Constraints on Stupendously Large Black Holes

Understand

We consider the observational constraints on stupendously large black holes (SLABs) in the mass range $M \gtrsim 10^{11}\,M_{\odot}$.

• These have attracted little attention hitherto and we are aware of no published constraints on a SLAB population in the range $(10^{12}$ - $10^{18})\,M_{\odot}$.
• However, there is already evidence for black holes of up to nearly $10^{11}\,M_{\odot}$ in galactic nuclei, so it is conceivable that SLABs exist and they may even have been seeded by primordial black holes.
• We focus on limits associated with (i) dynamical and lensing effects, (ii) the generation of background radiation through the accretion of gas during the pregalactic epoch, and (iii) the gamma-ray emission from the annihilation of the halo of weakly interacting massive particles (WIMPs) expected to form around each SLAB if these provide the dark matter.