If there was a single object at the center of the galaxy, then the notorious 'problem of rotation curves of galaxies'
would not actually be a problem. AKA Rubin's problem is solved by realizing that spiral galaxies are binary
systems with two super-massive objects emitting stars - that is why there are typically two arms to such galaxies.
Because they emit stars (mass) they can only be called 'white-holes' (apologies if that term is used elsewhere).
The following graph was generated in computer algorithm, and it clearly shows the gravitational structure
of a spiral galaxy by the emission of stars from each of the pair.
More of this is explored at this link:
Summary of Rotation Curves of Galaxies
You may also want to google "Rubin's problem" if you are unfamiliar with it.
"Rubin's problem" is not a problem with Black Holes which have been independently verified.. It is well understood that spiral galaxies can have two centers.
Where does Vera Rubin propose that Black Holes do not exist based on her work?
Black Holes described based on Vera Rubin;s work:
How Black Holes create the Gravitational Anomaly “Dark Matter” has been inferred from