Dark Matter Halo: Modeling Rotational Effect on Galaxy V(r)

[Creebe]

Hello,

I'm a third year engineering physics student, and my team and I are trying to model how the rotation (V(r)) of a galaxy is affected by the possible existence of the dark matter halo. Here are my questions:

Regarding the dark matter halo:

The integral of the mass density function is divergent at 0, how do we deal with it? How does it make any physical sense.
Here's the formula:
http://en.wikipedia.org/wiki/Navarro-Frenk-White_profile

Is the Milky Way Galaxy dark matter-dominant?

 

[IsometricPion]

The integral of the mass density function is divergent at 0, how do we deal with it? How does it make any physical sense.

While the density diverges at 0 radius, the integral of the density (which gives the mass within a given radius) does not (it goes to zero as one might expect).

Is the Milky Way Galaxy dark matter-dominant?

The wikipedia page you listed links to a http://iopscience.iop.org/0004-637X/573/2/597/pdf/0004-637X_573_2_597.pdf" that indicates (pg. 604, tables 1 and 2) that the ratio of the mass of dark matter to the mass of the disk and bulge of the galaxy within 3 kpc of the center is 0.95 according to the "favored" model without exchange of angular momentum (between normal matter and dark matter) and 0.24 according to the "favored" model with angular momentum exchange. So, while a significant percentage of the matter within that radius is dark matter, normal matter constitutes the majority of the matter (especially in the latter model, which I would think would be more realistic).

 

[zhermes]

Is the Milky Way Galaxy dark matter-dominant?

Overall: yes. If you look at the entire milky-way galaxy, DM has >5 times as much mass. Baryonic matter, however, is dominant within about the half-light radius (something like 100 kpc)

 

[harcel]

Allthough I agree that in the inner parts the Milky Way is baryon dominated. Nevertheless, the half light radius of the Milky Way is not even close to 100 kpc (that is almost the virial radius of ots host dark matter halo), but rather of the order of a few kpc.

 

[zhermes]

Allthough I agree that in the inner parts the Milky Way is baryon dominated. Nevertheless, the half light radius of the Milky Way is not even close to 100 kpc (that is almost the virial radius of ots host dark matter halo), but rather of the order of a few kpc.

Sorry, yes---more like a few kpc---for sure!