Slant, Fan, and Narrow: the Response of Stellar Streams to a Tilting Galactic Disk

Understand

Stellar streams are sensitive tracers of the gravitational potential, which is typically assumed to be static in the inner Galaxy.

• However, massive mergers like Gaia-Sausage-Enceladus can impart torques on the stellar disk of the Milky Way that result in the disk tilting at rates of up to 10-20 deg/Gyr.
• Here, we demonstrate the effects of disk tilting on the morphology and kinematics of stellar streams.
• Through a series of numerical experiments, we find that streams with nearby apocenters $(r_{\rm apo} \lesssim 20~\rm{kpc})$ are sensitive to disk tilting, with the primary effect being changes to the stream's on-sky track and width.