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Lanz Gsas.Harvard 0084L 11129 Constraining the Evolution of Galaxies over the Interaction Sequence with Multiwavelength Observations and Simulations The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Lanz, Lauranne. 2013. Constraining the Evolution of Galaxies over the Interaction Sequence with Multiwavelength Observations and Simulations. Doctoral dissertation, Harvard University. Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:11181230 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA Constraining the Evolution of Galaxies over the Interaction Sequence with Multiwavelength Observations and Simulations A dissertation presented by Lauranne Lanz to The Department of Astronomy in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of Astronomy & Astrophysics Harvard University Cambridge, Massachusetts August 2013 c 2013 | Lauranne Lanz All rights reserved. Dissertation Advisor: Doctor Howard A. Smith Lauranne Lanz Constraining the Evolution of Galaxies over the Interaction Sequence with Multiwavelength Observations and Simulations Abstract Interactions are crucial for galaxy formation and profoundly affect their evolution. However, our understanding of the impact of interactions on star formation and activity of the central supermassive black hole remains incomplete. In the canonical picture of the interaction process, these processes are expected to undergo a strong enhancement, but some recent studies have not found this prediction to be true in a statistically meaningful sense. This thesis uses a sample of local interactions observed from the ultraviolet to the far-infrared and a suite of N-body hydrodynamic simulations of interactions to examine the evolution of star formation, stellar mass, dust properties, and spectral energy distributions (SEDs) over the interaction sequence. First, we present the SEDs of 31 interactions in 14 systems, which we fit with stellar population synthesis models combined with a thermal dust model. We examine the differences between mildly, moderately, and strongly interacting systems. The star formation rate (SFR), dust luminosity, and the 15-25 K dust component temperature increase as the interaction progresses from moderately to strongly interacting. However, the SFR per stellar mass remains constant across the interaction stages. Second, we create 14 hydrodynamic simulations of isolated and interacting galaxies and calculate simulated photometry in 25 bands using the sunrise radiative transfer iii code. By comparing observed and simulated SEDs, we identify the simulation properties necessary to reproduce an interaction's SED. The best matches originate from simulated systems of similar stellar mass, infrared luminosities, dust mass, and SFR to the observed systems. Although an SED alone is insufficient to identify the interaction stage, strongly interacting systems preferentially match SEDs from times close to coalescence in the simulations. Third, we describe a case study of a post-merger system, Fornax A, for which we constrain its parameters of its progenitors. Based on the excess dust mass in this elliptical 10 galaxy, we estimate a spiral galaxy with a stellar mass of (1 − 6) × 10 M brought in ≈10% of Fornax A's current stellar mass. We describe the probable two-outburst history that created the radio lobes ∼0.4 Gyr ago and two cavities in the X-ray emission closer to the nucleus ∼0.1 Gyr ago. iv Contents Abstract iii Acknowledgments ix Dedication xii 1 Introduction 1 1.1 What Happens in a Galaxy Interaction? . .3 1.2 A Golden Age for the Study of Galaxy Interactions . .8 1.2.1 A Wealth of Multiwavelength Observations . .8 1.2.2 Computational Tools . 11 1.3 Approaches to Studying Galaxy Interactions . 13 1.3.1 Observations of Interactions . 13 1.3.2 Comparison between Observations and Simulations . 14 1.3.3 Archeology Conducted on Post-Mergers . 15 2 Global Star Formation Rates and Dust Emission Over the Galaxy In- teraction Sequence 18 2.1 Introduction . 19 2.2 The Spitzer Interacting Galaxy Survey (SIGS) Sample . 24 2.2.1 Sample Description . 24 2.2.2 Estimating the Interaction Phase . 28 v CONTENTS 2.2.3 Comparison Non-interacting Sample . 29 2.3 Observations and Data Reduction . 30 2.3.1 Galaxy Distances . 37 2.3.2 Infrared Photometry . 37 2.3.3 Ultraviolet Photometry . 44 2.3.4 Aperture and Uncertainty Determination . 48 2.4 SED Fitting with MAGPHYS . 55 2.4.1 Fitting Process . 55 2.4.2 SED Fits . 56 2.5 Discussion . 70 2.5.1 Variation in SED Shape with Interaction Stage . 70 2.5.2 Variations in Galaxy Parameters with Interaction Stage . 74 2.5.3 Relative Importance of Specific Data Sets in Constraining Galaxy Parameters . 82 2.5.4 Comparison of the SFR Derived from the SED to Monochromatic and Broad-band Relations . 86 2.6 Summary . 89 3 Simulated Galaxy Interactions as Probes of Merger Spectral Energy Distributions 101 3.1 Introduction . 102 3.2 Observations . 106 3.2.1 Sample Selection . 106 3.2.2 Photometry . 108 3.2.3 Interaction Stage Classification . 109 3.2.4 Deriving Galaxy Properties of the Observed Systems . 109 3.3 Simulations . 110 3.3.1 Hydrodynamical Simulations . 111 vi CONTENTS 3.3.2 Radiative Transfer . 114 3.4 Methodology . 118 3.4.1 Matching Criterion . 118 3.4.2 Selection of the Best and Worst Matches . 120 3.5 Discussion . 126 3.5.1 Where Do the Best Matched SEDs Come From? . 126 3.5.2 Recovery of Galaxy Properties . 137 3.5.3 Effectiveness of Morphology-based Stages Estimates of Interaction . 142 3.5.4 Evolution of SEDs in Major Mergers . 146 3.6 Conclusions . 146 4 Constraining the Outburst Properties of the SMBH in Fornax A through X-ray, Infrared, and Radio Observations 150 4.1 Introduction . 152 4.2 Observations and Data Reduction . 154 4.2.1 Spitzer Observations . 154 4.2.2 Chandra Observations . 158 4.2.3 XMM-Newton Observations . 158 4.2.4 Radio, Optical, and CO Observations . 158 4.3 Data Analysis . 159 4.3.1 Spitzer Analysis . 159 4.3.2 Chandra Analysis . 162 4.3.3 XMM-Newton Analysis . 162 4.4 Multiwavelength Comparison of Features . 166 4.4.1 Nuclear Emission . 166 4.4.2 Inner Jet . 170 4.4.3 Extended Non-Stellar Emission . 173 vii CONTENTS 4.5 Multiwavelength View of the Consequences of the Merger Event . 177 4.5.1 Dust Distribution . 177 4.5.2 Dust Mass and Merger Progenitor Mass . 181 4.5.3 Outburst Ages . 183 4.5.4 Outburst Energies . 185 4.5.5 Comparison of the Cen A and Fornax A Jets . 186 4.6 Conclusions . 187 5 Future Directions 190 5.1 Expanding the Interaction Sample . 190 5.2 Examining Morphology . 192 5.3 Studying AGN Activity . 194 References 195 viii Acknowledgments Before we dive into the wondrous dance of interacting galaxies, I want to thank the many people without whom this dissertation and the long process before it would not have been possible. First and foremost, I thank my wonderful parents. Maman, you have been such an amazing support and friend. You have given me guidance, strength, laughs, hugs, and great conversations. Dad, I still remember going to that first big telescope at L'Observatoire de Haute Provence with you and your advice has helped guide me since. My siblings, Alexis and Shakoo, I thank you for listening patiently when I ramble about my passions and I hope that I have let you ramble about yours. Merci `atoute ma famille pour vos bons voeux et l'amour qui m'a soutenue surtout ces derniers jours quand je finissais ma th`ese. I have had several wonderful advisors, who have shaped me as a scientist. I thank, my advisor Howard Smith for developing such a wonderful thesis project with me and for recognizing and encouraging my love of outreach. I thank John Huchra for luring me into the study of galaxies my first semester at Harvard, and Christine Jones and Bill Forman for nurturing that delight, introducing me to X-ray astronomy, and, letting me discover infrared astronomy. I thank Matt Ashby for his steadfast support and assistance, and for taking me on my first observing trip in Chile. I also thank Lee Mundy, Sidney Wolff, and Steve Strom, who introduced me to astronomical research and convinced me it was much better than particle physics. I thank Andreas Zezas for many reasons: for his many thoughtful comments, for ix CHAPTER 0. ACKNOWLEDGMENTS helpful and insightful scientific conversations, and for helping to shape my thesis. I thank Chris Hayward, without whose simulations I would not have been able to complete a substantive part of this thesis, Ryan Hickox who taught me so much IDL and was very patient with a young graduate student, Elisabete da Cunha who helped understand MAGPHYS and worked with me to modify it to my needs, Volker Tolls who taught the love/hate relation one has with HIPE, Patrik Jonsson who taught me how to work with sunrise outputs, Paul Nulsen for our conversations, and Ralph Kraft for his helpful explanations of jet and AGN processes. I thank Giovanni Fazio, Steve Willner, Joe Hora, and Zhong Wang for welcoming me into the IRAC group. I thank Sarah Willis, Rafael Martinez Galarza, Andres Guzman, Dharam Vir Lal, Zhiyuan Li, Ryan Johnson, and Felipe Santos for fruitful collaborations and friendly group meetings. I am grateful to my thesis (advisory) committee for their helpful advice. I thank Alyssa Goodman for her insights regarding the dangers of χ2 fitting and Lars Hernquist for bringing a theorist's perspective and welcoming me to his group meeting.
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