The evolution of optically selected QSOs
Year: 1987
Type: article
Abstract: We report here on a determination of the QSO luminosity function (LF) and its evolution with redshift based on a new catalogue of faint ( B <20.9 mag) ultraviolet excess (UVX) QSOs with complete spectroscopic identification for almost 200 QSOs (Boyle et al. in preparation, hereafter BFSP). We find that the steep slope $(d\\,\\text{log}\\,N/dB\\simeq 0.86)$ exhibited by the number-magnitude relation for UVX QSOs flattens significantly $(d\\,\\text{log}\\,N/dB\\simeq 0.32)$ beyond B = 19.5 mag, with a UVX QSO surface density at B <20.9 mag of 36±4 per square degree. We demonstrate that this flattening corresponds to a feature in the QSO luminosity function at faint absolute magnitudes. By determining the redshift dependence of this feature we find that the evolution of QSOs at z <2.2 is most simply parameterized by a uniform increase in their luminosity with increasing redshift [ $L\\propto (1+z)^{k},\\,k=3.5\\pm 0.3\\,\\text{for}\\,\\text{a}\\,{q}_{0}=0.5$ universe). Such evolution is found to be consistent with a model in which QSOs are long-lived ( $\\simeq {10}^{10}\\,\\text{yr}$ ), gradually dimming in luminosity from their epoch of formation at z >2.2 to the present day.
Authors: B. J. Boyle, R. Fong, T. Shanks, B. A. Peterson
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3038222787