Thesis Topic: Characterising the Physical Conditions of the Circumgalactic Medium


Thesis Supervisor: Celine Peroux and Martin Zwaan


Baryons from the cosmic web accrete onto galaxies, cool into a dense neutral then a molecular phase which fuels star formation, expelling material from these galaxies in powerful outflows which transform the surrounding circumgalactic medium (CGM). Today, the lack of observational constraints limits our understanding and our capacity to simulate this so-called baryon cycle. Quasar absorption features associated with foreground galaxies provide a unique tool to probe the gas properties of galaxies. The main advantage of absorption over emission from galaxies is the ability to reach low gas densities. To establish the connection of the circumgalactic medium gas probed to the underlying galaxy, it is essential to complement the absorption spectroscopy with imaging of the galaxies. A powerful technique is 3D spectroscopy.

The project will use a dataset already in hand from the MUSE 3D spectrograph on the Very Large Telescope (VLT) in Chile. We have carefully selected targets from HST spectroscopy to cover prominent emission lines with MUSE. The observations will provide impact parameter, star formation rate, metallicity, and kinematics of a statistical sample an order of magnitude larger than any other currently available at any redshift. Furthermore, we have secured mm ALMA observations of similar fields to measure the molecular masses, velocity fields and star formation efficiencies of the sources detected in CO. These observations are ideal to relate the neutral atomic gas, molecular gas and stars in the same objects resulting in a full baryon census of complex galaxy structures. This ambitious survey will help solve a major unknown in current galaxy evolution models: the physical conditions of the circumgalactic medium.

The project is part of a team effort to study the cosmic baryon cycle through multi-wavelength observations and simulations of galaxies. The student will be part of a large team of scientists with a huge accumulated experience on studies of galaxy evolution.