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The History of Enrichment of the Intergalactic Medium Using Cosmological Simulations

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The History of Enrichment of the Intergalactic Medium Using Cosmological Simulations Item Type text; Electronic Dissertation Authors Oppenheimer, Benjamin Darwin 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 03/10/2021 02:22:25 Link to Item http://hdl.handle.net/10150/194237 THE HISTORY OF ENRICHMENT OF THE INTERGALACTIC MEDIUM USING COSMOLOGICAL SIMULATIONS by Benjamin Darwin Oppenheimer 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 8 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Benjamin Darwin Oppenheimer entitled “The History of Enrichment of the Intergalactic Medium Using Cosmological Simulations” and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy. Date: August 6, 2008 Romeel Dave´ Date: August 6, 2008 Chris Impey Date: August 6, 2008 Jill Bechtold Date: August 6, 2008 Buell Jannuzi Date: August 6, 2008 John Bieging 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: August 6, 2008 Dissertation Director: Romeel Dave´ 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: Benjamin Darwin Oppenheimer 4 ACKNOWLEDGMENTS I first would like to thank my adviser Romeel Dave´ for monetary support, an always open door for advice and guidance, summering in Europe, and the insistence of writing four papers for my thesis. I also must thank John Bieging for being a great adviser for my second-year project. As the first student of Mike Meyer, I also thank him for a positive advising experience. While on the subject, I feel I have to go out of my way to thank the faculty of Steward, who accepted me twice (barely I'm sure), and with whom I always had positive experiences. Special thanks to Jim Liebert. I must mention my committee, who were especially willing to go out of their way to read such a dense thesis. Of course I have to thank Michelle Cournoyer, who was always on top of the administrative stuff, which I am incapable of doing. Also of notable assistance were Catalina Diaz-Silva, Carmen Henley, Sharon Jones, and Neal Lauver. I do not have room to list the many collaborators and contributors to this science, so I forward those for now to the acknowledgments in the individual published papers. As for friends and fellow grad students, I will only show a list here as I will thank them more in a limited edition version. They include officemates: Desika Narayanan, Brandon Kelly, Shane Bussman, Dave Sudarsky, Tammy Rodgers, Audra Baleisis, Beth Biller, Paula White, Greg Rudnick, and of course Christian Ott. In addition those who made my grad school experience special and unique are Casey Meakin, Andy Marble, John Trump, Aleks Diamond-Stanek, Iva Mom- cheva, Luc Dessart, Dave Sand, Chris Groppi, Andy Skemer, Brandon Swift, Stephane Herbert-Fort, Stephanie Cortes, Murray Silverstone, Matt Kenworthy, Tim Pickering, and how could I forget Eric Mamajek (I tried to). Of course I could not have finished my thesis without Kristian Finlator, whose intimate knowledge of the literature and willingness for discussions whenever were invaluable. An incomplete list of influential people from worlds other than astronomy include Ingrid Daubar, Joe Spitale, Krista Nunn, Dave O'Brien, Brooke White, Beena Chandy, Mike Wyner, Ojas Tejani, and Stephanie Hawley. I began my journey in astronomy as a summer student at the AAVSO, and for- ever am indebted to Janet Mattei to whom I dedicate this thesis. She always be- lieved in me in whatever goal I set for myself, whether it was observational vari- able star astronomy, developing software for an internet company, or even the- oretical cosmology. Special thanks go out to Don McCarthy (astronomy camp), Dave Latham (junior thesis), and Elizabeth O. Waagen (also AAVSO). Of course I have to thank my parents Annette and Dick for allowing me to pursue my unusual career choice, plus my sister Emily for reminding me how much of a dork I am. And of course, this thesis would not have been possible without my love Lisa, who really bore the brunt of my thesis Dementia when I had to write over half of the material in the last three months while I neglected every other aspect of my life. 5 DEDICATION In memory of Janet Mattei 6 TABLE OF CONTENTS LIST OF FIGURES . 9 LIST OF TABLES . 11 ABSTRACT . 12 1 INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 14 1.1 IGM Metal-Line Observations . 15 1.2 IGM Metal-Line Simulations . 18 1.3 The Goal: A Consensus Between Simulation and Observation . 25 1.4 Thesis Layout . 28 2 COSMOLOGICAL SIMULATIONS OF INTERGALACTIC MEDIUM ENRICH- MENT FROM GALACTIC OUTFLOWS : : : : : : : : : : : : : : : : : : : : : 30 2.1 Introduction . 30 2.2 Simulations . 33 2.2.1 Hydrodynamic Simulations of Structure Formation . 33 2.2.2 Radiative Cooling With Metal Lines . 35 2.2.3 Superwind Feedback . 38 2.2.4 Runs and Outflow Models . 43 2.2.5 Spectral Generation . 45 2.2.6 UV Background . 49 2.3 Global Physical Properties . 51 2.3.1 Star Formation Rate Density . 51 2.3.2 Outflow Properties . 53 2.3.3 IGM Enrichment and Heating . 56 2.4 Physical Properties of Metals and C IV Absorbers . 60 2.4.1 Evolution of Metals in the IGM . 60 2.4.2 C IV Absorption in Phase Space . 65 2.4.3 Metallicity-Density Relationship . 71 2.4.4 Evolution of Median C IV Absorber in Phase Space . 76 2.5 Testing Outflow Models Against Observations . 78 2.5.1 C IV Mass Density . 78 2.5.2 C IV Line Parameters . 85 2.5.3 Pixel Optical Depth Statistics . 92 2.6 Numerical Resolution . 98 2.7 Conclusions . 103 3 MASS, METAL, AND ENERGY FEEDBACK IN COSMOLOGICAL SIMULA- TIONS : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 110 3.1 Introduction . 110 7 3.2 Simulations . 115 3.2.1 Metal Yields . 118 3.2.2 Group Finder . 125 3.2.3 Wind Model Modifications . 129 3.3 The Universal Energy Balance . 135 3.4 The Universal Metal Budget . 138 3.4.1 Sources of Metals . 138 3.4.2 The Location of Metals . 146 3.5 Galaxies and Feedback . 154 3.5.1 Feedback as a Function of Galaxy Mass . 155 3.5.2 Feedback by Volume . 160 3.5.3 Wind Recycling . 163 3.5.4 Wind Recycling Timescales . 168 3.6 Summary . 179 4 THE NATURE AND ORIGIN OF LOW-REDSHIFT O VI ABSORBERS : : : : : 185 4.1 Introduction . 185 4.2 Simulations . 189 4.2.1 Model Runs . 189 4.2.2 Post-Run Physics Variations . 194 4.3 Comparison of Simulated and Observed O VI Absorbers . 199 4.3.1 H I Observables . 201 4.3.2 O VI Observables . 206 4.4 Physical Conditions of O VI Absorbers . 221 4.4.1 A Photo-ionized Model for O VI Absorbers . 222 4.4.2 Cooling Times . 226 4.4.3 Alignment with H I . 228 4.4.4 Turbulence in the IGM . 241 4.5 Origin and Environment of O VI . 248 4.5.1 Ages of O VI Absorbers . 250 4.5.2 Galaxy Environments of O VI Absorbers . 252 4.5.3 Collisionally Ionized O VI . 255 4.5.4 COS Simulated Observations and Environment . 260 4.6 Summary . 266 5 HIGH REDSHIFT METAL ABSORBER PREDICTIONS FROM COSMOLOGICAL SIMULATIONS : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 272 5.1 Introduction . 272 5.2 Simulations . 275 5.3 Physical Properties . 278 5.3.1 Galaxy Mass Function . 278 5.3.2 Star Formation . 282 8 5.3.3 Winds . 283 5.3.4 Metallicity Distribution . 285 5.4 Ionization Backgrounds . 289 5.4.1 Ionization Cases . 289 5.4.2 Ionization Behavior . 294 5.5 Observational Predictions . 299 5.5.1 Column Density Distributions . 300 5.5.2 Metal Mass and Ion Densities . 304 5.5.3 Equivalent Width Distributions . 314 5.5.4 Aligned Absorber Ratios . 317 5.6 Physical and Environmental Interpretation . 322 5.6.1 Physical Conditions . 323 5.6.2 Origin of IGM Metals . 326 5.6.3 The Galaxy-Absorber Connection at High Redshift . 329 5.6.4 Low Ionization Species . 333 5.6.5 Evolution to z = 8 . 335 5.7 Summary . 337 6 CONCLUSIONS AND FUTURE DIRECTION : : : : : : : : : : : : : : : : : : 342 REFERENCES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 356 9 LIST OF FIGURES 2.1 Simulated spectra . 48 2.2 Lyman-alpha flux decrement plot .
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  • The Search for the Missing Baryons at Low Redshift

    The Search for the Missing Baryons at Low Redshift

    Bregman 1 The Search for the Missing Baryons at Low Redshift Joel N. Bregman Department of Astronomy, University of Michigan Key Words astrophysics, cosmology, intergalactic medium Abstract The baryon content of the universe is known from Big Bang nucleosynthesis and cosmic microwave background considerations, yet at low redshift, only about one-tenth of these baryons lie in galaxies or the hot gas seen in galaxy clusters and groups. Models posit that these “missing baryons” are in gaseous form in overdense filaments that connect the much denser virialized groups and clusters. About 30% of the baryons are cool (<105 K) and are detected in Lyα absorption studies, but about half the mass is predicted to lie in the 105-107 K regime, where detection is very challenging. Material has been detected in the 2-5×105 K range through OVI absorption studies, indicating that this gas accounts for about 7% of the baryons. Hotter gas (0.5-2×106 K) has been detected at zero redshift by OVII and OVIII Kα absorption at X-ray energies. However, this appears to be correlated with the Galactic soft X-ray background, so it is probably Galactic Halo gas, rather than a cosmologically significant Local Group medium. There are no compelling detections of the intergalactic hot gas (0.5-10×106 K) either in absorption or in emission. Early claims of intergalactic X-ray absorption lines have not been confirmed, but this is consistent with theoretical models, which predited equivalent widths below current detection thresholds. There have been many investigations for emission from this gas, within and beyond the virial radius of clusters, but the positive signals for this soft emission are largely artifacts of background subtraction and field-flattening.