Cosmological Distances of Type II Supernovae from Radiative Transfer Modeling
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Cosmological distances of type II supernovae from radiative transfer modeling Dissertation Christian Vogl TECHNISCHE UNIVERSITAT¨ MUNCHEN¨ MAX-PLANCK-INSTITUT FUR¨ ASTROPHYSIK Cosmological distances of type II supernovae from radiative transfer modeling Christian Vogl Vollst¨andigerAbdruck der von der Fakult¨atf¨urPhysik der Technischen Universit¨atM¨unchen zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) genehmigten Dissertation. Vorsitzende(r): Prof. Dr. Stefan Sch¨onert Pr¨uferder Dissertation: 1. Hon.-Prof. Dr. Wolfgang Hillebrandt 2. Prof. Dr. Bruno Leibundgut Die Dissertation wurde am 07.04.2020 bei der Technischen Universit¨atM¨unchen eingereicht und durch die Fakult¨atf¨urPhysik am 24.06.2020 angenommen. Abstract There is a great need for independent accurate determinations of the Hubble constant (H0). We establish a new one-step method to measure H0 based on radiative transfer modeling of type II supernovae. Our approach relies on luminosity estimates from the tailored-expanding-photosphere method. As a starting point, we create a new type II supernova radiative transfer code through substantial extensions of the Monte Carlo spectral synthesis code Tardis. This allows us to calculate large grids of radiative transfer models fast but accurately. The model grids serve as training data for a machine learning emulator, which reproduces the output of our simulations with high precision 7 (. 1 %) but ∼ 10 times faster. This tremendous speedup makes it possible, for the first time, to fit type II supernova spectra in a reproducible manner through numerical optimization. We demonstrate the utility of the developed tools in a proof-of-principle H0 measurement. In this first-ever application of the tailored-expanding-photosphere +2.9 −1 −1 method in the Hubble flow, we find H0=72.3−2.8 km s Mpc in good agreement with state-of-the-art measurements. Currently, the small set of available observational data limits the accuracy. Our dedicated observing program will significantly improve this situation and pave the way towards a highly competitive H0 determination in the near future. Zusammenfassung Der Bedarf an unabh¨angigen, genauen Bestimmungen der Hubble-Konstante (H0) ist groß. Wir etablieren hier eine neue direkte Methode zur Messung von H0 basierend auf Modellrechnungen zum Strahlungstransport in Typ-II-Supernovae. Unser Ansatz be- ruht auf einer Bestimmung der Supernova-Helligkeiten mithilfe von maßgeschneiderten ” EPM“. Hierzu entwickeln wir einen neuen Typ-II-Supernova-Strahlungstransportcode durch umfassende Erweiterungen des existierenden Monte-Carlo-Codes Tardis. Dies erm¨oglicht es uns, große Gitter von Strahlungstransportmodellen schnell und genau zu berechnen. Die Modellgitter dienen als Trainingsdaten fur¨ einen Emulator der auf Basis maschinellen Lernens die Ergebnisse unserer Simulationen mit hoher Pr¨azision 7 (. 1 %), aber ∼ 10 mal schneller reproduziert. Diese enorme Zeitersparnis macht es erstmals m¨oglich, Strahlungstransportmodelle von Typ-II-Supernovae fur¨ individuelle beobachtete Spektren numerisch zu optimieren. Anhand einer H0-Messung demons- trieren wir, dass die neu entwickelte Methode funktioniert. Diese erste Anwendung der maßgeschneiderten EPM“ auf Supernovae im Hubble-Fluss ergibt ein H0 von ” +2.9 −1 −1 ¨ 72.3−2.8 km s Mpc , in guter Ubereinstimmung mit anderen modernen Messungen. Derzeit begrenzt die geringe Menge an verfugbaren¨ Beobachtungsdaten die Genauigkeit. Unser dediziertes Beobachtungsprogramm wird diese Situation maßgeblich verbessern und eine konkurrenzf¨ahige Messung von H0 erm¨oglichen. Contents I Introduction and methodology1 1 The expanding Universe 2 1.1 History ......................................... 3 1.2 Basics of cosmography................................. 7 1.2.1 Cosmological redshift ............................. 8 1.2.2 Cosmological time dilation .......................... 13 1.2.3 Hubble-Lemaˆıtrelaw.............................. 13 1.2.4 Hubble constant and related parameters................... 14 1.2.5 Distance measures............................... 14 2 The cosmic distance scale and the Hubble tension 17 2.1 Distance ladder..................................... 18 2.2 Maser galaxies ..................................... 26 2.3 Time-delay cosmography................................ 29 3 Type II supernovae: the Hubble constant in one step 33 3.1 Type II supernova basics................................ 33 3.1.1 Progenitors................................... 34 3.1.2 Explosion mechanism ............................. 35 3.1.3 Light curves................................... 36 3.1.4 Spectra ..................................... 39 3.1.5 Polarimetry................................... 44 3.2 Expanding photosphere method............................ 44 3.2.1 Basic principle ................................. 45 3.2.2 Challenges ................................... 47 II A new type II supernova radiative-transfer code 53 4 Introduction 56 5 Method 58 v Contents 5.1 Monte Carlo simulations................................ 58 5.1.1 Packet propagation............................... 59 5.1.2 Macro atom................................... 60 5.1.3 Reconstruction of radiation field quantities ................. 60 5.1.4 Relativistic transfer .............................. 61 5.2 Plasma state ...................................... 62 5.2.1 Excitation.................................... 62 5.2.2 Ionization.................................... 63 5.2.3 Thermal balance................................ 64 5.2.4 Outer plasma iteration............................. 65 5.3 Approximations..................................... 66 5.4 Iteration cycle...................................... 66 5.5 Atomic data....................................... 67 5.6 Spectral synthesis.................................... 68 5.7 Supernova model.................................... 68 6 Expanding photosphere method 70 6.1 Presentation of the method .............................. 70 6.2 Dilution factors..................................... 72 7 Example spectra 73 8 Model grid 75 9 Results 77 9.1 Overview ........................................ 77 9.2 Influence of atmospheric properties.......................... 80 10 Comparison to previous studies 84 10.1 Radiative transfer ................................... 84 10.2 Effect of model grid assumptions........................... 86 11 Conclusions 89 III Automated spectroscopic analysis 91 12 Introduction 94 13 Parametrized supernova models with TARDIS 96 14 Creation of a SN II spectral training set 97 vi Contents 15 Spectral emulator 100 15.1 Preprocessing and dimensionality reduction..................... 100 15.2 Gaussian process interpolation ............................ 102 15.2.1 Spectra ..................................... 102 15.2.2 Absolute magnitudes.............................. 103 16 Evaluation of the emulator performance 105 16.1 Spectra ......................................... 105 16.2 Absolute magnitudes.................................. 106 17 Learning behavior of the emulator 110 18 Modeling observations 112 18.1 Likelihood for parameter inference .......................... 112 18.2 Fitting observed spectra................................ 113 18.2.1 SN 1999em ................................... 113 18.2.2 SN 2005cs.................................... 115 18.3 Distance measurements ................................ 117 18.3.1 SN 1999em ................................... 120 18.3.2 SN 2005cs.................................... 120 19 Conclusions and outlook 123 IV H0 from the tailored-expanding-photosphere method 125 20 Past and ongoing observational programs 126 20.1 Nearby Supernova Factory............................... 126 20.2 ESO VLT large programme.............................. 128 21 Proof-of-principle measurement 133 21.1 Observational data................................... 133 21.2 Time of explosion.................................... 134 21.3 Distance determinations................................ 140 21.4 Hubble constant .................................... 141 22 Conclusions 152 vii List of Figures 1.1 Multi-wavelength view of the expanding Universe ................. 3 1.2 First Hubble diagram................................. 6 1.3 History of H0 measurements ............................. 7 1.4 Illustration of cosmic expansion ........................... 9 1.5 Cosmological redshift of galaxy lines......................... 10 1.6 Impact of peculiar velocities on the observed redshift ............... 12 2.1 Hubble tension development ............................. 19 2.2 Cosmic distance ladder ................................ 20 2.3 Cepheid period-luminosity relations......................... 23 2.4 Type Ia supernovae as standardizable candles.................... 24 2.5 Water megamaser in NGC 4258............................ 27 2.6 Lensed quasar light curves and time delays..................... 30 3.1 Life, death, and disappearance of a red supergiant................. 35 3.2 Photosphere of type II supernovae on the plateau ................. 37 3.3 V -band light curves of normal type II supernovae ................. 38 3.4 Spectroscopic evolution of type II supernovae.................... 40 3.5 P-cygni line formation................................. 41 3.6 Evolution of the photospheric composition in type II supernovae......... 42 3.7 Determination of distance and time of explosion in the expanding-photosphere method......................................... 46 3.8 Difference between line absorption and photospheric