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The answer to this is unknown at the present time. The issue is that an accreting "seed black hole" can only accrete at a limited rate. The limitation is provided by radiation pressure from the materi …

The accretion of dark matter by a black hole is possible, but difficult. Unless its trajectory takes it into the black hole, then it will simply approach the black hole, speed up and then escape again …

Yes, it is easily possible, but it depends critically on how massive the black hole is. A simple calculation will suffice. If we take a Newtonian approximation for the tidal acceleration across a sta …

When two black holes merge, the gravitational mass of the final black hole is lower than the sum of the masses of the two merging black holes. Where has this mass gone? The answer is that it has been …

According to measurements of the cosmic microwave background the universe is geometrically flat - which means that the mass/energy density of the universe is close to the "critical value" of $\sim 10^ …

Some people certainly think that primordial black holes could account for a significant fraction of dark matter and at least provide the seeds for growing supermassive black holes in the early univers …

There is (at least for stellar mass black hole candidates). The BlackCAT catalogue, as stated in the abstract of the first reference you cite: The complete version of this catalogue will be continuou …

Gravitational waves travel at the speed of light. There are many possible sources of gravitational waves. The two confirmed detections so far (14 Sep 2016) are merging black hole binary systems, but …

The reason for the upper limit is that gravitational force scales as the product of masses over separation squared and that the closest approach of black holes is limited by their event horizons. The …

Your rough analysis is basically correct; everything may well end up in black holes eventually. But the timescale for that is very long indeed. The cross-section for direct interaction as you describe …

To a first approximation when we calculate how fast an object is orbiting around some mass distribution we can assume that the gravitational attraction it experiences is only that due to the mass inte …

The rings are not direct images of accretion disks. They are blurred images of the gravitationally lensed light from all around the black holes, with a central "shadow" due to photon orbits that fall …

If a third body interacts with a binary system then it is possible for the third body to be ejected taking away energy from the binary system. The lowering of its (negative) total energy (the sum of k …

There's a paper that gives exactly the formulae you are looking for by Sobolenko et al. (2021). They describe the merger of supermassive black holes as a three-phase process. These phases may overlap …

The jet is projected onto the image roughly in the E-W direction with the (main) jet coming towards us to the right of the black hole. The brightening in the ring is perpendicular to this. It is prob …