Quasars and their host galaxies in the first Gyr of the Universe

Quasars are the brightest (non-transient) objects observed at the highest
redshifts, z>7. Such high redshift quasars are important for several
reasons. Firstly, detailed analysis of quasar spectra provide unique
information about the baryonic and physical condition of the Universe
during the epoch of reionisation. Furthermore, the density of high
redshift quasars puts powerful constraints on the mechanisms that are
required to seed and grow >10^9 Msun supermassive black holes less than a
Gyr after the Big Bang. Lastly, as these massive black holes are thought
to be located in the progenitors of the massive early type galaxies we see
in the local Universe, studying the host galaxies of the most distant
quasars enables us to probe the formation of massive galaxies in the early
Universe.

Because high redshift quasars are rare, multi-band surveys covering large
areas on the sky are required to discover such objects. In this talk I
will describe our successful programme aimed at discovering quasars at the
highest redshifts in various optical and near-infrared surveys, such as
Pan-STARRS1, UKIDSS and VIKING. I will highlight the results of our
search, which includes the discovery of more than 100 new quasars in the
first Gyr of the Universe. I will describe our on-going multi-wavelength
follow-up observations to characterise the distant quasars, their power
source and their environment, in particular our ALMA programmes to study
the galaxies hosting these luminous objects. I will present the results of
these observations, and discuss the implications for massive galaxy and
black hole formation at high redshift and our understanding of the
relation between the black hole mass and the bulge mass of galaxies.