NAME:
vll
PURPOSE:
return the velocity in Galactic longitude (km/s)
INPUT:
t - (optional) time at which to get vll
- obs=[X,Y,Z,vx,vy,vz] - (optional) position and velocity of observer
- (in kpc and km/s) (default=[8.5,0.,0.,0.,235.,0.]) OR Orbit object that corresponds to the orbit of the observer
ro= distance in kpc corresponding to R=1. (default: 8.5)
vo= velocity in km/s corresponding to v=1. (default: 235.)
OUTPUT:
v_l(t) in km/s
HISTORY:
2011-03-27 - Written - Bovy (NYU)
