Deprojection of the product (black points), compared with the total luminosity PDF of IGPC pairs (blue histogram). The product of 3D variables rv² gives the total mass of the pair (in the circular orbit approximation). The resulting mass has been translated into luminosity through a constant M/L ratio. The red line results from a numerical simulation that facilitates settling the uncertainty of the deprojection (two black lines, ±1 sigma). The luminosity PDF falls within ≈ one sigma of the deprojected points, allowing the derivation of a mass over luminosity ratio of M/L = 30 ± 5.