Lyα (black), 2γ (red), Hα (green), Hβ (blue), He ii 1640 Å (orange) luminosities over their predicted case B luminosities for the primordial nebula. The black solid line shows P (Eq. (6)), the dashed lines show (cf. Eq. (7)). Different symbols represent different ionization parameters, namely open diamonds correspond to log (U) = −1, stars to log (U) = −2, open squares to log (U) = −2, and open triangles to log (U) = −4. It can be seen that Lyα and 2γ luminosities scale with P at low densities and Lyα is further enhanced at higher density. Case B values have been calculated using luminosity coefficients for T_e = 30000 K and n_H = 10²   cm^-3 from Schaerer (2003). For simplicity we always compare the results to the low density case B limit.