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Properties of the integrated spectrum of active galactic nuclei [Elektronische Ressource] / Pooja Chaudhary. Betreuer: Ralf Bender

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Properties of the integrated spectrum ofactive galactic nucleiPooja ChaudharyMu¨nchen 2011Properties of the integrated spectrum ofactive galactic nucleiPooja ChaudharyDissertationan der Fakulta¨t fu¨r Physikder Ludwig–Maximilians–Universita¨t¨Munchenzur Erlangung des GradesDoktor der NaturwissenschaftenDr.rer.nat.vorgelegt vonPooja Chaudharyaus Uttar Pradesh, IndiaMu¨nchen, Oktober 2011Erstgutachter: Prof. Dr. Ralf BenderZweitgutachter: Prof. Kirpal NandraTag der mu¨ndlichen Pru¨fung: den 24. November 2011Contents1 Introduction 11.1 A brief history of AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Observational characteristics of AGNs . . . . . . . . . . . . . . . . . . . . . . . 31.2.1 Broad band continuum . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2.2 Broad and high ionization emission lines . . . . . . . . . . . . . . . . . 41.2.3 Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.2.4 Jets and outflows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3 X-ray emission from AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.4 The unified model for AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.5 Accretion onto a black hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.5.1 Basic parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.5.2 The Eddington limit . . . . . . . . . . . . . . . . . . .

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Properties of the integrated spectrum of
active galactic nuclei
Pooja Chaudhary
Mu¨nchen 2011Properties of the integrated spectrum of
active galactic nuclei
Pooja Chaudhary
Dissertation
an der Fakulta¨t fu¨r Physik
der Ludwig–Maximilians–Universita¨t
¨Munchen
zur Erlangung des Grades
Doktor der Naturwissenschaften
Dr.rer.nat.
vorgelegt von
Pooja Chaudhary
aus Uttar Pradesh, India
Mu¨nchen, Oktober 2011Erstgutachter: Prof. Dr. Ralf Bender
Zweitgutachter: Prof. Kirpal Nandra
Tag der mu¨ndlichen Pru¨fung: den 24. November 2011Contents
1 Introduction 1
1.1 A brief history of AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Observational characteristics of AGNs . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 Broad band continuum . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.2 Broad and high ionization emission lines . . . . . . . . . . . . . . . . . 4
1.2.3 Variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.4 Jets and outflows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 X-ray emission from AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4 The unified model for AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Accretion onto a black hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.5.1 Basic parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.5.2 The Eddington limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.5.3 Accretion disks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.5.4 Accretion disk coronae . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.6 Iron Kα line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1.6.1 The iron line profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.6.2 Dependence of the line profile on disk inclination and emissivity . . . . . 25
1.6.3 Dependence of the line profile on the inner disk radius and black hole spin 26
1.7 Observations of iron lines in AGNs . . . . . . . . . . . . . . . . . . . . . . . . . 27
1.8 This thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
1.9 Outline of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2 Sample preparation 31
2.1 XMM-Newton observatory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2 The 2XMM catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.3 Quality evaluation of the archival products . . . . . . . . . . . . . . . . . . . . . 36
2.4 The sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3 Properties of the integrated spectrum of serendipitous 2XMM catalog sources 41
3.1 Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2 Splitting the sample in redshift and luminosity bins . . . . . . . . . . . . . . . . 42
3.3 Computation and spectral fitting of the integrated spectrum . . . . . . . . . . . . 43
3.3.1 Contribution from single sources . . . . . . . . . . . . . . . . . . . . . . 44vi Content
3.4 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.5 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.5.1 Evolution of the Fe line equivalent width with redshift . . . . . . . . . . 56
3.5.2 The IT effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4 Rest-frame stacking of 2XMM catalog sources: Properties of the Fe Kα line 63
4.1 Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2 The sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3 Rest-frame stacking procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.3.1 Stacked ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.3.2 Stacked spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.3.3 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.4.1 “Averaged ratio flux spectrum” fitting . . . . . . . . . . . . . . . . . . . 70
4.4.2 “Averaged X-ray spectrum” fitting . . . . . . . . . . . . . . . . . . . . . 73
4.4.3 Complex fits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5 Summary and future perspectives 87
5.1 Future perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Appendix 91
A.1 Background normalization inXSPEC . . . . . . . . . . . . . . . . . . . . . . . . 91
A.2 Observed-frame stacking procedure . . . . . . . . . . . . . . . . . . . . . . . . 92
A.3 The sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Bibliography 103
Acknowledgments 114List of Figures
1.1 Schematic representation of the broadband continuum spectral energy distribu-
tion (SED) observed in the different types of AGNs . . . . . . . . . . . . . . . . 4
1.2 Optical spectra of many different types of AGNs as compared to a normal galaxy 5
1.3 Examples of line and continuum flux variability seen at different wavelengths in
various types of AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 Hubble Space Telescope (HST) high-resolution spectrum of the C IV λ1550 re-
gion in the Seyfert 1 galaxy NGC 5548 . . . . . . . . . . . . . . . . . . . . . . . 7
1.5 Monte Carlo simulations of the X-ray reflection spectrum from a slab of uniform
density neutral matter with solar abundances . . . . . . . . . . . . . . . . . . . . 10
1.6 A schematic representation of the intrinsic type-1 (unabsorbed) AGN X-ray spec-
trum in the 0.1–400 keV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.7 Schematic picture illustrating the main components of an AGN as postulated by
the unified model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.8 A series of schematic, logarithmic views of the basic AGN components embed-
ded in the host galaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.9 Possible geometries for an accretion disk corona . . . . . . . . . . . . . . . . . . 21
1.10 Ionized reflection spectra for different ionization parameters . . . . . . . . . . . 23
1.11 Schematic illustration of the iron line shape distortion caused by the interplay
of Doppler and transverse Doppler shifts, relativistic beaming, and gravitational
redshifting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
1.12 The dependence of the line profile on the observer inclination and disk emissivity
profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.13 The dependence of the line profile on the inner disk radius . . . . . . . . . . . . 26
2.1 On-axis effective area of the EPIC-PN and EPIC-MOS1 cameras on-board XMM-
Newton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2 A simplified schematic of the data processing steps undertaken in the creation of
the 2XMM catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3 Comparison of the EPIC-PN spectra extracted from the raw observation data files
with the pipeline processed archival spectra for four sources . . . . . . . . . . . 37
2.4 An example 2XMM EPIC-PN 0.2–12 keV image in which the background an-
nulus is contaminated by three sources . . . . . . . . . . . . . . . . . . . . . . . 38viii LIST OF FIGURES
2.5 Comparison of the distributions of the EPIC-PN net counts and flux in the observed-
frame 0.2–12 keV band for the total sample of 2646 point sources selected from
the 2XMM catalog, its sub-sample of 919 objects with redshift available and our
final sample of 507 sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.1 Spectral fits to the stacked spectra in different redshift and luminosity bins (1) . . 46
3.2 Spectral fits to the stacked spectra in different redshift and luminosity bins (2) . . 47
3.3 Comparison of the simulated and real stacked spectra (1) . . . . . . . . . . . . . 49
3.4 Comparison of the simulated and real stacked spectra (2) . . . . . . . . . . . . . 50
3.5 Histograms of the simulated stacked spectrum fit parameters in the redshift bins
(1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.6 Histograms of the simulated stacked spectrum fit parameters in the redshift bins
(2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.7 Comparison of the power law photon indices of the real and simulated stacked
spectra in the quoted redshift and luminosity bins . . . . . . . . . . . . . . . . . 53
3.8 Comparison of the 2–10 keV X-ray luminosities of the real and simulated stacked
spectra in the quoted redshift and luminosity bins . . . . . . . . . . . . . . . . . 54
3.9 Comparison of the narrow Fe Kα lines equivalent widths in the real and simulated
stacked spectra in the quoted redshift and luminosity bins . . . . . . . . . . . . . 55
3.10 Rest-frame equivalent width as a function of redshift. . . . . . . . . . . . . . . . 56
3.11 Variation of the narrow Fe Kα line equivalent width with the X-ray luminosity
in the redshift range 0 < z < 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.12 Variation of the narrow Fe Kα line equivalent width with the X-ray luminosity
in the redshift range 0 < z < 0.8 . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.13 X-ray luminosity dependence of the power law photon index . . . . . . . . . . . 60
4.1 Comparison of the distributions of the net counts, power law photon indices,
redshifts and X-ray luminosities for the reference (final) sample of 507 sources
and the sample of 248 sources selected for the rest-frame stacking analysis . . . . 65
4.2 Six redshift corrected source spectra grouped in 26 predefined energy bins in the
2–10 keV band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.3 Comparison of the mean ratio profiles . . . . . . . . . . . . . . . . . . . . . . . 68
4.4 Ratio of the “averaged X-ray spectrum” with respect to a power law overlaid
with the mean ratio profile of the 248 sources created using 3–sigma clipping . . 69
4.5 Averaged ratio of the 248 spectra after applying 3–sigma clipping, mean simu-
lated continuum along with its 1σ and 3σ confidence limits . . . . . . . . . . . . 70
4.6 Spectral fits to the “averaged ratio flux spectrum” . . . . . . . . . . . . . . . . . 72
4.7 Contour plots of thediskline versus narrow component intensities for the “av-
eraged ratio flux spectrum” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.8 Contour plots of thediskline versus narrow component intensities for the “av-
eraged X-ray spectrum” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.9 Spectral fits to the “averaged X-ray spectrum” . . . . . . . . . . . . . . . . . . . 75List of figures ix
4.10 Spectral fit to the “averaged ratio flux spectrum” using a model including a power
law, a distant neutral reflector and a diskline . . . . . . . . . . . . . . . . . . . . 77
4.11 Spectral fit to the “averaged ratio flux spectrum” using a power law and dual
neutral reflection spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.12 Spectral fits to the “averaged X-ray spectrum” using complex models . . . . . . . 80
4.13 Equivalent width of the narrow Fe Kα line measured from the spectral fitting of
the “averaged ratio flux spectrum” and “averaged X-ray spectrum” of the total
sample comprising 248 AGNs and the sub-samples used in three hard X-ray
luminosity bins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.14 Comparison of the equivalent width of the broad Fe Kα line measured from
the spectral fitting of the “averaged ratio flux spectrum” and “averaged X-ray
spectrum” of the total sample comprising 248 AGNs . . . . . . . . . . . . . . . 83