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Paper: Spectral uncertainties and the luminosity function of quasars
Volume: 21, The Space Distribution of Quasars
Page: 180
Authors: Giallongo, Emanuele; Vagnetti, Fausto
Abstract: Uncertainties in the spectral index of the UV spectrum of QSOs induce systematic biases in the estimate of the cosmological evolution of the luminosity function (LF). In a framework of pure exponential luminosity evolution we obtain a slower intrinsic evolution of the LF for z less than 2.2 after correction for uncertainties in the k-correction adopted. The slower evolution helps to reduce the apparent density decline of high redshift QSOs (z greater than 2.5) observed in the red band. Indeed we find that color selected surveys are consistent with a scenario of pure luminosity evolution up to z approximately 4. The apparent decline in the redshift distribution is explained in terms of the sliding down along the steep side of the luminosity function for increasing redshift. It is suggested that quasar-to-quasar dispersion of the UV spectral index could represent average variability of individual objects.
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