Thesis topic: A multi-phase study of the Circum Galactic Medium in High-z radio galaxies with ALMA and MUSE

Thesis Supervisors: Joël Daniel Roger Vernet and Carlos De Breuck


Radio galaxies (obscured type II AGN) are among the most massive and luminous galaxies known at any redshift. They are the ideal signposts to find proto-clusters. Since the 1990s, it is known that they are surrounded by massive haloes extending to 150-200 kpc. With the advent of MUSE on the VLT, such haloes are now also found around quasars (unobscured type I AGN), but these do show clear differences: (i) the radio galaxy haloes are clearly influenced by the central AGN in the form of (often asymmetrical) ionization cones; (ii) we observe strong emission (e.g. from H2O) coincident with bends of the radio jets; and (iii) the smaller radio sources tend to show more associated absorbers in their Ly-alpha and CIV profiles.

These emission-line haloes extend well beyond the boundaries of the host galaxy, and form the link between its inter-stellar medium and the intra-cluster gas in the proto-cluster environment, i.e. the Circum Galactic Medium (CGM). They may well represent the accretion flows feeding the host galaxies with primordial gas from filamentary large-scale structures. The AGN is the flashlight illuminating and revealing these structures which play a crucial role in the galaxy formation process.

The overall goal of this PhD is to obtain a complete picture of these complex physical processes. To achieve this, you will study the constituents of the haloes in all possible phases: ionized, molecular, atomic, neutral. The work will focus on a sample of 8 radio galaxies at 2.9<z<4.5 observed with both VLT/MUSE and ALMA. All data are at hand. The MUSE data reveal the ionized and neutral gas, while the ALMA [CI] data trace the molecular and atomic gas, as well as star-forming regions (by means of the dust continuum).