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Galactic KinematicsThe Local Standard of Rest (LSR)
Solar motiondisk velocity dispersion
Galactic Rotation
LSR - local standard of rest
More generally, if the Galactic potential is not axis-symmetric(e.g., because of the Galactic bar), then the LSR orbit is oval.
Solar motion: sun moving “upwards” at7 km/s wrt other stars
The residual solar motion wrt the average of local stars is
U! = −10 km s−1
V! = 5 km s−1
Currently we are near the mid-plane
Some say V = 15 km/s!
W! = 7 km s−1
σz =√∑
W 2i
Oort limit - imagine the disk as a plane parallel slab
Are we happywith these sums?
How might we get R0?
termina
l velo
city c
urve
terminal velocity curve
bumps & wiggles in rotation curves
terminal v
elocity
curve
stars
stars
gas
gas
Renzo’s rule: When you see a feature in the light,you see a corresponding feature in the rotation curve.
Fitting the bumps & wiggles at small radiisuccessful in predicting the rotation curve
at large radii.
BHB stars from SDSS
gas
stars
dark matter