Dark matter and supermassive black holes

[Lsos]

I have a rather simple question. Dark matter was first proposed because galaxies appeared to have more mass than was observable. That's fine. But then later, supermassive black holes were discovered to be at the center of every galaxy. That's billions of solar masses more in each galaxy than was observable.

Now I kind of feel like I'm out of the loop here, but it just seems obvious that the discovery of previously unseen BILLIONS of solar masses in each galaxy would have some impact on a theory that states there is lots of unseen mass in each galaxy.

And yet I never heard anything even remotely connecting these two theories. Just seems kind of strange to me. Anybody want to shed some light on this?

 

[Wallace]

As big as the black holes at galaxy centres are, they make only a relatively minor contribution to the total mass of a galaxy. The problem that requires DM to exist (or something else possibly) cannot be solved by adding more mass to a galaxies centre. It is the outer parts where problems emerge, so the 'missing mass' has to reside there, not at the centre. Simulations of cosmic structure formation support this view, in that we find the central parts of galaxies are dominated by baryons (i.e. everything that isn't dark matter) while the outer parts have more dark matter.

 

[S.Vasojevic]

Why it is called dark matter? Does it have to be matter at all, or it can be something else that is causing such behavior of galaxies?

 

[Chalnoth]

Why it is called dark matter? Does it have to be matter at all, or it can be something else that is causing such behavior of galaxies?

Because it's matter that isn't visible. Hence dark.

And no, it can't really be something else, because it's not just galaxy behavior that dark matter explains, but a whole host of other things.

 

[Naty1]

Post #2 is an excellent summary. You can read about Vera Rubin's work for some details of the experimental findings that led to some initial understanding of dark matter halo's/spider webs in the outer reaches of galaxies.
It's actaully pretty funny that we think we are so smart but have little idea what's inside black holes and no idea what constitutes 96% (dark matter and dark energy) of our universe (on our side of horizons)...lots to do!

 

[Lsos]

Ok, I guess that all makes sense. Still...BILLIONS of solar masses. Isn't there only billions of solar masses in a galaxy?
But yeah, the part where it's only at the center makes sense. Thanks everyone.

 

[Chalnoth]

It's actaully pretty funny that we think we are so smart but have little idea what's inside black holes and no idea what constitutes 96% (dark matter and dark energy) of our universe (on our side of horizons)...lots to do!

And I find that statement to be nonsensical. Especially given the observational challenge it's been to discover these things about our universe.

 

[Chalnoth]

Ok, I guess that all makes sense. Still...BILLIONS of solar masses. Isn't there only billions of solar masses in a galaxy?
But yeah, the part where it's only at the center makes sense. Thanks everyone.

Try hundreds of billions of stars. The supermassive black holes are only a couple percent the total baryonic mass (if that).