What do the yellow lashes/wings on the B737 PFD indicate? When I was looking at a YouTube clip of a B737 doing a landing, I couldn't help but notice something on the PFD:

What do these yellow lashes/wings indicate on the artificial horizon?


Image Source (Added green arrows for question clarity)

They were on for the entire approach and remained on even after touchdown.
They display the maximum pitch that can be exercised with the current configuration of the aircraft. 

Using data which is measured in modern airliners, a maximum pitch angle can be calculated and displayed to the pilot on the primary display. It is described fully on this page (h/t @mins)


  With airplane aerodynamic specific data and the angle of attack measurement, we can have an effective pitch limit indicator PLI. A pitch limit indicator informs the user about the current difference between $max(\alpha)$ and the current $\alpha$. In many commercial airplane the pitch limit indicator is integrated within the glass cockpit, as shown in Figure 3; with this setup the pilot has a real-time indication of how much can pull on the column.