Constraining the Gravitational Potential from the Projected Morphology of Extragalactic Tidal Streams

Understand

The positions and velocities of stellar streams have been used to constrain the mass and shape of the Milky Way's dark matter halo.

• Several extragalactic streams have already been detected, though it has remained unclear what can be inferred about the gravitational potential from only 2D photometric data of a stream.
• We present a fast method to infer halo shapes from the curvature of 2D projected stream tracks.
• We show that the stream curvature vector must point within 90 deg of the projected acceleration vector, in the absence of recent time-dependent perturbations.