Abstract

Quasars are the brightest, non-transient objects observed at the highest redshifts, z>7, which makes them unique probes of the evolution of black holes, massive galaxies and the intergalactic medium: the density of high redshift quasars puts powerful constraints on the mechanisms that are required to seed and grow supermassive, >10^9 solar mass black holes less than a Gyr after the Big Bang. Detailed analysis of quasar spectra at observed optical and near-infrared wavelengths provide unique information about the baryonic and physical condition of the universe during the epoch of reionisation. And observations in the (sub)millimeter can constrain the gas and dust content, star formation rate and masses of the galaxies hosting these luminous quasars. In this talk I will review the recent progress in locating luminous quasars in the early universe using very wide field optical and near-infrared surveys. I will present the results of various multi-wavelength follow-up programmes, focussing on our recent ALMA observations of the quasar host galaxies and discuss the implications of the findings on massive galaxy formation and cosmic reionisation.