Dependence of equivalent width of quasar emission lines on UV-optical spectral index

Using 192 composite spectra stacked from subsamples of individual SDSS quasar spectra binned in spectral index, α_λ, and logarithm of monochromatic luminosity at 1450 Å, log l ₁₄₅₀, and modelling separate spectral ranges with superposition of emission lines it was found that: there is a dependence of emission line equivalent width (EW) on α_λ (correlation or anti-correlation) for some lines, mostly for those lines for which the Baldwin effect is detected, while for the lines for which the Baldwin effect is not observed any α_λ-dependence was found.