 2-12 DUSTY SED internal coded DL-Silicates and C# Mie code DL-Silicates 30 2-13 The DUSTY code model 31 2-14 An example of DUSTY halo disk reheating 33 2-15 The SED of HD 31648 as an example of limited grain growth 37 2-16 The SED of XZ Tau as an example of more advanced grain growth 38 2-17 An example SED of a ‘toy’ model for an early stage stellar system 39 2-18 The SED of HD 58647 40 2-19 Density plots of inner disk region and halo envelope 41 2-20 The SED of HD 135344 42 2-21 Cutaways diagrams showing cavity wall shape 43 2-22 Flattened envelope density structure and inner region disk structure 44 5 2-23 Schematic of the four dust file regions 45 2-24 Image file showing a face on object 48 2-25 Example of the same model with different photon counts 49 2-26 Whitney code produced model of Type 0 SED 50 2-27 Whitney code produced model of Type II SED 51 2-28 Density plot of a Whitney model disk with flaring parameter B=1.12 52 2-29 Density plot of a Whitney model disk with flaring parameter B=0.86 52 3-1 Comparison of pyroxene60 with olivine 56 3-2 Comparison of adding graphite and increasing the grain size 57 3-3 Comparison of replacing DL-Silicates with pyroxene 58 3-4 The SED and DUSTY model of AA Tau 63 3-5 The SED and DUSTY Model of AB Aur 64 3-6 The SED and DUSTY model of BF Ori 66 3-7 The SED and DUSTY model of bfs60 67 3-8 The SED and DUSTY model of CO Ori 68 3-9 The SED and DUSTY model of CQ Tau 70 3-10 The SED and DUSTY model of CW Tau 72 3-11 The SED and DUSTY model of CY Tau 73 3-12 The SED and DUSTY model of DG Tau 75 3-13 The SED and DUSTY model of DL Tau 77 3-14 The SED and DUSTY model of DM Tau 78 3-15 The SED and DUSTY model of GI Tau 80 3-16 The SED and DUSTY model of GK Tau 81 6 3-17 The SED and DUSTY model of GM Aur 83 3-18 The SED and DUSTY model of GW Ori 85 3-19 The SED and DUSTY model of HD 31648 86 3-20 The SED and DUSTY model of HD 35187 88 3-21 The SED and DUSTY model of HD 37806 89 3-22 The 1980 SED and DUSTY model of HD 45677 90 3-23 The 1992 SED and DUSTY model of HD 45677 91 3-24 The SED and DUSTY model of HD 50138 93 3-25 The SED and DUSTY model of HD 58647 consisting of a disk and 94 blackbody 3-26 The SED and DUSTY model of HD 58647 consisting of a large grain 95 halo 3-27 The SED and DUSTY model of HD 98800 96 3-28 The SED and DUSTY model of HD 100546 98 3-29 The SED and DUSTY model of HD 135344 100 3-30 The SED and DUSTY model of HD 141569 102 3-31 The SED and DUSTY model of HD 163296 104 3-32 The SED and DUSTY model of HD 169142 106 3-33 The SED and DUSTY model of HD 190073 108 3-34 The SED and DUSTY model of HD 250550 109 3-35 The SED and DUSTY model of Hen 3-600 110 3-36 The SED and DUSTY model of HK Ori 112 3-37 The SED and DUSTY model of HL Tau 114 7 3-38 The SED and DUSTY model of HP Tau 116 3-39 The SED and DUSTY model of HP Tau G2 117 3-40 The SED and DUSTY model of HP Tau G3 118 3-41 The SED and DUSTY model of HR 4796 120 3-42 The SED and DUSTY model of LickCa 15 121 3-43 The SED and DUSTY model of LickCa 21 123 3-44 The SED and DUSTY model of NV Ori 124 3-45 The SED and DUSTY model of RR Tau 125 3-46 The SED and DUSTY model of RW Aur 127 3-47 The SED and DUSTY model of RY Ori 129 3-48 The SED and DUSTY model of RY Tau 130 3-49 The SED and DUSTY model of SU Aur 131 3-50 The SED and DUSTY model of TW Hya 133 3-51 The SED and DUSTY model of UX Ori 134 3-52 The SED and DUSTY model of UY Aur 136 3-53 The SED and DUSTY model of V590 Mon 137 3-54 The SED and DUSTY model of V594 Cas 138 3-55 The SED and DUSTY model of XZ Tau 140 3-56 Band/continuum ratio and millimeter spectral index correlation 142 3-57 12µm/25µm correlation plot showing all selected objects 145 3-58 12µm/25µm correlation plot with “questionable” objects removed 145 3-59 12µm/60µm correlation plot showing all selected objects 146 3-60 12µm/60µm correlation plot with “questionable” objects removed 146 8 3-61 25µm/60µm correlation plot showing all selected objects 147 3-62 25µm/60µm correlation plot with “questionable” objects removed 147 4-1 The 1996 SED and Whitney model of HD 31648 155 4-2 The 2004 SED and Whitney model of HD 31648 155 4-3 Model Comparison of HD 31648 from 1996 and 2004 156 4-4 Surface brightness plot of HD 31648 158 4-5 Temperature