Characterising the Gravitationally Lensed Quasar Population

Abstract

Understanding the co-evolution of quasars and their host galaxies remains one of astronomy's biggest questions. Observing the quasar and its host galaxy at low redshifts is relatively straightforward. However, this becomes more complex at higher redshifts. One method to study this co-evolution is to use gravitationally lensed quasars which separates the light from the quasar from the host galaxy light, making it a perfect tool to study this co-evolution at higher redshifts. In the last decade, the number of gravitational lenses has increased to $\sim$ 400. However, the current state of the gravitationally lensed quasar catalogue is a compilation of several different heterogeneous studies. To study subsets of different populations of lensed quasars we first need a homogeneous catalogue of lensed quasar properties. This thesis aims to create a homogeneous gravitationally lensed quasar catalogue containing photometric, spectroscopic and lens modelling properties which will be an asset to the community. By using Pan-STARRS and our in-house photometry pipeline, we were able to model $\sim$ 200 gravitationally lensed quasar systems to obtain astrometry and multi-band photometry. We were then able to take the astrometry and model the lenses which resulted in us being able to determine the magnifications and model time delays. We were also able to combine the magnifications with the photometry and wwere able to infer intrinsic monochromatic L${1350}$ and L${3000}$. We obtained spectra from SDSS, EFOSC2 and ISIS to fit models to the C\textsc{IV} and Mg\textsc{II} emission lines and surrounding continuum to obtain velocity widths for a total of 142 lensed quasars. We were able to combine the intrinsic monochromatic luminosities and velocity widths to obtain SMBH masses for 66 gravitationally lensed quasars, an increase of 33 from previous studies. This has led to the first homogeneous catalogue of gravitationally lensed quasars. This is just the start as we looked at all possible lenses despite knowing that some objects would not have useable spectra or photometry as many of the spectra lie outside of the Pan-STARRS footprint.