Gregory's ServerOkay, so what does that mean about the black hole mass distribution? Well, let's apply that scaling relation from toot #2. In the figure we find that there are about **twice** as many very massive black holes than suggested from previous models (which we might expect given that there are more big galaxies than prior models!). Our model (and its uncertainty) is shown with the violet band.
The number of black holes above 10 billion times the mass of our sun predicted by our model actually pretty closely matches what folks have found (the grey histogram)!
6/8
Now things get spicy. Over the past couple years, folks have measured the **cosmic gravitational wave background**, a low background hum in spacetime itself coming from all directions. This hum is thought to be due to the mergers of supermassive black holes across the universe, which each ring out with their own characteristic amplitude and frequency. Those billions of mergers add incoherently and produce something that sounds like static on Earth.
The amplitude of that static is a **huge** open question -- last year there were a number of groups which measured something that looked a lot like that static, with a characteristic strain amplitude of 2.4 parts in 1000000000000000.
If this signal is due to supermassive black holes, what does our new model say about it? Well, with some reasonable assumptions you can compute it! And we find their number!
In the figure we see our measured strain along with several other prior measurements.
7/8
Now things get spicy. Over the past couple years, folks have measured the **cosmic gravitational wave background**, a low background hum in spacetime itself coming from all directions. This hum is thought to be due to the mergers of supermassive black holes across the universe, which each ring out with their own characteristic amplitude and frequency. Those billions of mergers add incoherently and produce something that sounds like static on Earth.