MUSE reveals metal-enriched absorbers in the CGM of a radio galaxy at z=2.9

There can be no complete discussion of the ``cosmic noon" epoch and early galaxy formation without referencing radio galaxies existing at redshifts, z $>$ 2. Known to be the most massive galaxies in terms of stellar mass, high-redshift radio galaxies (HzRGs) are often surrounded by large haloes extending beyond 100 kpc into the CGM. Previous studies of the CGM were mostly restricted to bright emission lines, which sometimes also show the presence of absorbing gas in the CGM. With the advent of sensitive integral field unit instruments such as MUSE, spatially resolved studies of UV ionised gas tracers (Ly$\alpha$, CIV, HeII) in these sources are now possible. In this talk, I will present recent MUSE results that reveal the first detection of NV absorption in the same gas volume as HI and CIV in diffuse, low-density absorbing gas located in the nebulae of a z=2.9 radio galaxy. We show that these metal-enriched absorbers are associated with the galaxy rather than being intervening systems. From the same MUSE data, we have also been able to trace the spatial extent of the Ly$\alpha$ nebulae in absorption i.e. neutral HI medium and thus measure its mass. Using CLOUDY photoionisation models, we investigate the possible ionising mechanisms for the absorbers and their probable origins within this galaxy's evolutionary sequence. Studies like ours thus open up a new window on the metal-enriched CGM.