Optical spectra of thermonuclear supernovae in the local and distant universe [Elektronische Ressource] / vorgelegt von Stéphane Blondin

Stephane Blondin

Sujets

• Astronomie

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2005
• Nombre de lectures: 6
• Langue: English
• Poids de l'ouvrage: 19 Mo

Extrait

Optical Spectra of Thermonuclear
Supernovae in the Local and Distant
Universe
Stephane Blondin
Mun chen 2005Optical Spectra of Thermonuclear
Supernovae in the Local and Distant
Universe
Stephane Blondin
Dissertation
an der Fakulatt fur Physik
der Ludwig–Maximilians–Universiatt
Munc hen
vorgelegt von
Stephane Blondin
aus Paris
Munc hen, den 11.08.2005Erstgutachter: Prof. Adalbert Pauldrach
Zweitgutachter: Priv. Doz. Achim Weiss
Tag der mundlic hen Prufung: 07.11.2005For my Peruvian queen
and our Franco-Peruvian princessviContents
Summary xvii
Zusammenfassung xix
1 Introduction 1
1.1 General properties of thermonuclear supernovae . . . . . . . . . . . . . . . 1
1.1.1 The confusing and misleading classi cation of supernovae . . . . . . 1
1.1.2 Progenitors of Type Ia supernovae . . . . . . . . . . . . . . . . . . 6
1.1.3 Light curves and explosion models of Type Ia supernovae . . . . . . 7
1.2 Type Ia supernovae as distance indicators . . . . . . . . . . . . . . . . . . 11
1.3 Cosmology with Type Ia supernovae . . . . . . . . . . . . . . . . . . . . . 13
1.3.1 Friedmann-Robertson-Walker cosmology . . . . . . . . . . . . . . . 13
1.3.2 Luminosity distances and the accelerating universe . . . . . . . . . 17
1.3.3 Measuring the equation-of-state parameter of “Dark Energy” . . . . 23
1.4 Testing for evolution in the SN Ia sample at di erent redshifts . . . . . . . 25
2 Optical spectra of Type Ia supernovae 31
2.1 Modeling Type Ia supernova spectra . . . . . . . . . . . . . . . . . . . . . 31
2.1.1 Velocity eld and density/abundance structure in SN Ia ejecta . . . 31
2.1.2 Sources of opacity in SN Ia ejecta . . . . . . . . . . . . . . . . . . . 33
2.1.3 Line formation and line pro les in SN Ia spectra . . . . . . . . . . . 39
2.1.4 A parametrized synthetic SN Ia spectrum . . . . . . . . . . . . . . 44
2.2 Observational properties of Type Ia supernovae . . . . . . . . . . . . . . . 47
2.2.1 Spectral evolution of SN Ia . . . . . . . . . . . . . . . . . . . . . . . 47
2.2.2 Homogeneity vs. inhomogeneity in SN Ia spectra . . . . . . . . . . 50
2.3 Observations of Type Ia supernovae and data reduction . . . . . . . . . . . 52
2.3.1 Discovery of a supernova and spectroscopic follow-up . . . . . . . . 52
2.3.2 Standard approach to reducing supernova spectra . . . . . . . . . . 56
2.3.3 A novel method to extract SN spectra . . . . . . . . . . . . . . . . 59
3 Extracting clean supernova spectra 69
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.2 The algorithm and its implementation . . . . . . . . . . . . . . . . . . . . 71viii CONTENTS
3.2.1 Decomposing the SN from its host galaxy . . . . . . . . . . . . . . 71
3.2.2 Practical implementation for SN and host galaxy . . . . . . . . . . 72
3.3 The importance of the slit spread function . . . . . . . . . . . . . . . . . . 73
3.3.1 Measuring the seeing . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.3.2 Generating synthetic PSF spectra . . . . . . . . . . . . . . . . . . . 74
3.3.3 Impact of the SSF on spectral restoration . . . . . . . . . . . . . . 77
3.4 The spatial resolution kernel . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.5 Testing the algorithm on simulated data . . . . . . . . . . . . . . . . . . . 83
3.5.1 Simulated data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.5.2 Simulation steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.5.3 Simulation results and discussion . . . . . . . . . . . . . . . . . . . 92
3.6 Testing the algorithm on real data . . . . . . . . . . . . . . . . . . . . . . 92
3.7 Comparison with other methods . . . . . . . . . . . . . . . . . . . . . . . 94
3.7.1 Standard extraction in IRAF . . . . . . . . . . . . . . . . . . . . . 97
3.7.2 Gaussextract – an iterative Gaussian extractor . . . . . . . . . . . . 98
3.7.3 Statistical approach usingSN- t . . . . . . . . . . . . . . . . . . . 98
3.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4 A tool to determine supernova redshifts 101
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.2 Cross-correlation techniques . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.2.1 Pre-processing the supernova spectrum . . . . . . . . . . . . . . . . 104
4.2.2 Estimation of redshift . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.2.3 Estimation of error . . . . . . . . . . . . . . . . . . . . . . 114
4.3 Variation of the redshift error with redshift, phase, and spectral range . . . 117
4.4 Accuracyofthecross-correlationmethod: comparisonofSNandhostgalaxy
redshifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
4.5 Future developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
5 Using line pro les to test the fraternity of Type Ia supernovae at high
and low redshifts 133
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.2 Measurement techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
5.2.1 Smoothing Supernova Spectra . . . . . . . . . . . . . . . . . . . . . 136
5.2.2 Error Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
5.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
5.3.1 Absorption Velocities . . . . . . . . . . . . . . . . . . . . . . . . . . 148
5.3.2 Emission-Peak Velocities . . . . . . . . . . . . . . . . . . . . . . . . 157
5.3.3 Double-Absorption Features in Caii 3945 . . . . . . . . . . . . . . 162
5.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166CONTENTS ix
6 Time-dilation e ects in high-redshift Type Ia supernova spectra 183
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
6.2 Determining the phase of a SN Ia via cross-correlation . . . . . . . . . . . 185
6.3 Testing for time dilation in high-z SN Ia spectra . . . . . . . . . . . . . . . 189
6.3.1 Spectral phases in high-z SN Ia . . . . . . . . . . . . . . . . . . . . 189
6.3.2 Determining the age factor . . . . . . . . . . . . . . . . . . . . . . . 191
6.3.3 Time dilation from multi-epoch spectra of SN 2002iy at z = 0.587 . 192
6.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
7 Conclusion 199
A Spectroscopy of high-redshift supernovae from the ESSENCE project:
the rst 2 years 203
A.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
A.2 Target Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
A.3 Observations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
A.4 Target Identi cation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
A.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
A.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
Bibliography 264
Acknowledgements 265
Curriculum Vitae 267x CONTENTS