I wrote many times about kinetic and potential energy. A gravity is a potential energy. Mainstream claims the gravity is a metric curvature of the space. In String Theory are looking for a graviton mediating the gravity in an empty space. This direction of the math is not effective for now.
What curves the space if there is nothing ?
According to Casimir effect we know there is a minimum energy in a space. We call it Zero Point Energy, Vacuum Energy, Space-time, Ether, and many other words. There are oscillations (Schrondiger's Zitterbewegung) inwards schrinking with a positive energy and it causes inwards warping curvature of the space.
My suggestion is that the minimum space energy is because of the gravitational field. Every massive particle oscillate and this inwards shrinking oscillations are mediated by the Zero Point Energy or Virtual Particle Field or other words.
The density of the space oscillations between two masses is greater than behond because an inverse square distance. This shrinking oscillation causes a tension we call GRAVITY.
This idea shows an another picture of the shape of the gravitational field. It suggests an additional energetic field between masses (galaxies, galaxy clusters). Such a cylindrical consolidation of the energy in a Cosmic space far away behind a galaxy halo may explain a Dark Matter effect.
It will depend on mass distribution, shape of the galaxy and angle of the rotation plane of the galaxy according to another galaxies.