Abstract

Quasars are widely used in astrophysics to probe various environments, ranging from large-scale studies of clustering and the intergalactic medium to galactic-scale studies of the interstellar and circumgalactic media. Moreover, quasars are intriguing objects on their own and many aspects of quasar evolution and the multitude of observational phenomena are still not fully understood. One main limitation to quasar studies in general is the pre-selection for spectroscopic observations. The largest spectroscopic quasar samples to date have been selected based primarily on optical colors with inhomogeneous inclusion of multi-wavelength data to increase purity. Such identifications may lead to potential biases in the derived quasar demographic and can have severe consequences for foreground absorption studies. Various other methods for selecting quasars based on different parts of the quasar energy distribution have been employed (e.g., radio, X-ray or IR), yet current samples are much smaller than optically-selected samples. In this talk, I will highlight our efforts to obtain the first color-independent quasar sample by selecting candidate quasars purely based on astrometry from Gaia. This method allows us to select a sample of optically bright quasars with no further assumptions on the spectral shape. The talk will focus on the implications for studies of foreground absorption systems as well as the quasar demographic in general.