Description
The majority of observations of Lyα forest in the vicinity of quasars suggest that these quasars have optically/UV bright lifetimes of t_Q~10^5-10^7yr. However, in some cases t_Q≤10^4yr is implied. Such short lifetimes pose a challenge for the growth of supermassive black holes at z≥6. One possibility to alleviate this issue is if the quasars accrete material in episodes and hence their luminosity varies over time. Unfortunately, it is difficult to distinguish between very young quasars and old quasars which experienced episodic accretion using only the Lyα forest observations. In this talk I will present models of 21-cm forest absorption in the proximity of z≥6 radio-loud quasars. I will show that the extent of the proximate 21-cm forest absorption is sensitive to the integrated lifetime of the quasar rather than the time of the last accretion episode only (as is the case for the Lyα forest), and hence its observations would provide complementary constraints on the models of supermassive black hole growth.
