We present the first measurement of the faint end of the QSO luminosity function at z = 3 .
The QSOs , which range from M _ { 1450 } = -21 to M _ { 1450 } = -27 , were discovered in 17 fields totaling 0.43 ~ { } { deg ^ { 2 } } using multicolor selection criteria ( the Lyman break technique ) and spectroscopic followup .
We find that the faint-end slope of the luminosity function is \beta _ { l } = 1.24 \pm 0.07 ( \Phi \propto L ^ { - \beta _ { l } } ) , flatter than the value of \beta _ { l } = 1.64 \pm 0.18 measured at lower redshift .
The integrated rest 1450Å UV luminosity of z = 3 QSOs is only 50 % of most previous estimates , and is only \simeq 8 % of that produced by Lyman break galaxies at the same redshifts .
Assuming that ionizing photons from faint QSOs are as successful in escaping their host galaxies as bright QSOs , we estimate the total contribution of QSOs to the ionizing flux J _ { 912 } at z \sim 3 , J _ { 912 } \simeq 2.4 \times 10 ^ { -22 } ergs s { -1 } cm ^ { -2 } Hz ^ { -1 } .
This estimate , which we regard as an upper limit , remains consistent with rough estimates of J _ { 912 } based on the Lyman \alpha forest “ proximity effect . ”