Thesis Topic: Probing the metallicity distribution of the Circumgalactic Medium down to unprecedented scales

Thesis Supervisors:


We have now mounting evidences that the circum-galactic medium (CGM) of galaxies is polluted with metals processed through stars. The fate of these metals is however still an open question and several findings indicate that they remain poorly mixed. Important issues thus remain unsolved: On which scales are metals mixed? How does it vary with environment (i.e. IGM vs. CGM)? Where are the high-metallicity, intergalactic gas clouds?

A powerful tool to study this low-density gas is offered by absorption lines in quasar spectra. However, the brightest background sources (quasars and GRBs) are point-sources so that the observer is limited to the information gained along the line-of-sight. On the contrary, by using an extended galaxy as background source combined with 3D spectroscopy, one can directly map the distribution and sizes of the metal clouds on small scales. The PhD project will use a new dataset from a recently awarded VLT/MUSE programme. The MUSE observations allow us for the first time to probe the gas spatially on kpc-scales in the plane of the sky over a continuous area. We will then measure the metal cloud sizes which, combined with our knowledge of the gas densities, will constrain the cloud gas mass. Ultimately, this will allow us to quantify the efficiency of the metal mixing on scales never probed before. In the future, such studies can be extended to numerous bright galaxies up to the highest redshifts observables with JWST and ELT/HARMONI.

The project is part of an international 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.


Péroux, C.; Rahmani, H.; Arrigoni Battaia, F.; Augustin, R. "Spatially resolved metal gas clouds", 2018MNRAS.479L..50