Discovering and Characterizing Embedded Stellar Clusters in the Near-Infrared Item Type text; Electronic Dissertation Authors Leistra, Andrea 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 28/09/2021 19:31:15 Link to Item http://hdl.handle.net/10150/193801 DISCOVERING AND CHARACTERIZING EMBEDDED STELLAR CLUSTERS IN THE NEAR-INFRARED by Andrea Lynn Leistra 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 dissertation prepared by Andrea Lynn Leistra entitled “Discovering and Charac- terizing Embedded Stellar Clusters in the Near-Infrared” and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy. Date: July 10, 2006 James Liebert Date: July 10, 2006 Philip Massey Date: July 10, 2006 George Rieke Date: July 10, 2006 Erick Young 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: July 10, 2006 Dissertation Director: James Liebert 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: Andrea Lynn Leistra 4 ACKNOWLEDGMENTS First, special thanks to my advisor, Jim Liebert. I've learned a great deal from Jim, and I'm always amazed at how much he knows, even outside his main ar- eas of research. Thanks also to my main collaborators, Angela Cotera and Phil Massey, for invaluable scientific insight and help with how to be a good scientist. Second, thanks to the astronomers whose instruments and telescope access made my research possible: Don McCarthy for the use of PISCES and Michael Burton for agreeing to collaborate to allow me to use the Anglo-Australian Telescope. Chris Tinney's instrument support for IRIS2 was invaluable. Thanks to all the astronomers whose comments helped make this thesis stronger, especially Margaret Hanson, Mike Meyer, and the referees for the papers that ap- pear as Chapters 2 and 3. Thanks to the current and former grad students of Steward Observatory who helped with computer and science issues, as well with keeping my sanity in- tact, especially Jeremy Bailin, Kris Eriksen, Craig Kulesa, Chris Groppi, Jackie Monkiewicz, and Jane Rigby. Many thanks to the Steward people who make everything work: Erin Carlson, Michelle Cournoyer, Catalina Diaz-Silva, Joy Facio, Jeff Fookson, and Neal Lau- ver. Thanks also to all the telescope operators at the 90”, the MMT, and the AAT for keeping things running smoothly and fixing them when they didn't. And finally, thanks to everyone who encouraged my interest in science in general and astronomy in particular before I ever got here. Most especially my parents, but also the great teachers I've had over the years from grade school through col- lege. They may never see this thesis but it wouldn't have been written without them. 5 DEDICATION For my partner, Jane Rigby, who kept me going. 6 TABLE OF CONTENTS LIST OF FIGURES . 8 LIST OF TABLES . 11 ABSTRACT . 13 CHAPTER 1 INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : 15 CHAPTER 2 DISCOVERING INFRARED EMBEDDED CLUSTERS WITH 2MASS 24 2.1 Introduction . 24 2.2 Searching the 2MASS Catalog . 26 2.2.1 Algorithm . 26 2.2.2 Targeted Search . 27 2.2.3 Full-Sky Search . 28 2.3 Analysis . 35 2.3.1 False Cluster Detections . 35 2.3.2 Missed Clusters & Completeness of the Sample . 36 2.3.3 Embedded Cluster Candidates . 41 2.4 Limitations of Automated Searches and Implications for Future Studies . 43 2.5 Followup Observations of Cluster Candidates: False Detections . 45 2.5.1 DB11 Cluster Candidate . 46 2.5.2 DB41 Cluster Candidate . 52 2.6 Finding Embedded Clusters: Conclusions . 56 CHAPTER 3 SOUTHERN 2MASS-SELECTED YOUNG STELLAR CLUSTERS: PHOTOMETRY, SPECTROSCOPY, AND THE INITIAL MASS FUNCTION : : 57 3.1 INTRODUCTION . 57 3.2 OBSERVATIONS & DATA REDUCTION . 60 3.3 Analysis . 64 3.3.1 Spectroscopy . 64 3.3.2 Photometry . 79 3.4 The K Band Luminosity Function and the Initial Mass Function . 95 3.4.1 The G305.3+0.2 Cluster . 97 3.4.2 The KLF for the G353.4-0.36 cluster . 106 3.5 Summary . 108 CHAPTER 4 NORTHERN 2MASS-SELECTED YOUNG STELLAR CLUSTERS: PHOTOMETRY AND THE INITIAL MASS FUNCTION : : : : : : : : : : : : 110 4.1 INTRODUCTION . 110 4.2 OBSERVATIONS & DATA REDUCTION . 112 7 TABLE OF CONTENTS — Continued 4.3 Analysis . 114 4.3.1 Sh 2-217 Cluster . 114 4.3.2 IRAS 06058+2158 Cluster . 125 4.3.3 IRAS 06104+1524 Cluster . 128 4.3.4 Sh 2-288 . 136 4.3.5 Comparison of Methods for IMF Determination . 138 4.4 Summary . 142 CHAPTER 5 CONCLUSIONS AND FUTURE DIRECTIONS : : : : : : : : : : : 145 5.1 The Initial Mass Function of Embedded Stellar Clusters . 145 5.2 Discovering Embedded Stellar Clusters using 2MASS: Complete- ness and Distribution . 149 REFERENCES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 153 8 LIST OF FIGURES 2.1 2MASS Ks image of an “extinction hole” detected as a cluster can- didate by the automated search. 37 2.2 2MASS Ks image of a sparse-field overdensity detected as a cluster by the automated search . 38 2.3 2MASS Ks image of a galaxy detected as a cluster candidate by the automated search. 39 2.4 Distribution of embedded cluster candidates in galactic coordinates. 42 2.5 Major axis (in arcmin) of cluster candidates as determined from 2MASS images. 44 2.6 80×80 K-band image of the DB11 cluster candidate from IRIS2/AAT. 47 2.7 80×80 K-band image of the DB41 cluster candidate from IRIS2/AAT. 48 2.8 All sources detected in the “field region” for the DB11 cluster can- didate. 49 2.9 All sources detected in the “cluster region” for the DB11 cluster candidate. 50 2.10 Statistically-corrected “cluster region” sources for the DB11 cluster candidate. 51 2.11 All sources detected in the “field region” for the DB41 cluster can- didate. 53 2.12 All sources detected in the “field region” for the DB41 cluster can- didate. 54 2.13 Statistically-corrected “cluster region” sources for the DB41 cluster candidate. 55 3.1 JHK image of the G305+00.2 cluster. 62 3.2 JHK image of the G353.4-0.2 cluster. 63 3.3 Spectra for the cluster stars in the G305.3+0.2 cluster. 67 3.4 Spectroscopically classified sources marked on the G305.3+0.2 clus- ter. 68 3.5 K-band image of the G305.3+0.2 cluster region with 8 µm contours from the MSX mission. 70 3.6 Spectra for sources in the G353.4-0.36 cluster. 75 3.7 Maser positions from the literature overlaid on the G353.4-0.36 clus- ter K-band image. 76 3.8 Nebular spectrum from the G353.4-0.36 cluster region. 77 3.9 K vs H-K for the G305.3+0.2 cluster region. 88 LIST OF FIGURES — CONTINUED 9 3.10 K vs H-K for a randomly selected control field for G305.3+0.2, with the same area as the cluster field. 89 3.11 Corrected K vs. H-K for the G305.3+0.2 cluster region with ZAMS overplotted. 91 3.12 Corrected J − H vs. H − K for the G305.3+0.2 cluster region. 93 3.13 K vs H-K for the G353.4-0.36 cluster region. 96 3.14 Completeness fraction determined by artificial-star tests for the G305.3+0.2 cluster region. 98 3.15 K-band luminosity functions for G305.3+0.2 cluster (solid) and field (dashed), normalized to the same total number of stars. 99 3.16 Completeness-corrected K-band luminosity function for G305.3+0.2 cluster. 100 3.17 The completeness-corrected IMF for the G305.3+0.2 cluster. 104 3.18 The raw (solid line) and completeness-corrected (dashed line) KLF for the G353.4-0.36 cluster. 107 4.1 K-band image of the Sh 2-217 cluster center (North=up, East=left). 115 4.2 K vs. H − K color-magnitude diagram for the cluster near Sh2-217. 118 4.3 Statistically-corrected K vs. H − K color-magnitude diagram for the cluster near Sh2-217. 119 4.4 K luminosity function for the Sh2-217 cluster. 120 4.5 K vs.