How to interpret this scatter plot? I am simulating a population of binary stars by generating many samples of orbital parameters. I'm investigating the relationship between the inclination of the orbit and the fraction of the acceleration* which is along the line of sight to the orbit. I produced this plot:

To me, it seems clear that there is some relationship between these quantities: the higher the inclination, the higher the y-value below which most of the points for that inclination are concentrated. I can clearly see a line on the border between the low and high density of points. It looks like a linear relationship that got "filled in" below the line, and above it, we have a few random points. However, this is a really unconcise way to describe it and doesn't help me understand the relationship between the parameters.
Is there a name, description, or mathematical statement of this type of relationship that would be helpful? Or am I just wishing for a pattern where there isn't one?
*change in velocity over a certain time interval

I don't know of a word for this kind of scatterplot. Yet, if you are trying to understand the relationship between the two, this post might be helpful.
Two other thoughts to help identify a relationship in a visual way.

*

*Add a loess line or spline.

*Consider whether there are groups in your data that might be meaningful to color separately and/or create a loess line/spline for each one. Seeing this, part of me wonders whether there is some group (or groups) that is bounded for some reason and another that is not.

