My research is focused on high-redshift quasars and the epoch of reionization (EoR). The EoR is a crucial milestone in cosmic history, during which the first galaxies ionized neutral hydrogen in the intergalactic medium, resulting in the diffuse plasma that we observe in the local Universe. Studying the EoR is important as it enables us to develop a full picture of the history of the Universe. Observations of the earliest sources also place important constraints on supermassive black hole growth mechanisms.
Quasars are extremely luminous sources and have been discovered at redshifts greater than 7. As the reionization epoch was ongoing until z~6, about 1Gyr after the Big Bang, high redshift quasars are extremely useful probes of this period in the Universe's history. However, very few z > 6.5 quasars have been discovered to date. I am currently working with Steve Warren & Daniel Mortlock to develop Bayesian model comparison techniques capable of identifying new high-redshift quasars in near-infrared surveys.
High redshift quasars are extremely rare, and searches for them in infrared surveys are strongly affected by contamination from M, L and T type stars in the Milky Way. Although dwarf stars and high-redshift quasars represent very different physical environments, they have similar colours at near-infrared wavelengths. Part of my research is therefore concerned with developing good models for these dwarf stars, which allows us to separate them from the target quasars more efficiently.
I completed my PhD at Imperial at the end of 2016. I was supervised by Steve Warren. My research was initially focused on the z = 7.084 quasar ULAS J1120+0641, the first quasar to be discovered with z > 7. I carried out detailed photometric and spectroscopic analyses of the quasar which were used to constrain properties of the source itself, and the environment along the line of sight towards it. I also began my current project, searching for new high-redshift quasars in the VIKING infrared survey.