Contents

• Introduction to the ISO Long Wavelength Spectrometer
  • Introduction
  • Far-Infrared Observations
  • The ISO Long Wavelength Spectrometer
  • Operation of the LWS Instrument
    • Grating Operation
    • Fabry-Pérot Operation
  • Observing Modes
  • Non-Prime Data in Fabry-Pérot Mode
    • Non-Prime Data
    • Definition of Useful Non-Prime Data
  • Wavelength Calibration
    • Grating Wavelength Calibration
    • FP Wavelength Calibration
    • Effect of Grating Calibration on FP Data
  • The LWS Beam
    • The Mean Beam Profile
    • Correction for Extended Sources
    • Fringing and Spectrum Fracturing
  • The LWS Spectral Survey Programme
  • Summary
  
  
• Sagittarius B2 and its Line of Sight
  • Introduction
  • The Distance to the Galactic Centre
  • The Sagittarius B2 Complex
    • Source Structure
    • Physical Conditions in the Sgr B2 Complex
  • Velocity Structure Along the Line of Sight
    • The Sgr B2 Cloud and Envelope
    • Inner Regions of the Galactic Bar
    • Galactic Spiral Arms
  • Physical Conditions in the Line of Sight Clouds
  • Summary
  
  
• Flux Calibration of LWS FP Data
  • Observations of Sagittarius B2
    • Fabry-Pérot Observations
    • Velocity Correction
    • Grating Observations
  • Flux Calibration Strategy
  • Dark Current and Stray Light
    • Dedicated Dark Measurements
    • Dark and Stray Light Determination from Non-prime Data
  • Detector Responsivity
    • Standard Responsivity Correction
    • Responsivity Drift Correction
  • Recovery of Grating Response in FP Mode
    • Standard Grating Response Calibration
    • Contamination from Adjacent FP Orders and Strong Spectral Lines
    • Recovery of Profiles
    • Fitting the Profiles
  • Contamination from FP Side Orders
    • Checking for Order Contamination
    • Correcting for Order Contamination
    • Modelling the Fixed-FP Observations
    • Testing the FP Throughput Calibration
  • Data Processing Software
    • FP_PROC
    • Modifications to FP_PROC
    • Solutions Implemented
  • Remaining Calibration Problems
    • Detector Transient Effects
    • Extended Source and Off-Axis Correction
    • Data Reduction
  • Summary
  
  
• Overview of Results from the Survey
  • Introduction
  • Prime Data
    • Full Spectrum
    • Assigned Features
    • Unassigned Features
  • Non-Prime Data
    • Useful Data
    • FPL Above 70 $\mu$m
    • FPL Below 70 $\mu$m
  • Selected Line Examples
  • Summary
  
  
• Atomic Lines in the Spectrum of Sgr B2
  • Introduction
  • Observations
    • Prime Data
    • Non-Prime Observations
    • L04 Observations
  • Data Reduction and Calibration
    • Determination of Dark Current
    • Processing with FP_PROC
    • Removal of Glitches
    • Co-addition of Non-Prime Data
    • Processing of L04 Observations
  • Error Calculation
    • Signal to Noise
    • Systematic Errors
  • Standard PDR Model
  • External Cloud Layers
    • The HI 21 cm Line
    • The [CII] 157.7 $\mu$m Line and [OI] 145.5 $\mu$m Line
    • The [OI] 63 $\mu$m Absorption Components
  • Internal Molecular Cores
  • Summary
  
  
• Deuterium Abundance in the Sgr B2 Envelope
  • Introduction
  • Observations
  • Results
    • Line Fitting
    • Is the Feature Real?
  • HD Column Density
  • H$_2$ Column Density
    • Dust and Continuum Emission
    • SWS Observations of H$_2$ Rotational Lines
    • H$_{2}$ Results and Comparison with Previous Measurements
    • The Ortho-Para Transition in H$_{2}$
  • Deuterium Abundance
    • Calculation of D/H Ratio
    • Comparison with Models
  • Summary
  
  
• OH Absorption Towards Sgr B2
  • Introduction
    • Oxygen Isotope Variations in OH
    • Energy Levels of the OH Molecule
    • Laboratory Measurements
  • Observations of $^{16}$OH
  • Modelling of $^{16}$OH in the Line of Sight
    • High Resolution Model
    • Effect of Hyperfine Structure
    • Errors on the Fitted Parameters
    • Effect of Unresolved Components in HI
  • $^{18}$OH in the Line of Sight
    • Observations of $^{18}$OH
    • High Resolution Model
    • $^{16}$OH/$^{18}$OH Ratio
  • $^{17}$OH in the Line of Sight
    • Observations of $^{17}$OH
    • Predicting the Shape of the $^{17}$OH Absorption
    • Effect of Hyperfine Structure on Line Shape
  • Summary
  
  
• Conclusions and Future Work
  • Calibration and Data Reduction
  • Atomic Oxygen
  • Deuterium
  • Isotopic Abundance of Oxygen
  • Future Work
    • Line of Sight Modelling
    • Weak Features
    • Unassigned Lines
    • Future Instrumentation
  
  
• Raw Data
• L04 Observations
• Grating Observations
• Reduced Prime Data
• Unassigned Features
• Bibliography
• About this document ...