The people who made this picture have mistakenly called it dark matter, but the philosophy of space and time precludes this posibility.  For any mass to have an effect on another mass, there must exist at least one connection of gravity between the two.  Thus dark matter, would not have connections with a universe and would not "count" in the gravitation of that universe.

In the picture above, we can clearly see that the graviation represented is material that has already gone "down the drain" of the black hole.  We can tell this by the very sharp peaks.  The sharpness of the peaks indicates that these gravitational structures are very dense.  Almost every bit of the energy of these systems has already been converted from mass to gravity.  There is just enough energy left in the mass to provide identity and that is what holds the entire system together.   At some point, one of the peaks will rise so high that the energy in the mass will reach an effective value of zero and the system will come apart as another big bang.   What you are looking at in the picture is a snapshot in time before a big bang starts another universe.

Each of the peaks around the edges represent galaxies since the overall picture is of a galaxy cluster.   Thus the large peaks in the center represent the large black holes that have already gobbled entire galaxies and wil someday "eat" the remain galaxies that are already in its grasp.