Master’s Thesis Defence by Nicolas Tschorn Rasmussen

Title: Examining the 2175Å feature in galactic and extragalactic extinction curves

Abstract: This project examines the presence of the 2175Å extinction feature from interstellar dust in galaxies beyond the Milky Way.

Galactic interstellar extinction curves reveal physical properties of the dust lying in the sight-line between the object and the observer. Stecher (1965) was the first to discover the dominant 2175Å absorption feature by studying the extinction curves of stars in the Milky Way.

Over the past decades the dominant spectral feature has furthermore been detected in the spectra of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) (e.g. Draine (2011)), as well as in the spectra of quasars (e.g. Jiang et al. (2011)), and Gamma-Ray Burst (GRB) (e.g. Zafar et al. (2018)).

The aim of this project is to create a coding tool that can analyze and determine if the 2175Å bump is present in observations by European Southern Observatory (ESO)’s X-Shooter instrument, and the strength and shape of the bump when present. If all the dust compositions are similar, the absorption might be caused by the same carrier.