Sadik Acili MSc defense

Title: A galaxy illuminated by a GRB at z=2.33

Supervisor: Johan P.U. Fynbo, DARK/NBI
Censor: Jérôme Chenevez/DTU

Abstract: This thesis is about the detection and analysis of a Gamma-Ray-Burst event taking place at a redshift of z=2:33. The absorption-lines of the intervening galactic system is easily identi ed and their characteristics enables us to calculate some of the host-galaxy properties, such as the redshift, column densities and metallicities - one of the only ways possible using Gamma-Ray-Bursts as cosmological host-galaxy probes.

Chapter 1 is a brief introduction to Gamma-Ray-Bursts and their discovery, origin, progenitors and what they can do for us, along with a brief description of how to interpret the absorption-lines, how to measure the column densities and deploy the curve-growth- method to infer host-galaxy properties. Basically; showing what we can infer from a GRB spectrum.

A description and introduction to some key elements in our understanding of the Universe which we live in, will be presented in Chapter 2, starting with the Big Bang and the onset of the primordial nucleosynthesis, through the epoch of recombination, the radiation, matter and dark-energy dominated eras, all the way up to the formation of structure and what we can observe today. This chapter will hopefully form the framework in which we understand GRB's in a cosmological setting.

Chapter 3 is an introduction to spectral analysis, how to interpret the equivalent widths of an absorption line and relate it to the di erent optical regimes in a curve-of-growth analysis. The formulas behind the IDL- tting procedures are outlined. In Chapter 4 I will present the obtained data and the analysis including identifications of the host-galaxy atomic lines, column-densities and the metallicity of the host-galaxy. It turns out, the extremely bright oxygen emission-line from the host-galaxy itself is also present in the spectrum. This will be showed.

In the final Chapter 5 I will conclude and discuss my work comparing it with other high-redshift GRB studies and determine whether the obtained metallicities fits within the uncertainties in these other works. A full-scale chi² error-analyzation lies outside the scope of my thesis, but still a simple and somewhat crude error-margin to the metallicity can be given.