Probing galaxies with quasar absorption lines

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Distant quasars (also sometimes called QSOs) can be used as lighthouses at the edge of the universe to study galaxies that lie between them and the Earth. My research focuses on using the imprints of intervening galaxies on the spectra of quasars to study their formation and evolution. Whilst this technique is several decades old, my research is finding novel applications of the idea. For example, my team has perfected a technique for finding rare cases where the background QSO probes highly metal-enriched regions of an intervening galaxy. These sight lines are also expected to be rich in molecules which we can use to model the physical characteristics of the galaxy and even trace evolution of fundamental constants with time. In very extreme cases, we can even see the signatures of organic compounds and we have recently made the first detection of such features at cosmological distances.