I'm not yanking your chain. Check out these images.
The following two images postulate an extended galactic disk made of dark matter causing the angular velocity of orbiting stars to remain higher than expected at greater distance from the galactic center.

This is a photo of the Sombrero galaxy as we usually see it with lots of other galaxies visible in the background. The next photo is zoomed out and overexposed. We see that a huge dark halo appears around it, as postulated.

