Master thesis by Malte Brinch

Title: Reverberation mapping of nearby Seyfert galaxies for cosmology. Determining the dust torus time lag

Abstract:
There is currently a dispute as to the true value of the Hubble constant. The discrepancy is mainly between the value determined by the Planck collaboration using the Cosmic Microwave background and the value determined by using the traditional distance ladder by measuring type Ia supernovas in the local universe. The idea of this project is to determine an intermediary value for the Hubble constant that can corroborate either of the other values or perhaps hint at undiscovered physics. The idea behind this project is to determine the lag of the dusty torus in AGN, so that it can be used to determine the absolute distance to the object. The data to do this reverberation mapping will be from the Rapid Eye Mount telescope at the La Silla Observatory in Chile. The data is from the 3 J,H,K Near Infra Red filters and the 4 g,r,i,z optical filters. The main focus of this project is to create an algorithm that perform photometric reverberation mapping analysis using the 7 light curves without having any data for the driving light curve that drives the response seen in the observed data. The focus is on creating code that reliably and with reasonable compute time that determine the lag to the torus. To set up such an algorithm background knowledge of the structure of AGN and the mathematical models used to describe their light curves is presented. to efficiently determine the lag, a state of the art Markov Chain Monte Carlo Sampler is used and the setup for such a sampler is discussed. To test the reverberation mapping model a script is created that can create synthetic light curves to test the model. While the model was able to recover the lag with some uncertainty using the synthetic data, the model failed to work on data from actual AGN. The reason as to why this might be the case are discussed. It is concluded that more work needs to be done to understand the specific form of the transfer function used in the model and that the scatter in the light curves might hinder the determination of the lag.

Supervisor
Darach Jafar Watson, NBI, DAWN

Censor
 Jérôme Chenevez, DTU.