Optical alignment and characterization of FIFI-LS - the far-infrared field imaging line spectrometer for SOFIA and Spitzer IRS observations of active galaxies [Elektronische Ressource] / vorgelegt von Mario Schweitzer

Mario Schweitzer

Sujets

• Astronomie

Informations

• Publié par: ludwig-maximilians-universitat_munchen
• Publié le: 01 janvier 2008
• Nombre de lectures: 14
• Langue: English
• Poids de l'ouvrage: 7 Mo

Extrait

Optical Alignment and Characterization
of FIFI-LS -the Far-Infrared Field
Imaging Line Spectrometer forSOFIA
and
Spitzer IRS Observations of Active
Galaxies
DISSERTATION
der Fakult¨at fu¨r Physik der Ludwig-Maximilians-Universit¨at Mu¨nchen
zur Erlangung des Grades
Doktor der Naturwissenschaften
Dr. rer. nat.
vorgelegt von
Mario Schweitzer
aus Birkesdorf
Mu¨nchen, M¨arz 20082
1. Gutachter: Prof. Dr. Reinhard Genzel
2. Gutachter: Prof. Dr. Andreas Burkert
Datum der Einreichung: 27.03.2008
Datum der mu¨ndlichen Pru¨fung: 17.06.2008Contents
1 Summary / Zusammenfassung 7
I Optical Alignment and Characterization of FIFI LS 13
2 Introduction 15
2.1 Far-Infrared Astronomy . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 The Development of Airborne Astronomy . . . . . . . . . . . . . . 16
2.3 The SOFIA Observatory . . . . . . . . . . . . . . . . . . . . . . . 17
3 The Far-Infrared Spectrometer
FIFI-LS 19
3.1 Concept and Specification . . . . . . . . . . . . . . . . . . . . . . 19
3.2 Imaging 3D-Spectroscopy. . . . . . . . . . . . . . . . . . . . . . . 20
3.3 The Optical System . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.1 The Entrance Optics . . . . . . . . . . . . . . . . . . . . . 22
3.3.2 The Image Slicer Unit . . . . . . . . . . . . . . . . . . . . 25
3.3.3 The Exit Optics . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.4 The Calibration Optics . . . . . . . . . . . . . . . . . . . . 27
3.3.5 The Internal Calibration Source . . . . . . . . . . . . . . . 27
4 Optical Alignment 39
4.1 K-Mirror Alignment . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2 Long Wavelength Spectrometer Alignment . . . . . . . . . . . . . 41
4.2.1 Image Slicer Unit Alignment . . . . . . . . . . . . . . . . . 42
4.2.2 Spectrometer Optics Alignment . . . . . . . . . . . . . . . 43
4.2.3 Cold Test of the Optical Alignment . . . . . . . . . . . . . 47
5 The Telescope Simulator 51
5.1 Design and Alignment of the Telescope Simulator . . . . . . . . . 51
5.2 Preparation of the Telescope Simulator . . . . . . . . . . . . . . . 57
6 Characterizing FIFI-LS 61
6.1 Measuring the PSF . . . . . . . . . . . . . . . . . . . . . . . . . . 61
6.2 The Spectral Calibration . . . . . . . . . . . . . . . . . . . . . . . 66
6.3 The Spectral Resolution . . . . . . . . . . . . . . . . . . . . . . . 67
34 Contents
II AGN Studies with the Spitzer Space Telescope 71
7 Introduction 73
7.1 The Spitzer Space Telescope . . . . . . . . . . . . . . . . . . . . . 73
7.1.1 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . 74
7.2 Active Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
7.2.1 The AGN Unification Model . . . . . . . . . . . . . . . . . 77
7.3 The QUEST Project . . . . . . . . . . . . . . . . . . . . . . . . . 79
7.4 Data Reduction Tools . . . . . . . . . . . . . . . . . . . . . . . . 79
7.4.1 Removing Outlying Pixel Values . . . . . . . . . . . . . . . 80
7.4.2 Template Fitting . . . . . . . . . . . . . . . . . . . . . . . 81
8 Silicate Emissions in Active Galaxies - From LINERs to QSOs 83
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
8.2 Observations and Data Processing . . . . . . . . . . . . . . . . . . 84
8.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . 85
9 Extended Silicate Dust Emission in PG QSOs 91
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
9.2 The PG QSO Sample . . . . . . . . . . . . . . . . . . . . . . . . . 93
9.2.1 Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . 93
9.3 Modeling the PG QSO IRS Spectra . . . . . . . . . . . . . . . . . 95
9.3.1 Model Components . . . . . . . . . . . . . . . . . . . . . . 95
9.3.2 Fitting Procedure . . . . . . . . . . . . . . . . . . . . . . . 99
9.3.3 Cloud Distances and Covering Factors . . . . . . . . . . . 101
9.3.4 Fit Components and Uncertainties . . . . . . . . . . . . . 102
9.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
9.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
9.5.1 Dust Cloud Distances. . . . . . . . . . . . . . . . . . . . . 117
9.5.2 Covering Factors . . . . . . . . . . . . . . . . . . . . . . . 117
9.5.3 Silicate Emission and NLR Properties . . . . . . . . . . . . 118
9.5.4 Silicate Emission from Torus Models . . . . . . . . . . . . 119
9.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
10 Spitzer Quasar and ULIRG Evolution Study (QUEST):
I. The Origin of the Far Infrared Continuum of QSOs 123
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
10.2 The QUEST PG QSO Sample: Observations and Reduction . . . 126
10.2.1 The Sample . . . . . . . . . . . . . . . . . . . . . . . . . . 126
10.2.2 Data Reduction and Line and Continuum Measurements . 127
10.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
10.3.1 PAH Emission is Common in QSOs . . . . . . . . . . . . . 129
10.3.2 Trends with Level of PAH Emission . . . . . . . . . . . . . 132
10.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
10.4.1 NatureoftheQSOFar-InfraredEmissionandtheStarburst-
AGN Connection . . . . . . . . . . . . . . . . . . . . . . . 135Contents 5
10.4.2 Mid-infrared Diagnostics and the Starburst-AGN Connec-
tion in QSOs . . . . . . . . . . . . . . . . . . . . . . . . . 145
10.4.3 Direct AGN Heating of Cold Dust and PAHs ?. . . . . . . 148
10.4.4 Comparison to QSO Star Formation Estimates Based on
[OII] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
10.4.5 Implications for High Redshift QSOs . . . . . . . . . . . . 150
10.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
11 Conclusions 1536 ContentsChapter 1
Summary / Zusammenfassung
The best platforms for astronomical observations in the mid- and far-infrared
(FIR) wavelength regime are satellites which are used to collect scientific data
from outside the Earth’s atmosphere. Satellite observations are unaffected by
the atmospheric absorption and emission which prevent FIR observations from
theground. Infrared space telescopes like IRAS (Infrared Astronomical Satellite)
or ISO (Infrared Space Observatory) have been very successful missions in the
past and have led to the development of even more powerful space observato-
ries, like Spitzer (launched 2003) and Herschel (expected launch in late 2008).
One disadvantage of space observatories is, however, in addition to the enormous
technical and financial expenditure, that once the observatory is launched, there
is no possibility to maintain or update the observatory with new technologies.
In addition, the continuous loss of cryogenic liquids limits the operation time
of infrared space observatories on the long term (∼few years). Thus for follow
up observations, alternative platforms are needed. Therefore an airborne obser-
vatory, where a powerful wide-bodied aircraft carries a telescope into the lower
stratosphere, is an excellent extension to space observatories. Such a platform is
the NASA/DLR funded project SOFIA (Stratospheric Observatory for Infrared
Astronomy), expected to start its scientific operation in 2009.
The Max-Planck-Institute for Extraterrestrial Physics (MPE) has developed
one of the two German scientific instruments for SOFIA, the Far-Infrared Field
Imaging Line Spectrometer (FIFI-LS). This instrument allows one to acquire
spectral and spatial information simultaneously. Due to its high sensitivity and
observing efficiency, FIFI-LSwillbeused toinvestigatedistantsources, e.g. ultra
luminous infrared galaxies (ULIRGs), but it will also demonstrate its power as
an imaging spectrometer for nearby extended sources. The concept of integral
field spectroscopy in theFIRwasimplemented forthefirst time forFIFI-LSwith
an image slicer system based on mirror optics.
The first part of this thesis is related to FIFI-LS. In Chapter 2 the SOFIA
observatory is introduced. Chapter 3 presents the optical mode of operation of
FIFI-LS.Asanoutcomeofthiswork theopticaldesign oftheinternal calibration
source is presented in Chapter 3. Chapter 4 presents the optical alignment of the
long wavelength channel of FIFI-LS. To characterize the imaging and spectral
properties of the instrument in the FIR a telescope simulator was developed in
78 Chapter 1. Summary / Zusammenfassung
the context of this thesis. A description of this instrument is given in Chapter 5.
Finally Chapter 6 summarizes the characterization of FIFI-LS.
The second part of this work will present three publications related to MIR
observations of active galaxies obtained with the Infrared Spectrograph (IRS)
onboard of the Spitzer Space Telescope. The investigation of active galaxies in
theentirewaveband fromtheradiotothegamma-rayregimeisavery activefield
of modern astronomy that aims at an understanding of the physics of the active
galactic nucleus (AGN), its relation to star formation and the evolutionary pic-
ture of galaxies. In this context the mid-infrared wavelength range is especially
important, because in this region one can find AGN as well as starburst tracers.
This opens the possibility to disentangle the energy sources in activ