ABSTRACT

I will present results from a survey of the most distant quasars using
data obtained with the Sloan Digital Sky Survey. These quasars are at
redshift higher than six, when the universe was only 7% of its current
age, and are among the best probes to the evolution of the early universe.
We found that these quasars are located in supermassive black holes with
mass above one billion solar masses. They are tracing the formation and
evolution of the earliest supermassive black holes and their relation
to the formation of first generation galaxies. Spectroscopy of these distant
quasars also sheds light on the distribution and status of cold, primordial
gas in the intergalactic medium. Observations show that at redshift of six,
the universe is likely going through a phase transition when hydrogen
becomes completely ionized and ended the cosmic dark ages.