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My understanding is that all Ultra Diffuse Galaxies (UDGs) have no Dark Matter nor do they have Supermassive Black Holes. It is also my understanding that all other galaxies have both Dark Matter and Supermassive Black Holes. Or am I wrong:

Is anyone able to name or site a reference to a galaxy that has Dark Matter, but has no Supermassive Black Hole at its center?

Is anyone able to name or site a reference to a galaxy with no Dark Matter, but that does have a significant Supermassive Black Hole at its center?

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  1. Ultra-Diffuse Galaxies actually have a wide range of dark matter content. Some indeed seem to have little or no dark matter, but others are quite dominated by dark matter. For example, Dragonfly 44 in the Coma Cluster has an estimated dark-matter halo mass similar to that of the Milky Way, even though the total mass of its stars is about 100 times smaller than the Milky Way's.

  2. Not all galaxies have SMBHs. M33 (aka the Triangulum Galaxy), for example, has a very small upper limit of $\sim 1500$ solar masses on any possible central black hole (Gebhardt et al. (2001)), well below the usual definition of an SMBH (i.e., $> 10^{6}$ solar masses).

  3. We currently know nothing about any possible SMBHs in UDGs. In general, these galaxies are simply too faint for any of the usual methods for measuring SMBHs to work. This is especially true given that their low stellar masses and stellar velocity dispersions imply that any central BHs that did exist and which followed the standard relations between SMBH mass and galaxy properties would have BH masses $< 10^{5}$ or $< 10^{4}$ solar masses, making them even harder to detect.

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