Very Large Halo Around the Andromeda Galaxy

[Tanelorn]

Using the Hubble Space Telescope, astronomers have discovered that the immense halo of gas enveloping the Andromeda galaxy is about six times larger and 1,000 times more massive than previously thought.

http://scitechdaily.com/halo-around-the-andromeda-galaxy-is-larger-than-previously-thought/

Would this massive, atmosphere like halo help explain galaxy rotations curves and the need for dark matter?

 

[Chalnoth]

No, because this halo has little to no impact on the gravitational forces for stars within a few tens of kiloparsecs of the center of the galaxy, which is where rotation curves are measured.

 

[Tanelorn]

ok thanks Chalnoth, I initially thought that being 1,000 times more massive might change the orbital speeds in some way, but as you say it is very diffuse.

 

[Chalnoth]

Yup. As much of this stuff as there is, there's still at least ten times as much dark matter (with a similar distribution).