common practice to define hard boundaries in CMDs [see e.g. @2012MNRAS.422.1495L]. Including non-informative variables may also dilute the discriminative power of relevant ones, thus leading to poor performances. We explored several representation spaces and assessed their relative merits.

As shown in Table \[nrofmeas\], 89% and 79% of the sources do not have measurements in the u and g bands, respectively. We excluded these two bands to avoid creating initial models of the member and field samples composed exclusively of bright, relatively hot objects.

We assessed a number of representation spaces summarised in Table \[repspaces\].

  Experiment                 Representation space
  -------------------------- ----------------------------------------------------------------------------
  Apparent Magnitudes (AM)   $\mu_{\alpha}$ $\mu_{\delta}$, r, i, J, H, K, Y, Z
  Colour indices 1 (CI-1)    $\mu_{\alpha}$ $\mu_{\delta}$, (r-i), (i-Z), (Z-Y), (Y-J), (J-H), (H-K)
  Colour indices 2 (CI-2)    $\mu_{\alpha}$ $\mu_{\delta}$, (i-J), (i-K), (Y-J), (Z-J), (r-H), (r-K)
  r + CI-2                   $\mu_{\alpha}$ $\mu_{\delta}$, r, (i-J), (i-K), (Y-J), (Z-J), (r-H), (r-K)
  i + CI-2                   $\mu_{\alpha}$ $\mu_{\delta}$, i, (i-J), (i-K), (Y-J), (Z-J), (r-H), (r-K)
  K + CI-2                   $\mu_{\alpha}$ $\mu_{\delta}$, K, (i-J), (i-K), (Y-J), (Z-J), (r-H), (r-K)
  RF-1                       $\mu_{\alpha}$ $\mu_{\delta}$, r, J, H, K, (i-J), (r-K)
  RF-2                       $\mu_{\alpha}$ $\mu_{\delta}$, J, H, K, (i-K), (r-K), (Y-J)
  RF-3                       $\mu_{\alpha}$ $\mu_{\delta}$, J, H, K, Y, (i-Z), (r-Y), (r-i)

The 