Milky Way Kinematics: Measurements at the Subcentral Point of the Fourth Quadrant

Understand

We use atomic hydrogen (HI) data from the Southern Galactic Plane Survey to study the kinematics of the fourth quadrant of the Milky Way.

• By measuring the terminal velocity as a function of longitude throughout the fourth Galactic quadrant we have derived the most densely sampled rotation curve available for the Milky Way between 3 < R < 8 kpc.
• We determine a new joint rotation curve fit for the first and fourth quadrants, which can be used for kinematic distances interior to the Solar circle.
• From our data we place new limits on the peak to peak variation of streaming motions in the fourth quadrant to be ~10 km/s.