ISM has been swept-up by the disc at any moment in time, we need to differentiate between the disc and the ISM flow. This is not straightforward since there is no clear separation between the outer edge of the disc and the flow. In order to distinguish between the disc and the ISM flow, we use a clump finding algorithm to identify different groups in the parameter space of the angular speed ($v_{\theta}$), the density ($\rho$) and the speed along the axis of the cylinder($v_x$) of each particle. In this parameter space, we expect the ISM particles to cluster around values of, respectively, 0 km/s, $\rho_{\rm ISM}$ and $v_{\rm ISM}$, while the disc particles will not. For the clump finding algorithm we use Hop [@eisenstein98].

Fig. \[fig:disc\_recognition\_eda1a\] shows a comparison of how well this algorithm (solid black line) performs for our reference model compared to drawing a coaxial cylinder around the disc, with a length of 100 AU and a radius of 120 AU, and adding the mass of all the SPH-particles in that volume (dotted black line). The difference between these two lines can be attributed almost completely to the ISM that is in the volume, but not part 