Radiative transfer in hot gas of galaxy clusters: constraints on ICM turbulence [Elektronische Ressource] / Irina Zhuravleva. Betreuer: Rashid Sunyaev

Irina Zhuravleva

Sujets

• Astronomie

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2011
• Nombre de lectures: 15
• Langue: English
• Poids de l'ouvrage: 6 Mo

Extrait

Radiative transfer in hot gas of galaxy
clusters: constraints on ICM turbulence
Irina Zhuravleva
Mu¨nchen 2011Radiative transfer in hot gas of galaxy
clusters: constraints on ICM turbulence
Irina Zhuravleva
Dissertation
an der Fakult¨at fu¨r Physik
der Ludwig–Maximilians–Universit¨at
Mu¨nchen
vorgelegt von
Irina Zhuravleva
aus Pestovo, Russland
Mu¨nchen, den 26. September 2011Erstgutachter: Prof. Dr. Rashid Sunyaev
Zweitgutachter: Prof. Dr. Hans B¨ohringer
Tag der mundl¨ ichen Pruf¨ ung: 4. November 2011Contents
Zusammenfassung xiii
Summary xv
1 Introduction 1
1.1 Galaxy clusters as cosmological and astrophysical laboratories . . . . . . . 1
1.2 Hot X-ray gas: spectrum and radiation mechanisms . . . . . . . . . . . . . 3
1.3 Gas motions in the ICM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Basics of resonant scattering . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.1 Optical depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.2 Phase function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Resonant scattering: surface brightness and line shape . . . . . . . . . . . 12
1.5.1 Impact on surface brightness profile and abundance . . . . . . . . . 12
1.5.2 Impact on the line shape . . . . . . . . . . . . . . . . . . . . . . . . 14
1.6 Resonant scattering: sensitivity to the velocity field of hot gas . . . . . . . 14
1.7 Structure of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 Constraints on turbulence in the X-ray halos of giant elliptical galaxies 21
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2 Sample and XMM-Newton observations . . . . . . . . . . . . . . . . . . . . 24
2.3 Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3.1 XMM-Newton RGS data analysis . . . . . . . . . . . . . . . . . . . 25
2.3.2 Chandra analysis of NGC 4636 . . . . . . . . . . . . . . . . . . . . 29
2.4 Observations of resonant scattering . . . . . . . . . . . . . . . . . . . . . . 30
2.5 Modelling of resonant scattering in NGC 4636 . . . . . . . . . . . . . . . . 32
2.6 Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3 Resonant scattering in galaxy clusters for anisotropic gas motions 47
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.2 Line profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.2.1 The influence of microturbulent gas motions on the line profiles . . 49
3.2.2 The Influence of Large-Scale Gas Motions on the Line Profiles . . . 53
3.3 The Influence of the Velocity Field on Resonant Scattering . . . . . . . . . 56vi CONTENTS
3.4 Cluster Model and Scattering Calculation . . . . . . . . . . . . . . . . . . 57
3.4.1 Gas Temperature and Density Distributions . . . . . . . . . . . . . 57
3.4.2 Velocity Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.4.3 Monte Carlo Simulations of Scattering . . . . . . . . . . . . . . . . 61
3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.7 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4 Polarization of X-ray lines from galaxy clusters 71
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.2 Resonant scattering and promising lines . . . . . . . . . . . . . . . . . . . 77
4.3 Monte-Carlo simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.3.1 Spherically symmetric clusters . . . . . . . . . . . . . . . . . . . . . 80
4.3.2 Full 3D clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.4 Spherically symmetric problems . . . . . . . . . . . . . . . . . . . . . . . . 81
4.4.1 Perseus cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.4.2 M87/Virgo cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.4.3 Degree of polarization without bulk motions . . . . . . . . . . . . . 83
4.4.4 Canonical cooling flow model . . . . . . . . . . . . . . . . . . . . . 87
4.4.5 Spherical shock model . . . . . . . . . . . . . . . . . . . . . . . . . 89
4.5 Three-dimensional problem. . . . . . . . . . . . . . . . . . . . . . . . . . . 91
4.5.1 Major merger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
4.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.7 Requirements for future X-ray polarimeters. . . . . . . . . . . . . . . . . . 107
4.8 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5 Constraints on the ICM velocity power spectrum from the X-ray lines 119
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.2 Basic assumptions and models . . . . . . . . . . . . . . . . . . . . . . . . . 124
5.3 Observables and 3D velocity power spectrum . . . . . . . . . . . . . . . . . 125
5.4 Structure function and velocity dispersion . . . . . . . . . . . . . . . . . . 127
5.5 Length scales of motions and observed RMS velocity . . . . . . . . . . . . 131
5.6 Recovering 3D velocity power spectrum from 2D projected velocity . . . . 132
5.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
5.7.1 Limiting cases of small and large scale motions. . . . . . . . . . . . 135
5.7.2 Effect of thermal broadening and metallicity . . . . . . . . . . . . . 135
5.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
5.9 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
5.10 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
5.10.1 3D velocity power spectrum and projected velocity field . . . . . . . 139
5.10.2 3D velocity power spectrum and projected velocity dispersion . . . 140
5.10.3 Relation between structure function and cored power law 3D PS . . 140
5.10.4 Relation between velocity dispersion along the line of sight and PS 141Inhaltsverzeichnis vii
5.10.5 Ratio of observed RMS velocity to observed velocity dispersion . . . 142
6 A method to calculate power spectrum from data with gaps 147
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
6.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
6.2.1 Data without gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
6.2.2 Data with gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
6.3 Test on simulated images . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
6.4 3D data cubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
6.6 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.6.1 Cartesian coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.6.2 Normalization bias for a power law spectrum . . . . . . . . . . . . . 163
7 Conclusions 167
Acknowledgements 171viii InhaltsverzeichnisList of Figures
1.1 Coma cluster in X-ray, optical, radio and Sunyaev-Zeldovich observations . 2
1.2 Theoretical model of typical X-ray spectrum from galaxy clusters . . . . . 4
1.3 Perseus spectrum with Chandra and Astro-H observatory . . . . . . . . . . 6
1.4 Model of the Kolmogorov-like power spectrum of turbulence . . . . . . . . 7
1.5 Velocity power spectra in SPH and AMR simulations . . . . . . . . . . . . 7
1.6 Velocity field in simulated galaxy cluster . . . . . . . . . . . . . . . . . . . 8
1.7 Optical depth and radial intensity profile of 6.7 keV FeXXV line in Perseus 13
1.8 Spectral profile of the 6.7 keV line in the center and outskirts of Perseus . 15
1.9 Resonant scattering in Perseus cluster. . . . . . . . . . . . . . . . . . . . . 16
2.1 Fraction of Fexvii as a function of temperature . . . . . . . . . . . . . . . 23
2.2 Chandra image of NGC 4636 with the RGS extraction regions over-plotted 25
2.3 Chandra images of the giant elliptical galaxies in our sample . . . . . . . . 26
2.4 RGS spectra for NGC 5813, NGC 1404, NGC 4649, and NGC 4472 . . . . 28
2.5 XMM-Newton RGS spectra from the core of NGC 4636 . . . . . . . . . . . 31
2.6 Observed radial profiles of n and T in NGC 4636 . . . . . . . . . . . . . . 34e
˚2.7 Optical depth of the 15.01 A line in NGC4636 . . . . . . . . . . . . . . . . 36
˚2.8 Resonant scattering of the 15.01 A line in NGC4636 . . . . . . . . . . . . . 37
2.9 The deprojected temperature profile of NGC 4649 . . . . . . . . . . . . . . 39
3.1 Spectral profiles of the 6.7 keV line for inisotropic turbulence . . . . . . . . 52
3.2 Profiles of the 6.7 keV line for nine lines-of-sight . . . . . . . . . . . . . . . 54
3.3 Averaged profiles of the 6.7 keV line . . . . . . . . . . . . . . . . . . . . . 55
3.4 Spectral profiles of 6.7 keV line calculated in cluster center and outskirts . 55
3.5 RMS amplitudes of radial and tangential gas motions . . . . . . . . . . . . 59
3.6 Power spectrum of gas motions in simulated cluster . . . . . . . . . . . . . 60
3.7 Resonant scattering at 6.7 keV line for various models of gas motions . . . 6