Debris Disks in Open Stellar Clusters Item Type text; Electronic Dissertation Authors Gorlova, Nadiya Igorivna 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 23/09/2021 12:45:37 Link to Item http://hdl.handle.net/10150/195908 DEBRIS DISKS IN OPEN STELLAR CLUSTERS by Nadiya Igorivna Gorlova 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 2 0 0 6 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dis- sertation prepared by Nadiya Igorivna Gorlova entitled Debris Disks in Open Stellar Clusters and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy. Date: 8 September 2006 George Rieke Date: 8 September 2006 Renu Malhotra Date: 8 September 2006 Michael Meyer Date: 8 September 2006 James Muzerolle Final approval and acceptance of this dissertation is contingent upon the candi- date's submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. Date: 8 September 2006 Dissertation Director: George Rieke 3 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the Univer- sity Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permis- sion, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her 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. SIGNED: Nadiya Igorivna Gorlova 4 ACKNOWLEDGMENTS It was a long and bumpy road, from the small town on the Danube river to astronomers retreat in Arizona. I am writing with the memory of my friends and my family members in Ukraine whose difficult life paths I could repeat if I didn't come across the following wonderful people. Zinaida Antonovna, my math teacher, gave me the first sound appreciation for science. My parents checked my home-works regularly, and with their scoldings made me wish to compete and succeed. My sister allowed me to help her with math problems, and my English is largely due to listening to her long memorizing exercises. I am also indebted to my advisors at the Odessa observatory – Valery Kovtyukh and Sergei Andrievsky. My family would not be able to support my fancy with as- tronomy forever, but luckily I got the scholarship from the Vatican Observatory. George Coyne and other Jesuits provided advice and warm parties throughout all the years in Tucson. George Rieke, my PhD advisor, taught me to believe in data and myself. With his enthusiasm, sense of humor, respect to other people's work, and care for his every student, he will always serve an example of insight- ful researcher, administrator, and mentor. And it was always a pleasure to savor Marcia's treats at their welcoming home :) My first advisor Michael Meyer intro- duced me to brown dwarfs, awk and research notebook, scrupulously marked up drafts, and contributed in many other indispensable ways in my scientist's formation, but most importantly (I think) he taught me how to stand on your own feet. Special thanks to James Muzerolle, one of great MIPS postdocs, first for help with Spitzer reductions, and for excellent advising, being always available for questions. Renu Malhotra provided some valuable insights from the plan- etary science point of view. I have enjoyed a nice working environment in the MIPS group. Everyone was friendly and helpful, it really felt like working in the team, with common spirit and goal. I also enjoyed a pleasant co-habitat with my great officemates: the beer'n fries giant Eric, IT specialist and soccer superstar Yu- jin, Nickolas Match-making, Comic relief & Co., the Bing Bang queen Hee-Jong, Jeremiah the philosopher, and the morning bird Wilson. The sweet secretaries is a hidden treasure of Steward. Michelle, Erin, Joy, Catalina, Carmen, Lee Ann – thank you for all your honest dedication to your work, and for shoulders to cry on! Amaya is more than a friend. She was my housemate, officemate, col- league, coach, counselor, and what not! She has become a true role model for me. I want to mention also my other friends – Almudena, Doug, Iva, Ive, Jean, Kate, Serena, Valentin, Vladimir; people who helped on observing runs – Erick, Jim, Julia, Marcia, Morten; people who helped me with data reduction – Chad, Jason, Kurtis, Myra; Jeff and Neal for the excellent computer support; Steward faculty; fellow gradstudents; collaborators; and many other people whom I owe the existence of this thesis or had otherwise pleasant encounter with during the years in gradschool. 5 DEDICATION To my Parents and Teachers » » 6 TABLE OF CONTENTS LIST OF FIGURES . 8 LIST OF TABLES . 9 ACRONYMS . 10 ABSTRACT . 11 CHAPTER 1 INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : 12 1.1 The Birth of a Star . 12 1.2 Formation of Planets and Debris Disks . 17 1.3 Why Clusters? Motivation for This Study . 22 CHAPTER 2 24 MICRON SURVEY OF DEBRIS DISKS IN M47 : : : : : : : : : : 27 2.1 Introduction . 27 2.2 New Observations . 28 2.2.1 Spitzer Measurements . 28 2.2.2 Optical Spectroscopy . 31 2.3 Cluster Membership and Spitzer Detections . 31 2.4 Discussion . 35 2.4.1 Early type stars . 37 2.4.2 Late type stars . 39 2.5 Conclusions . 42 CHAPTER 3 24 MICRON SURVEY OF DEBRIS DISKS IN THE PLEIADES : : : 43 3.1 Introduction . 43 3.2 Observations and Data Reduction . 48 3.3 Sample . 52 3.4 Excess objects . 58 3.5 Properties of the debris disk candidates . 65 3.5.1 IRAC excesses . 65 3.5.2 Model Spectral Energy Distributions . 65 3.5.3 Binarity . 67 3.5.4 Rotation . 70 3.5.5 X-rays . 70 3.6 Lifetime of the 24 ¹m excess . 73 3.7 Conclusions . 79 CHAPTER 4 MID-IR SURVEY OF DEBRIS DISKS IN NGC 2547 : : : : : : : : 81 4.1 Introduction . 81 4.2 Observations and Data Reduction . 83 4.2.1 Spitzer Photometry . 83 7 TABLE OF CONTENTS — Continued 4.2.2 Multi-slit Spectroscopy . 88 4.3 Identifying Excess Candidates . 95 4.3.1 Cluster Membership . 95 4.3.2 IRAC Excesses . 97 4.3.3 MIPS Excesses . 101 4.4 Spectroscopic Subsample . 108 4.5 Properties of the Excess Candidates . 111 4.5.1 8 ¹m excesses . 111 4.5.2 24 ¹m excesses . 115 4.6 Discussion . 117 4.6.1 Evolution of 8 ¹m excess . 117 4.6.2 Transitional disks at 30 Myr? . 121 4.7 Conclusions . 124 CHAPTER 5 CONCLUSIONS AND FUTURE WORK : : : : : : : : : : : : : : : 126 REFERENCES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 132 8 LIST OF FIGURES 1.1 Simulated image of accretion disk around T Tau star . 14 1.2 Images of debris disks . 21 1.3 The effect of close encounters on disks in young clusters . 23 2.1 24 ¹m image of M47 . 30 2.2 J–H vs. K– 24 diagram of M47 . 36 f g 2.3 Spectra of M47 stars with strong 24 ¹m excess . 41 3.1 24 ¹m image of the Pleiades . 50 3.2 Zoomed-in images of stars in the Pleiades field . 59 3.3 Pleiades color-magnitude diagram . 60 3.4 V–K vs. K– 24 diagram of the Pleiades . 61 f g 3.5 24 ¹m images of the debris disk candidates . 66 3.6 X-ray properties of the solar-type stars . 72 3.7 24 ¹m excess fraction as a function of age . 76 4.1 Spitzer mosaic of NGC 2547 . 84 4.2 Photometric and spectroscopic coverage of the cluster . 86 4.3 V–K vs. K– 8 color-color diagram . 99 f g 4.4 R–K vs. K– 8 color-color diagram . 100 f g 4.5 V–K vs. K– 5.8 color-color diagram . 102 f g 4.6 R–K vs. K– 5.8 color-color diagram . 103 f g 4.7 V–K vs. K– 24 color-color diagram . 104 f g 4.8 R–K vs. K– 24 color-color diagram . 105 f g 4.9 Spectral sequence of members using IMACS spectra . 109 4.10 Distribution of radial velocities . 112 4.11 IMACS spectra of excess members . 116 4.12 Spectral energy distributions of stars with 8 ¹m excess . 122 5.1 Combined V–K vs. K– 24 diagram for investigated clusters . 127 f g 5.2 Evolution of dusty disks based on excess fractions . 130 5.3 Evolution of the 24 ¹m excess . 131 9 LIST OF TABLES 2.1 Photometry of M47 members . 33 2.1 Photometry of M47 members . 34 2.2 Properties of the 24 ¹m excess stars in M47 . 38 3.1 Pleiades members with contaminated 24 ¹m photometry . 53 3.1 Pleiades members with contaminated 24 ¹m photometry . 54 3.2 Pleiades members with reliable 24 ¹m photometry .