Optical 3D-spectroscopy for astronomy

242 Pages·2017·8.294 MB·English

by  Roland Bacon, Guy Monnet

Optical3D-SpectroscopyforAstronomy
Optical 3D-Spectroscopy for Astronomy
RolandBaconandGuyMonnet
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v
Contents
Foreword xi
Acknowledgments xiii
TheEmergenceof3DSpectroscopyinAstronomy 1
ScientificRationale 1
3DHistory 4
3DTechnology 9
PartI 3DInstrumentation 11
1 TheSpectroscopicToolbox 13
1.1 Introduction 13
1.1.1 GeometricalOptics#101 13
1.1.2 EtendueConservation 15
1.2 BasicSpectroscopicPrinciples 18
1.2.1 TheSpectroscopicCase 18
1.3 ScanningFilters 20
1.3.1 Introduction 20
1.3.2 InterferenceFilters 22
1.3.3 Fabry–PérotFilter 24
1.4 Dispersers 25
1.4.1 Prisms 25
1.4.2 GratingPrinciple 27
1.4.3 TheGratingSpectrograph 28
1.4.4 GratingSpecies 29
1.4.5 GratingEtendue 30
1.4.6 Conclusion 31
1.5 2DDetectors 31
1.5.1 Introduction 31
1.5.2 ThePhotographicPlate 32
1.5.3 2DOpticalDetectors 32
1.5.4 2DInfraredArrays 35
1.5.5 Conclusion 35
vi Contents
1.6 OpticsandCoatings 36
1.6.1 IntroductiontoOptics 36
1.6.2 OpticalComputation 37
1.6.3 OpticalFabrication 40
1.6.4 Anti-ReflectionCoatings 42
1.6.5 HighReflectivityCoatings 43
1.6.6 Conclusions 44
1.7 Mechanics,CryogenicsandElectronics 45
1.7.1 MechanicalDesign 45
1.7.2 Alignments 48
1.7.3 Cryogenics 48
1.7.4 ElectronicsandControlSystem 49
1.8 Management,Timeline,andCost 50
1.9 Conclusion 52
2 MultiobjectSpectroscopy 61
2.1 Introduction 61
2.1.1 MOSHistory:ThePioneers 61
2.1.2 MOSHistory:TheDigitalAge 62
2.1.3 MOSFlavors 62
2.2 SlitlessBasedMulti-ObjectSpectroscopy 62
2.2.1 SlitlessSpectroscopyConcept 62
2.2.2 SlitlessSpectroscopicSystems 64
2.3 Multislit-BasedMultiobjectSpectroscopy 64
2.3.1 MultislitConcept 64
2.3.2 MultislitHolders 66
2.3.3 MultislitSystems 69
2.3.4 MultislitInstruments 70
2.4 Fiber-BasedMultiobjectSpectroscopy 70
2.4.1 MultifiberConcept 70
2.4.2 PositioningSystems 71
2.4.3 Fiber-BasedSpectrograph 75
2.4.4 FiberSystemsPerformance 75
2.4.5 PresentMultifiberFacilities 76
2.4.6 Conclusion 77
3 ScanningImagingSpectroscopy 81
3.1 Introduction 81
3.2 ScanningLong-SlitSpectroscopy 81
3.2.1 TheScanningLong-SlitSpectroscopyConcept 81
3.2.2 AstronomicalUse 82
3.3 ScanningFabry–PérotSpectroscopy 83
3.3.1 Introduction 83
3.3.2 FixedFabry–PérotConcept 83
3.3.3 ScanningFabry–Pérot 85
3.4 ScanningFourierTransformSpectroscopy 88
3.4.1 FourierTransformSpectrometer 88
Contents vii
3.4.2 FourierTransformSpectrograph 90
3.5 Conclusion:ComparingtheDifferentScanningFlavors 91
4 IntegralFieldSpectroscopy 95
4.1 Introduction 95
4.2 Lenslet-BasedIntegralFieldSpectrometer 95
4.3 Fiber-BasedIntegralFieldSpectrometer 102
4.3.1 TheFiber-BasedIFSConcept 102
4.3.2 TheFiber-BasedIFSDevelopment 103
4.3.3 Conclusion 103
4.4 Slicer-BasedIntegralFieldSpectrograph 104
4.4.1 Introduction 104
4.4.2 IntegralFieldSpectroscopyfromSpace 107
4.5 Conclusion:ComparingtheDifferentIFSFlavors 108
5 RecentTrendsinIntegralFieldSpectroscopy 115
5.1 Introduction 115
5.2 High-ContrastIntegralFieldSpectrometer 115
5.2.1 ExoplanetDetection 115
5.2.2 High-ContrastIntegralFieldSpectrometer 116
5.3 Wide-FieldIntegralFieldSpectroscopy 117
5.3.1 TheRationaleforWide-FieldIntegralFieldSpectroscopy 117
5.3.2 CurrentWide-FieldProjects 117
5.3.3 Wide-FieldSystems3DFormat 119
5.4 AnExample:AutopsyoftheMUSEWide-FieldInstrument 120
5.4.1 MUSEConcept 120
5.4.2 MUSEApproach 120
5.4.3 MUSEConclusions 122
5.4.4 ValidityoftheMulti-instrumentApproach 123
5.5 DeployableMultiobjectIntegralFieldSpectroscopy 123
5.5.1 Concept 123
5.5.2 TheFirstDeployableIntegralFieldUnitsSystem 124
5.5.3 NearInfra-RedDeployableIntegralFieldUnits 124
5.5.4 DeployableMulti-IntegralFieldSystems:Conclusion 126
6 ComparingtheVarious3DTechniques 129
6.1 Introduction 129
6.2 3DSpectroscopyGraspInvariantPrinciple 129
6.3 3-DTechniquesPracticalDifferences 130
6.3.1 PackingEfficiency 130
6.3.2 ObservationalEfficiency 131
6.4 ATentativeRating 133
7 FutureTrendsin3DSpectroscopy 137
7.1 3DInstrumentationfortheELTs 137
7.2 Photonics-BasedSpectrograph 138
viii Contents
7.2.1 OHSuppressionFilter 138
7.2.2 PhotonicsDispersers 141
7.2.3 PhotonicsFourierTransformSpectrometer 141
7.2.4 Analysis 142
7.3 QuestfortheGrail:Toward3DDetectors? 144
7.3.1 Introduction 144
7.3.2 Photon-Counting3DDetectors 144
7.3.3 Integrating3DDetector 145
7.4 Conclusion 146
7.5 ForFurtherReading 146
PartII Using3DSpectroscopy 151
8 DataProperties 153
8.1 Introduction 153
8.2 DataSamplingandResolution 153
8.2.1 SpatialSamplingandResolution 154
8.2.2 SpectralSamplingandResolution 155
8.3 NoiseProperties 158
9 ImpactofAtmosphere 167
9.1 Introduction 167
9.2 BasicSeeingPrinciples 168
9.2.1 WhatisAstronomicalSeeing? 168
9.2.2 SeeingProperties 170
9.3 Seeing-LimitedObservations 172
9.3.1 SeeingImpacton3DInstruments 172
9.4 AdaptiveOpticsCorrectedObservations 173
9.4.1 TheNeedforOvercomingAtmosphericTurbulence 173
9.4.2 AdaptiveOpticsCorrectionPrinciple 173
9.4.3 AdaptiveOpticsComponents 176
9.4.4 AdaptiveOptics:TheOpticalDomainCurse 178
9.4.5 AddressingtheLackofReferenceStars 179
9.4.6 AddressingtheSmallFieldLimitation 182
9.4.7 LargeFieldPartialAOCorrection 183
9.4.8 AO-BasedScanningInterferometers 184
9.4.9 AO-BasedSlitSpectrographs 185
9.4.10 AO-BasedIntegralFieldSpectrographs 185
9.4.11 AO-BasedNear-IRMultiobjectIntegralFieldSpectrographs 187
9.4.12 DerivingAO-CorrectedPoint-SpreadFunctions 188
9.4.13 Conclusion 188
9.4.14 ForFurtherReading 189
9.5 OtherAtmosphereImpacts 189
9.5.1 AtmosphericExtinction 189
9.5.2 AtmosphericRefraction 189
Contents ix
9.5.3 NightSkyEmission 191
9.6 Space-BasedObservations 192
9.6.1 TheCaseforSpace-BasedObservations 192
9.6.2 WhyallTelescopesarenotSpaceTelescopes 193
9.7 Conclusion 194
10 DataGathering 199
10.1 Introduction 199
10.2 PlanningObservations 199
10.3 EstimatingObservingTime 200
10.4 ObservingStrategy 204
10.5 AttheTelescope 206
10.6 Conclusion 209
11 DataReduction 213
11.1 Introduction 213
11.2 Basics 214
11.3 SpecificCases 216
11.3.1 SlitlessMultiobjectSpectrograph 216
11.3.2 ScanningFabry–PérotSpectrograph 216
11.3.3 ScanningFourierTransformSpectrograph 217
11.3.4 GettingNoiseVarianceEstimation 217
11.3.5 MinimizingSystematics 218
11.4 DataReductionExample:TheMUSEScheme 219
11.4.1 DetectorCalibration 221
11.4.2 Flat-FieldCalibrationsandTraceMask 222
11.4.3 WavelengthCalibrations 224
11.4.4 GeometricalCalibration 225
11.4.5 BasicScienceExtractionandPixelTables 226
11.4.6 DifferentialAtmosphericCorrection 226
11.4.7 SkySubtraction 228
11.4.8 SpectrophotometricandAstrometricCalibrations 229
11.4.9 Data-CubeCreation 232
11.4.10 DataQuality 233
11.5 Conclusion 236
12 DataAnalysis 237
12.1 Introduction 237
12.2 HandlingDataCubes 237
12.2.1 TheSpectralView 238
12.2.2 TheSpatialView 239
12.2.3 The3DView 239
12.3 ViewingDataCubes 240
12.4 Conclusion 241
12.5 FurtherReading 243
x Contents
13 Conclusions 245
13.1 Conclusions 245
13.2 General-UseInstruments 245
13.3 Team-UseInstruments 250
13.4 TheBumpyRoadtoSuccess 251
References 253
Index 269
xi
Foreword
The development of astronomy has gone hand in hand with advances in tech-
nology.AcelebratedstepwastakenbyGalileoGalileiin1609whenheusedthe
newlyinventedtelescopetoobservethenightskyanddiscoveredmountainson
the Moon, the phases of Venus, and four moons orbiting Jupiter. This revolu-
tionizedourworldview,andwasmadepossiblebytheincreasedlight-gathering
power and image sharpness provided by the 5cm telescope lens compared to
usingthenakedeye.
Since then, a number of such transformational steps enabled by new tech-
nology have occurred. The move from the lenses of refracting telescopes to
the mirrors of reflecting telescopes allowed those telescopes to be of much
largerdiameter.Replacingthehumaneyeasthedetectorbehindthetelescope,
first with photographic plates and subsequently with almost perfectly sensitive
electronic detectors, made it possible to collect light over time and hence
observe much fainter objects. Dispersing the light into a spectrum revealed
the physical nature of objects through the study of absorption and emission
lines.Thedetectionofinfraredlightandradiowavesfromthegroundexpanded
astronomers’ view beyond the wavelengths of visible light, and the launch of
telescopesintospacegaveaccesstotheentireelectromagneticspectrum.With
the ability to detect particles and, most recently, gravitational waves emitted
by celestial objects, astronomers now have even more ways of observing the
Universe.
Spectroscopyintheopticalandnear-infraredregionswasinitiallypossiblewith
a single aperture, which was adequate for observing stars. The development of
spectroscopywithaslitallowedamoreefficientstudyofextendedobjectsand,
morerecently,theabilitytoperformspectroscopyoveranextendedareahasonce
again provided an enormous jump in capabilities. This latest revolution is the
topic of this book. The techniques for integral-field spectroscopy in the visual
andinfraredwavelengthregionhavenowmaturedtoalevelwheretheangular
resolution of the spectroscopic observations can be as high as is achievable in
directimaging,andmanytelescopeshavebeenequippedwithsuchintegral-field
spectrographs,withothersunderdevelopmentforthenextgenerationofgiant
telescopes.Acomprehensiveoverviewishencetimely.
Theauthorsareworld-renownedexpertswhohavehadamajorroleindriving
the development of integral-field spectroscopy from initial prototypes such as
TIGER on the Canada France Hawaii Telescope and SAURON on the William