Unformatted text preview: distance from the Galactic center, varied with height above the Galactic plane as n ( z ) = n e-z/z h where z h = 285 pc. Also suppose that the velocity dispersion of these dwarfs varies with z as σ 2 z = σ 2 z (1 + z/z h ) , σ z = 14 km s-1 . Show that the surface mass density within 1 kpc of the plane is Σ( < 1 kpc) ’ 90 M ² pc-2 . What factor is this larger than the surface mass density in the Galactic disc at the Sun’s position? If, instead, one assumed that the velocity dispersion was inde-pendent of height above the Galactic plane, what would you ﬁnd for Σ( < 1 kpc)?...
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- Spring '11
- Galaxies, galactic center, surface mass density