That’s certainly a useless chart. There are no units on the vertical axis, and not even an axis on the horizontal. It looks to me like a fisherman who laid his fish hooks out on a black mat.
One might assume the vertical units are solar mass, that the scale is logarithmic. and that the x axis is simply an arbitrary place to put the fish hooks, but what do the vertical separation, horizontal separation, and the three ball hooks signify?
You covered my issues with it. The text spends almost no time describing what the graphic means.
1. Yes, there are units on the vertical axis
2. There is no horizontal axis
Q: why no mergers over 80 solar masses detected?
- presumably the detection drops off as the masses get smaller. But why no larger mergers!