Review Questions

1. In order to describe a single absorption line using a Voigt profile, how many parameters are required? What are these parameters (list and describe them)?

2. How is the expression for the optical depth of a Voigt profile for a single absorption line modified in order to describe a multi-component absorption profile using multiple Voigt profiles?

3. Say you have spectral coverage of multiple transitions from a given ion and you have generated the AOD column density profiles of each.  Your goal is to obtain the best possible AOD column density profile for the ion. What issues must you contend with and treat when constructing the AOD column density profile for an ion from the AOD column density profiles of its transitions?

4. Equivalent widths can be measured by fitting a Gaussian function to the absorption profile. Under what conditions is a Gaussian fit appropriate?  What two parameters from the fit are used to compute the equivalent width and what is the mathematical expression?  What caution must be taken when one is fitting an unresolved absorption line and how is that handled during the fitting process?

5. For blended absorption lines Gaussian profile decomposition can be undertaken. Compare and contrast Gaussian profile decomposition that simply minimizes the number of components in the fit and Gaussian profile decomposition that couples (or "ties") components that are doublets. 

6. For what conditions is fitting a Voigt profile to an absorption line profile appropriate?  When undertaking Voigt profile decomposition of a multi-component absorption profile, why might we aim to use as few Voigt profile components as possible to obtain a statistically sound fit? How might we ensure we have adopted the minimum number of significant components?

7. When undertaking Voigt profile decomposition of multi-component profiles of transitions from multiple ions, what are the three possible scenarios for treatment of the Doppler broadening of the components of the different ions? What are the science motivations for each?

8. What is a multiphase absorption system and what challenges does such a system pose for Voigt profile decomposition? Describe possible approaches to undertaking Voigt profile decomposition of multiphase multi-component absorbers.

9. What is a "fitting philosophy" and describe how it should align with science goals?

Problems

1. Under construction