DES/DECam follow-ups of Gravitational Wave events

ith the advent of the LIGO/Virgo network of gravitational wave detectors, we have successfully detected gravitational waves (GWs) produced during compact object inspirals. This has enabled us to inspect the Universe using a completely new probe. One of the GW events detected, GW170817, is understood to be the result of a binary neutron star (BNS) merger in the galaxy NGC4993. This was a multi-messenger event as the Dark Energy Survey Camera (DECam) (and other collaborations) detected an electromagnetic signal accompanying the gravitational wave detection. This detection alone has led to exciting discoveries in the field of physics. The PhD project is split into three main parts. Initially the aim is to search for optical flashes from future LIGO/Virgo alerts as part of the DES/DECam team. About one GW event per month is expected, so there is a real-time element to the project, with exciting unexpected discoveries. This part will involve advanced image processing methods on very large data sets. Once a long list of optical candidates is selected, a range of machine learning and Bayesian approaches will be implemented to assign probabilities to the most likely GW host galaxy. This is a 'finding a needle in a haystack' problem. For example, in the case of the DES/DECam follow-up of GW170817 there was a down-selection from 1,500 candidates to the 'real' one. Finally, a catalogue of all shell galaxies in DES will be created, by comparing images to templates of simulated shell galaxies which will facilitate to test whether BNS are more likely to be formed as a result of a galaxy merger. This hypothesis will be tested by cross correlating the shell galaxies with X-ray, Gamma-ray and GW events and comparing the frequency of events with other non-shell galaxies. Other outcomes of this project include improved measurements of the Hubble constant using GWs.