Gaps and length asymmetry in the stellar stream Palomar 5 as effects of Galactic bar rotation

Understand

Recent Pan-STARRS data show that the leading arm from the globular cluster Palomar 5 (Pal 5) appears shorter than the trailing arm, while simulations of Pal 5 predict similar angular extents.

• We demonstrate that including the spinning Galactic bar with appropriate pattern speeds in the dynamical modeling of Pal 5 can reproduce the Pan-STARRS data.
• As the bar sweeps by, some stream stars experience a difference in net torques near pericenter.
• This leads to the formation of apparent gaps along Pal 5's tidal streams and these gaps grow due to an energy offset from the rest of the stream members.