Exploding Satellites -- The Tidal Debris of the Ultra-Faint Dwarf Galaxy Hercules

Understand

The ultra-faint satellite galaxy Hercules has a strongly elongated and irregular morphology with detections of tidal features up to 1.3 deg (3 kpc) from its center.

• This suggests that Hercules may be dissolving under the Milky Way's gravitational influence, and hence could be a tidal stream in formation rather than a bound, dark-matter dominated satellite.
• Using Bayesian inference in combination with N-body simulations, we show that Hercules has to be on a very eccentric orbit (epsilon~0.95) within the Milky Way in this scenario.
• On such an orbit, Hercules "explodes" as a consequence of the last tidal shock at pericenter 0.5 Gyr ago.