Contributed Talk - Splinter SMBHs
Wednesday, 23 September 2020, 14:55 (virtual room K)
The Formation and Growth of Supermassive Black Holes at Early Cosmic Epochs
Observations of high-redshift quasars show that they host supermassive black holes (SMBHs) already less than ~1 Gyr after the Big Bang. It has been argued that in order to rapidly grow these SMBHs in such short amounts of cosmic time, they need to accrete matter over timescales comparable to the age of the universe, and thus the lifetime of quasars - the integrated time that galaxies shine as active quasars - is expected to be of order ~10^9 yr at z~6, even if they accrete continuously at the Eddington limit. I will present a new method to obtain model-independent constraints on the lifetime of high-redshift quasars with unprecedented precision, based on measurements of the sizes of ionized regions around quasars, known as proximity zones. The sizes of these proximity zones are sensitive to the lifetime of the quasars, because the intergalactic gas has a finite response time to the quasars’ radiation. Applying this method to quasar spectra at z>6, we discover an unexpected population of very young quasars, indicating lifetimes of only ~10,000 years, which poses significant challenges on current black hole formation models. I will show results from our on-going multi-wavelength survey to detect and characterize young quasars and their environments. Furthermore, I will discuss several modifications to the current SMBH formation paradigm that might explain our results, e.g. super-critical mass accretion rates, massive initial black hole seeds in excess of stellar remnants, or highly obscured quasar growth phases. In the end I will show how we aim to disentangle the various scenarios by means of on-going and future IFU observations with MUSE and the James Webb Space Telescope, in order to shed new light onto the formation and growth of the first SMBHs in the universe.