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The Pennsylvania State University The Graduate School The Eberly College of Science POPULATION SYNTHESIS AND ITS CONNECTION TO ASTRONOMICAL OBSERVABLES A Thesis in Astronomy and Astrophysics Michael S. Sipior c 2003 Michael S. Sipior Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2003 We approve the thesis of Michael S. Sipior Date of Signature Michael Eracleous Assistant Professor of Astronomy and Astrophysics Thesis Advisor Chair of Committee Steinn Sigurdsson Assistant Professor of Astronomy and Astrophysics Gordon P. Garmire Evan Pugh Professor of Astronomy and Astrophysics W. Niel Brandt Associate Professor of Astronomy and Astrophysics L. Samuel Finn Professor of Physics Peter I. M´esz´aros Distinguished Professor of Astronomy and Astrophysics Head of the Department of Astronomy and Astrophysics Abstract In this thesis, I present a model used for binary population synthesis, and 8 use it to simulate a starburst of 2 10 M over a duration of 20 Myr. This × population reaches a maximum 2{10 keV luminosity of 4 1040 erg s−1, ∼ × attained at the end of the star formation episode, and sustained for a pe- riod of several hundreds of Myr by succeeding populations of XRBs with lighter companion stars. An important property of these results is the min- imal dependence on poorly-constrained values of the initial mass function (IMF) and the average mass ratio between accreting and donating stars in XRBs. The peak X-ray luminosity is shown to be consistent with recent observationally-motivated correlations between the star formation rate and total hard (2{10 keV) X-ray luminosity. Recent calculations published by other groups fail to account for the aforementioned sustained high X-ray luminosity from different mass companions. Model cumulative luminosity functions show increasing steepness at the high end, as the most luminous systems die off. I also consider those XRBs with massive companions that survive the second supernova, and go on to become double compact object binaries. Depending upon the initial configuration at the time the second compact object is formed, the system may go on to experience a merger through iii the loss of orbital energy to gravitational radiation. We show that with a detection threshold of h 10−21 for gravitational radiation (comparable to ∼ the expected sensitivity of LIGO I), a total merger rate of 6 10−3{10−2 yr−1 × can be expected. This means that detection of gravitational wave sources through this formation channel will have to wait for LIGO II, with an order of magnitude improvement in sensitivity, and a commensurate thousand-fold increase in search volume and event rates. In an attempt to compare model predictions with observations, I analyze a sample of 41 nearby mildly-active galaxies observed in a snapshot survey during Cycles 1 and 2 of the Chandra X-ray Observatory. Using the observed X-ray images, 33 nuclei are detected, and diffuse nuclear X-ray emission is found in 25% of the targets. Substantial XRB populations are detected in all but a few fields, many with luminosities in excess of 1039 erg s−1. Over four hundred sources were detected overall, with fourteen in the latter high luminosity category. All but one of these sources is found in a spiral host galaxy, implying that such sources are generally tied to higher star formation rates. iv Contents List of Figures vii List of Tables x 1 Introduction 1 1.1 Historical Perspective . 1 1.2 The Physics of Binary Evolution . 10 1.2.1 Gravitational Waves . 12 1.3 Overview . 15 2 Simulating the X-ray luminosity evolution of a stellar pop- ulation 18 2.1 Introduction . 18 2.1.1 X-ray binaries revealed by Chandra . 18 2.1.2 Observables for reconstructing a star formation history 19 2.2 Population modeling . 22 2.2.1 History and authorship of the population synthesis code 22 2.2.2 Population code theory of operation, choice and extent of parameter space . 23 2.2.3 Implementation of mass transfer in the code . 31 v 2.2.4 Mass accretion and resulting X-ray luminosity . 37 2.3 Simulation results . 44 2.4 Comparison with other theoretical work . 69 2.4.1 Numerical simulations by Van Bever & Vanbeveren . 69 2.4.2 Analytic calculation by Wu (2001) . 72 2.4.3 Semi-analytical calculation by Ghosh & White (2001) 73 2.4.4 Comparison with observations . 74 2.4.5 Further applications of the simulation results . 76 3 A snapshot survey of nearby mildly-active galaxies with Chandra 84 3.1 Introduction . 84 3.2 Data analysis . 85 3.3 Results . 94 3.3.1 Target descriptions and notable trends . 97 3.4 Epilogue . 105 4 Nova Sco and coalescing low mass black hole binaries as LIGO sources 149 4.1 Introduction . 150 4.2 Example of Nova Sco . 155 4.3 Population synthesis . 158 4.4 Results . 160 4.5 Discussion . 165 Bibliography 176 vi List of Figures 2.1 Evolution of total X-ray luminosity . 56 2.2 Evolution of BH/XRB population, Salpeter IMF, low q . 57 2.3 Evolution of NS/XRB population, Salpeter IMF, low q . 58 2.4 Evolution of BH/XRB population, Miller-Scalo IMF, low q . 59 2.5 Evolution of NS/XRB population, Miller-Scalo IMF, low q . 60 2.6 Evolution of BH/XRB population, Salpeter IMF, flat q . 61 2.7 Evolution of NS/XRB population, Salpeter IMF, flat q . 62 2.8 Evolution of BH/XRB population, Miller-Scalo IMF, flat q . 63 2.9 Evolution of NS/XRB population, Miller-Scalo IMF, flat q . 64 2.10 Luminosity function at five epochs, Salpeter IMF, low q . 65 2.11 Luminosity function at five epochs, Miller-Scalo IMF, low q . 66 2.12 Luminosity function at five epochs, Salpeter IMF, flat q . 67 2.13 Luminosity function at five epochs, Miller-Scalo IMF, flat q . 68 2.14 Hα luminosity evolution for the first 2 Gyr after star formation 80 2.15 X-ray luminosity versus Hα compared to Ho et al. 83 3.1 L vs. B and (B V ) . 106 X T − T 3.2 LX frequency by host galaxy type . 107 vii 3.3 Colour-magnitude diagram and luminosity function for NGC 253, 404, 660 and 1052 . 127 3.4 Colour-magnitude diagram and luminosity function for NGC 1055, 1058, 2541 and 2683 . 128 3.5 Colour-magnitude diagram and luminosity function for NGC 2787, 2841, 3031 and 3368 . 129 3.6 Colour-magnitude diagram and luminosity function for NGC 3486, 3489, 3623 and 3627 . 130 3.7 Colour-magnitude diagram and luminosity function for NGC 3628, 3675, 4150 and 4203 . 131 3.8 Colour-magnitude diagram and luminosity function for NGC 4278, 4314, 4321 and 4374 . 132 3.9 Colour-magnitude diagram and luminosity function for NGC 4395, 4414, 4494 and 4565 . 133 3.10 Colour-magnitude diagram and luminosity function for NGC 4569, 4579, 4594 and 4639 . 134 3.11 Colour-magnitude diagram and luminosity function for NGC 4725, 4736, 4826 and 5033 . 135 3.12 Colour-magnitude diagram and luminosity function for NGC 5055, 5195, 5273 and 6500 . 136 3.13 Colour-magnitude diagram and luminosity function for NGC 6503137 3.14 NGC 253, 404, 660 and 1052 . 138 3.15 NGC 1055, 1058, 2541 and 2683 . 139 3.16 NGC 2787, 2841, 3031 and 3368 . 140 3.17 NGC 3486, 3489, 3623 and 3627 . 141 3.18 NGC 3628, 3675, 4150 and 4203 . 142 3.19 NGC 4278, 4314, 4321 and 4374 . 143 viii 3.20 NGC 4395, 4414, 4494 and 4565 . 144 3.21 NGC 4569, 4579, 4594 and 4639 . 145 3.22 NGC 4725, 4736, 4826 and 5033 . 146 3.23 NGC 5055, 5195, 5273 and 6500 . 147 3.24 NGC 6503 . 148 4.1 a vs. e for BH-BH and BH-NS systems . 171 4.2 Two mass distribution histograms for bound BH-BH systems 172 4.3 Chirp mass distribution for merging systems . 173 4.4 Merger time vs. final binary velocity . 174 ix List of Tables 2.1 Simulation parameters summary . 46 2.2 Power-law index of model cummulative luminosity function at five epochs . 77 3.1 Observed sample of nearby LLAGN galaxies . 92 3.1 Observed sample of nearby LLAGN galaxies . 93 3.2 Summary of source properties . 108 3.2 Summary of source properties . 109 3.2 Summary of source properties . 110 3.2 Summary of source properties . 111 3.2 Summary of source properties . 112 3.2 Summary of source properties . 113 3.2 Summary of source properties . 114 3.2 Summary of source properties . 115 3.2 Summary of source properties . 116 3.2 Summary of source properties . 117 3.2 Summary of source properties . 118 3.2 Summary of source properties . 119 3.2 Summary of source properties . 120 x 3.2 Summary of source properties . 121 3.2 Summary of source properties . 122 3.2 Summary of source properties . 123 3.2 Summary of source properties . 124 3.2 Summary of source properties . 125 3.2 Summary of source properties . 126 4.1 Summary of source properties . 169 4.2 Summary of source properties . 170 xi Acknowledgements It is my great pleasure to thank the members of my thesis committee for their insightful comments and accumulated scientific wisdom. Thanks go most especially to my advisor(s), Herr Doktor Professors Mike Eracleous and Steinn Sigurdsson. Without their encouragement and (ahem) stern discipline, I should likely still be writing this thesis, and only half as well at that. Comraderie is the bulwark of any graduate student's morale, and I have been indeed fortunate to have had some exceptional peers during my tenure at Penn State.
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