When and how do supermassive black holes form? How can we explain the existence of billion solar mass black holes observed in the center of quasars at the very beginning of our universe? The lifetime of quasars - the time that galaxies shine as luminous quasars and during which the bulk of the black hole growth occurs - is one of the most fundamental quantities for understanding black hole growth and quasar evolution. We develop new methods to constrain quasar lifetimes in the early universe by measuring for instance the sizes of their proximity zones observed in their rest-frame UV spectra, which is a region of enhanced transmitted flux around the quasar due to its own ionizing radiation. Applying this method we found a population of very young quasars, which challenges our current understanding of black hole growth. Combining different estimates of quasar lifetimes using state-of-the-art ground- and space-based observatories will allow us to understand and differentiate between different black hole formation models in the near future.
When and how do supermassive black holes form? How can we explain the existence of billion solar mass black holes observed in the center of quasars at the very beginning of our universe? The lifetime of quasars - the time that galaxies shine as luminous quasars and during which the bulk of the black hole growth occurs - is one of the most fundamental quantities for understanding black hole growth and quasar evolution. We develop new methods to constrain quasar lifetimes in the early universe by measuring for instance the sizes of their proximity zones observed in their rest-frame UV spectra, which is a region of enhanced transmitted flux around the quasar due to its own ionizing radiation. Applying this method we found a population of very young quasars, which challenges our current understanding of black hole growth. Combining different estimates of quasar lifetimes using state-of-the-art ground- and space-based observatories will allow us to understand and differentiate between different black hole formation models in the near future.