Okay, I added a particular parameter to top off the density in the center of the disk, and guess what? It reproduces the shape of the rotation curve as seen in that Wiki link. At the edge of the disk to some point close to the center, the rotation speed is almost constant. Then it begins to drop off in proportion to the distance from the center, in just the same way as the link shows. The value of the parameter apparently determines where the drop off begins, but it is also sensitive. I will keep working with it to try to determine what the value would be for our galaxy. So my question now is, should this be moved to ATM or astronomy when I am done, or should it just stay here?

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Let's put together the pieces of The Grand Puzzle . (website)

"Let's define another operator, Sz, which we won't pay any attention to."
"This transformation will automatically make zero equal zero."
"It may be true that zero equals zero -- and that is certainly an equality -- but I don't want to go into the details at this time."