Speaker
Description
The study of disc accretion physics around supermassive black hole (BH) candidates provides essential theoretical tools to test their nature. In this talk I present recent results about the accretion flow and associated emission using generalised α-discs accreting onto horizonless dark compact objects, and compare with the traditional BH scenario. The BH alternative consists in a dense and highly degenerate core made of fermionic dark matter (DM) which is surrounded by a more diluted halo able to explain the rotation curve according to the RAR model. The fact that the compactness of the dense DM core scales with particle mass, it leads to the following key findings: (i) There is always a given core compacity – corresponding particle mass – that produces a luminosity spectrum that is almost indistinguishable from that of a Schwarzschild BH of the same mass as the DM core. (ii) The disc can enter deep inside the non-rotating DM core,
allowing accretion-powered efficiencies of as high as 28%, which is comparable to that of a rotating Kerr BH. In addition, I will present new results using a key tracer of the space-time geometry of the central object: the fluorescent iron kα line and its broadening due to relativistic effects caused by the central DM core. Finally, I will show the possibility to extend this phenomenology to the full spectral energy distribution (SED) of low-mass AGN in the intriguing mass range of the central object of ~10^5-10^7 Msun.