Master Projects with Prof. Mertsch (2019-2020)
Project 1: Gamma-ray halos around pulsar wind nebulae
When massive stars die in violent supernova explosions, they leave behind a strongly magnetised neutron star. These can power so-called pulsar wind nebulae which shine brightly across the electromagnetic spectrum. Observations of high energy gamma-rays help us understand these fascinating sources and how they can possibly shed light on the mystery of cosmic ray positrons.
You will start by learning some fundamental plasma physics that determine the interplay between cosmic rays and magnetised turbulence. Next, you will build a model to connect the various pieces of information we have: cosmic ray protons, positrons and the gamma-ray emission from nearby and far-away pulsar winde nebulae. If the underlying idea is correct, this will decide a long-standing discussion in astroparticle physics.
Project 2: Dark matter searches in cosmic ray antiprotons
(jointly with Prof Kraemer)
Dark matter can be searched for by looking for anomalies in the fluxes of charged particles arriving at Earth, called cosmic rays. In fact, a number of anomalies have been found over the last couple of years in cosmic ray antiprotons. Before calling a discovery, however, alternative explanations need to be ruled out. In particular, we need to make sure that we understand the astrophysical production of antiprotons and their transport through the Galaxy.
In this project, you will learn how to look for dark matter in cosmic ray antiprotons. You will model both the contribution from dark matter and from astrophysical sources, also with a view to other fluxes of high-energy particles. You will update the parametrisations of the production cross-sections and for the transport of cosmic rays in the magnetised solar wind. In the end, we will be able to tell whether the dark matter signal persists.
Project 3: New statistical methods for Galactic diffuse emission
More than half of the photons of energies of 1 GeV and above cannot be attributed to individual sources, like pulsars, blazars or supernova remnants, but are diffuse, that is produced by the interstellar medium in the Galaxy. An important example is the excess of gamma-rays from the Galactic centre which has been speculated to be due to dark matter. Models of diffuse emission cannot model the Galaxy in all its complexity, but must make use of its statistical properties alone.
The underlying idea is that emission in one part of the Galaxy is related to emission in other parts of the Galaxy through correlations induced by turbulence. You will be applying a suite of new statistical techniques referred to as information field theories to better model this emission. This allows inferring more information from the data we have and maybe contribute a verdict as to the Galactic centre excess.