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tokens: have been active for . The projection has a depth of and is centred on the BH. This disc galaxy provides the initial conditions for simulations with a disc galaxy in an NFW halo. In the left-hand panel of Fig. 12 , we plot the mass of the baryonic components, i.e. gas, stars, metals, and dust, of the halo with r 200 as a function of time. After , a stellar disc with a mass has formed in the xy plane of the halo with a radial extent of . Over the first , a dust mass rapidly forms, after which the dust mass grows much more slowly and the final halo has a dust mass . The build-up of gaseous metals initially occurs at a slower rate, but after the dust and metal content of the halo is roughly similar, with a cumulative dust-to-metal ratio of 1.15 within r 200 . Figure 12. Properties of the initial disc galaxy. Left : Gas (red solid), stellar (blue dash–dotted–dotted), metal (purple dash–dotted), and dust (pink dashed) mass components with r 200, crit . The global halo properties are reasonable for a disc galaxy. Centre : Radial dust mass surface density profile for the relaxed NFW halo with D = 0.01 (blue dash–dotted–dotted), the NFW halo with a disc galaxy and D = 0.01 (light purple dash–dashed), and the NFW halo with a disc galaxy and self-consistently modelled dust (red solid). Right : Dust-to-gas ratio radial profile as a function of time for the NFW halo with a central disc galaxy and self-consistently modelled dust. We plot t = 0.5 (blue dash–dotted–dotted), 1.0 (purple dash–dotted), 1.5 (light purple dash–dashed), 2.0 (pink dashed), and (red solid). Dust is confined to the disc due to the lack of feedback and satellite mergers during its formation. The formation of the disc galaxy leads to a contraction of the halo. The central panel of Fig. 12 shows the radial dust surface density profile, where the halo has been projected along the z -axis of the simulation (i.e. the galaxy is face on). For the initial NFW halo with a constant dust-to-gas ratio D = 0.01, the surface density of the dust decreases strongly with radius from at to 5 × 10 −4 at r 200 . After the formation of the disc, still assuming D = 0.01, central dust surface density of dust at increases to . However, due to material condensing to form the disc galaxy the dust surface density is lower than the initial NFW halo beyond . Modelling the formation of dust we find that its central surface density increases still further, reaching a dust surface density of at . The lack of feedback during the formation of the disc galaxy means that we achieve higher than typically observed central dust densities. In addition, the idealized nature of the simulation results in the circumgalactic medium (CGM) of the halo being free from dust because dust is not produced in the CGM but instead is acquired through in-falling satellites. The evolution of the dust-to-gas ratio radial profile during the formation of the disc galaxy is shown in the right-hand panel of Fig. 12 . The dust initial forms in a