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The Effects of Galaxy Interactions on Star Formation

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The Effects of Galaxy Interactions on Star Formation Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2011 The effects of galaxy interactions on star formation Bradley W. Peterson Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Physics Commons Recommended Citation Peterson, Bradley W., "The effects of galaxy interactions on star formation" (2011). Graduate Theses and Dissertations. 10180. https://lib.dr.iastate.edu/etd/10180 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. The effects of galaxy interactions on star formation by Bradley Wayne Peterson A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Astrophysics Program of Study Committee: Curtis Struck, Major Professor Charles Kerton Lee Anne Willson Craig Ogilvie Diane Cook Iowa State University Ames, Iowa 2011 Copyright c Bradley Wayne Peterson, 2011. All rights reserved. ii TABLE OF CONTENTS LIST OF TABLES . vi LIST OF FIGURES . vii ACKNOWLEDGEMENTS . x ABSTRACT . xi CHAPTER 1. Introduction . 1 1.1 Galaxy Interactions . 1 1.2 Induced Star Formation . 3 1.3 Physics of Star Formation . 5 1.3.1 Star Formation on Small Scales . 6 1.3.2 Star Formation on Galaxy Scales . 9 1.4 Deciphering Star Formation Histories . 19 1.4.1 Evolutionary Synthesis Models . 19 1.4.2 Super Star Clusters . 22 1.5 Suppression of star formation . 29 1.5.1 Temporary suppression . 29 1.5.2 Ram pressure stripping . 30 1.6 Summary . 32 1.7 Dissertation Organization . 33 CHAPTER 2. Star Clusters in the Interacting Galaxy System Arp 284 . 34 2.1 Abstract . 34 2.2 Introduction . 35 iii 2.3 ............................................. 37 2.3.1 Nucleus of NGC 7714 . 38 2.3.2 Stellar Ring of NGC 7714 (Feature 1) . 38 2.3.3 Southern Tails of NGC 7714 (Features 2 and 3) . 39 2.3.4 Northern Tail of NGC 7714 (Feature 4) . 39 2.3.5 Bridge (Feature 5) . 40 2.3.6 Nucleus of NGC 7715 . 40 2.3.7 Eastern Tail of NGC 7715 (Feature 6) . 41 2.4 Observations . 41 2.4.1 HST observations . 41 2.4.2 H ii region observations . 42 2.5 HST Data Analysis . 44 2.5.1 Data Reduction . 44 2.5.2 Cluster Selection . 44 2.5.3 Photometry of clusters . 45 2.5.4 H ii region photometry . 46 2.6 HST Results . 47 2.6.1 Cluster colors . 47 2.6.2 Age determination . 49 2.6.3 Luminosity function . 55 2.7 Discussion . 56 2.7.1 HST cluster ages . 56 2.7.2 HST cluster mass function . 58 2.7.3 H ii region age estimates . 61 2.7.4 Spitzer colors . 63 2.7.5 Comparison with Chandra .......................... 69 2.8 Conclusions . 71 iv CHAPTER 3. The star cluster population of the interacting system Arp 261 73 3.1 Introduction . 73 3.2 Observations . 74 3.2.1 HST ...................................... 74 3.2.2 Spitzer ..................................... 75 3.2.3 GALEX .................................... 76 3.3 Data Analysis . 76 3.3.1 HST Photometry . 76 3.3.2 Spitzer and GALEX photometry . 80 3.3.3 Age estimates . 80 3.4 Results . 81 3.4.1 Cluster age distribution . 81 3.4.2 Cluster luminosity function . 86 3.4.3 Cluster mass function . 87 3.4.4 Large aperture ages . 88 3.5 Discussion . 90 3.5.1 Collision scenarios . 90 3.5.2 Cluster age distribution in different regions . 93 3.5.3 Clump ages vs. cluster ages . 96 3.5.4 Spitzer colors . 98 3.6 Summary & Conclusions . 102 CHAPTER 4. Detection of Powerful Mid-IR H2 Emission in the Bridge Between the Taffy Galaxies . 104 4.1 Abstract . 104 4.2 Introduction . 105 4.3 Observations and Data Reduction . 107 4.3.1 IRS spectra . 107 4.3.2 IRAC and MIPS images . 110 v 4.4 Results . 110 4.4.1 Spectra . 110 4.4.2 H2 distribution . 115 4.4.3 Excitation diagram and H2 mass surface densities . 118 4.5 Discussion . 122 4.5.1 H2 heating sources . 122 4.5.2 Comparison with CO data . 133 4.6 Summary and Future Work . 133 CHAPTER 5. SUMMARY AND DISCUSSION . 135 5.1 Super star clusters . 135 5.1.1 Summary and discussion . 135 5.1.2 Future work . 136 5.2 Star formation suppression . 137 5.2.1 Summary and discussion . 137 5.2.2 Future work . 138 5.3 Final remarks . 140 APPENDIX A. Additional data tables for Arp 284 . 141 APPENDIX B. Complete cluster data tables for Arp 261 . 154 APPENDIX C. Data tables for Taffy galaxies . 187 BIBLIOGRAPHY . 191 vi LIST OF TABLES Table 2.1 HST imaging of Arp 284 . 42 Table 2.2 Clusters by age bin for Z = 0:2Z ..................... 61 Table 3.1 HST imaging of Arp 261 . 75 Table A.1 Cluster magnitudes and age estimates . 141 Table A.2 Cluster E(B − V ) and mass estimates . 146 Table A.3 H ii region photometry . 151 Table A.4 H ii region ages . 152 Table A.5 H ii region extinctions . 153 Table B.1 Cluster magnitudes and EW(Hα) . 154 Table B.2 Cluster age estimates . 170 Table.
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