Even though we have been observing beautiful relativistic jets for more than 30 years, we still do not understand how their production is coupled with the black hole spin and the different states of the accretion flow.
Powering of relativistic jets from spinning black holes
In order to make progress in these fronts, I calculated how the spin regulates the power of jets produced by black holes accreting in the ADAF state (Nemmen et al. 2007, MNRAS, 377, 1652).
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Observational constraints on black hole spin of populations of supermassive black holes
To make things worse, it is very challenging to estimate the spin of supermassive black holes (SMBHs). Knowing the spin of SMBHs is fundamental for several reasons, chief among them: it retains a memory of the SMBH growth, with different modes of accretion or mergers implying different spin distributions.
Given observational estimates of the mass accretion rate (the engine’s “fuel”) and the jet power (the “exhaust”) (Figure 2 in the paper), this model enabled us to obtain constraints on the boost given by the black hole spin (the “turbine”). I applied this method to a sample of 9 radio galaxies observed with Chandra and found that their SMBHs are rotating close to the speed of light (a/M>0.9; Figure below).
How efficient is jet production from black holes?
Future: numerical simulations of accretion onto black holes