Low-mass star formation and the initial mass function in young clusters Item Type text; Dissertation-Reproduction (electronic) Authors Luhman, Kevin Lee, 1971- 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 01/10/2021 22:31:04 Link to Item http://hdl.handle.net/10150/288884 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 face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. 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Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zedj Road, Ann Aibor MI 48106-1346 USA 313/761-4700 800/521-0600 LOW-MASS STAR FORMATION AND THE INITIAL MASS FUNCTION IN YOUNG CLUSTERS by Kevin Lee Luhman 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 9 8 DMI Nxunber: 9901759 UMI Microform 9901759 Copyright 1998, 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 THE UNIVERSITY OF ARIZONA ® GRADUATE COLLEGE As members of the Final Examination Committee, we certify that we have read the dissertation prepared by Kevin Lee Luhman entitled Low-Mass Star Formation and the Initial Mass Function in Young Clusters and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy George Rii/k( James Liebert Date Erick Young Date Jonathan Lunine Date Date Final approval and acceptance of this dissertation is contingent upon the candidate's submission of the final copy 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. Di^sertatiorT^irector George Rieke Date 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 University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, 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: 4 ACKNOWLEDGMENTS An important factor in a successful thesis is a good advisor, and I couldn't have asked for a better one than George Rieke. The tireless efforts of George and Marcia in supporting countless observing runs are greatly appreciated. They've shown incredible patience and understanding while training myself and other young scientists. In addition, I thank George and Marcia for obtaining the grant which has supported me during much of my tenure at Steward (NASA grant NAGW-4083 under the Origins of Solar Systems program). Jim Liebert has played an important role as an educator, colleague, and fellow Kansas Jayhawks fan. I'm very grateful to Chad Engelbracht for writing the scripts used in reducing FSpec data and for putting up with my persistent questions concerning latex, perl, fortran, IRAF, etc. I thank Tim Pickering and Craig Kulesa for the computer expertise they've made available to myself and the rest of Steward. Chad, Tim, and Craig also acted as plump and readily explodable targets for my quad rockets in Quake, although not by their own volition. Margaret Hanson and Chad have provided a great deal of assistance and stimulating conversations regarding general observing and science in the infrared. The large amount of observing time which produced the data presented in this thesis was made possible by the generosity of the Steward telescope allocation committee. I thank several scientists for providing helpful comments and access to their data and theoretical calculations: F. Allard, I. Baraffe, A. Burrows, F. D'Antona, L. Hartmann, G. Herbig, J. D. Kirkpatrick, M. Meyer, .J. Stauffer, and F. Svvenson. DEDICATION For Michael and Laurie. 6 TABLE OF CONTENTS LIST OF FIGURES 10 LIST OF TABLES 13 ABSTRACT 14 1 Introduction 15 2 Testing Theoretical Evolutionary Tracks 18 2.1 Introduction 18 2.2 CM Dra and \'Y Gem 19 2.3 Pleiades and Globular Clusters 19 2.4 Which Tracks Are Appropriate for Young, Embedded Clusters? ... 20 3 A Young Object Near the Hydrogen Burning Limit: V410 X-ray 3 24 3.1 Introduction 24 3.2 Observations 26 3.3 Discussion 27 3.3.1 Spectroscopic Results: Li Detection and Spectral Type .... 27 3.3.2 Colors, Extinction, and Bolometric Luminosity 28 3.3.3 H-R Diagram 29 3.4 Conclusions 31 4 A Young Object Below the Hvdrogen Burning Limit: p Oph 162349.8 — 242601 " 37 4.1 Introduction 37 4.2 Observations 39 4.3 Discussion 40 4.3.1 Cluster Membership 40 4.3.2 Spectral Type and Effective Temperature 41 4.3.3 Extinction and Bolometric Luminosity 43 I TABLE OF CONTENTS — Continued 4.3.4 Age and Mass 44 4.4 Conclusion 45 5 L1495E 49 5.1 Introduction 49 5.2 Observations 51 5.3 Discussion 53 5.3.1 IR Spectral Classification of Young Stars 53 5.3.2 Derivation of Ten 55 5.3.3 Derivation of Lboi 58 5.3.4 H-R Diagram 60 5.3.5 The Initial Mass Function 63 5.4 Conclusions 71 5.5 Notes on IR Spectral Classification 73 5.6 Comments on Individual Source Classifications 79 6 IC 348 107 6.1 Introduction 107 6.2 Observations 108 6.3 Individual Source Characteristics 112 6.3.1 Spectral Types 112 6.3.2 Substellar Members of IC 348 115 6.3.3 Extinction 117 6.3.4 Derivation of Tea and Lboi 120 6.3.5 X-ray Properties 121 6.4 Circumstellar Disks 122 6.4.1 Signatures of Disks 122 6.4.2 Disk Frequency and Lifetimes 124 8 TABLE OF CONTENTS — Continued 6.5 The IC 348 Stellar Population 125 6.5.1 Cluster Membership 125 6.5.2 H-R Diagram 126 6.5.3 Dynamics 127 6.5.4 Star Formation History 129 6.5.5 The Initial Mass Function 131 6.6 Conclusions 139 6.7 Notes on IR Spectral Classification 141 6.7.1 GO and Earlier 142 6.7.2 GO to Early K 143 6.7.3 Late K 143 6.7.4 Early M 144 6.7.5 Mid M 145 6.7.6 Late M and Other Types 146 6.8 Notes on Optical Classification 148 7 p Ophiuchi 171 7.1 Observations 174 7.2 Individual Source Characteristics 175 7.2.1 IR Spectral Classification 175 7.2.2 Derivation of Aj, Teff, and Lboi 179 7.3 The p Oph Stellar Population 181 7.3.1 Cluster Membership 181 7.3.2 Global Properties of the IR Spectra and Colors 182 7.3.3 The H-R Diagram and Star Formation History 184 7.3.4 The Initial Mass Function 186 7.4 Conclusions 193 7.5 Notes on Individual Sources 195 TABLE OF CONTENTS — Continued 8 Future Work References 10 LIST OF FIGURES 2.1 Theoretical tracks tested against CM Dra and YY Gem 22 2.2 Theoretical tracks tested against the Pleiades 23 3.1 High-resolution Li I spectrum of V410 X-ray 3 33 3.2 Low-resolution optical spectrum of V410 X-ray 3 34 3.3 AT-band spectrum of V410 X-ray 3 35 3.4 H-R diagram for V410 X-ray 3 36 4.1 Low-resolution optical spectrum of p Oph 162349.8 - 242601 47 4.2 H-R diagram for p Oph 162349.8 — 242601 48 5.1 A'-band spectra of sources in L1495E 91 5.2 Finding chart for the A'-band image of L1495E 92 5.3 Recent temperature scales for cool stars 93 5.4 H - K vs. J — H for L1495E 94 5.5 H-R diagram for L1495E 95 5.6 IMF for L1495E 96 5.7 A'-band luminosity function for L1495E 97 5.8 Equivalent widths of A'-band lines 98 5.9 A'-band spectra of KOV stars 99 5.10 A'-band spectra of KlV stars 100 5.11 A'-band spectra of K7V stars 101 5.12 AT-band spectra of MlV stars 102 5.13 A'-band spectra of M2V stars 103 5.14 A'-band spectra of M3V stars 104 5.15 Composite standard spectra for A'-band classification 105 11 LIST OF FIGURES — Continued 5.16 Composite standard spectra for A'-band classification 106 6.1 i^-band spectra of sources in IC 348 154 6.2 K-hsind spectra of sources in IC 348 155 6.3 A'-band spectra of sources in IC 348 156 6.4 A'-band spectra of sources in IC 348 157 6.5 Low-resolution optical spectra of M6 sources in IC 348 158 6.6 Low-resolution optical spectra of M7-M8 sources in IC 348 159 6.7 H-R diagram for IC 348 with DM94 160 6.8 H-R diagram for IC 348 with DM97 161 6.9 H — K vs.