Does it make sense to visualize dark matter as roughly spherical, or oblate, around a spiral galaxy? Perhaps incorrectly, I picture dark matter as analogous to a planet, or star, with the visible disk of the galaxy forming the equatorial plane. Is this reasonable picture of what we observe through lensing, and accounting for the constant rate of rotation? If so, is there thought to be a radial density gradient in the dark matter, something akin to the mostly linear density gradient of earth's atmosphere, or is the dark matter thought to be more of a constant density? Also, does the dark matter rotate with the galaxy? If the planet analogy is reasonable, insomuch as the dark matter has an axis of rotation, what's the force is that keeps what I'll assume to be 'particles' of dark matter near the poles from simply falling into the center of the galaxy? Much thanks to anyone who can set me straight, and thanks so much to everyone for making this such a valuable resource for learning about the universe!