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A prediction of the classic active galactic nuclei (AGN) unification model isthe presence of ionisation cones with different orientations depending on theAGN type. Confirmations of this model exist for present times, but it is lessclear in the early Universe. Here, we use the morphology of giant Ly$\alpha$nebulae around AGNs at redshift z$\sim$3 to probe AGN emission and thereforethe validity of the AGN unification model at this redshift. We compare thespatial morphology of 19 nebulae previously found around type I AGNs with a newsample of 4 Ly$\alpha$ nebulae detected around type II AGNs. Using twoindependent techniques, we find that nebulae around type II AGNs are moreasymmetric than around type I, at least at radial distances $r>30$~physical kpc(pkpc) from the ionizing source. We conclude that the type I and type II AGNsin our sample show evidence of different surrounding ionising geometries. Thissuggests that the classical AGN unification model is also valid forhigh-redshift sources. Finally, we discuss how the lack of asymmetry in theinner parts (r$\lesssim$30 pkpc) and the associated high values of the HeII toLy$\alpha$ ratios in these regions could indicate additional sources of (hard)ionizing radiation originating within or in proximity of the AGN host galaxies.This work demonstrates that the morphologies of giant Ly$\alpha$ nebulae can beused to understand and study the geometry of high redshift AGNs oncircum-nuclear scales and it lays the foundation for future studies using muchlarger statistical samples.

Probing the AGN Unification Model at redshift z $\sim$ 3 with MUSE observations of giant Ly$\alpha$ nebulae