Searching for correlations in GAIA DR2 unbound star trajectories

Understand

Scattering events with compact objects are expected in the primordial black hole (PBH) cold dark matter (CDM) scenario due to close encounters between stars and PBH in the dense environments of dwarf spheroidals.

• We develop a Bayesian framework to search for correlations among Milky Way stellar trajectories and those of globular clusters and dwarf galaxies in the halo, and other nearby galaxies.
• We apply the method to a selection of hypervelocity stars (HVS) and globular clusters from Gaia DR2 catalog, and known nearby (mostly dwarf) galaxies with full phase-space and size measurements.
• We report positive evidence for trajectory intersection $\sim$20-40 Myr ago of up to 2 stars, depending on priors, with the Sagittarius dwarf Spheroidal (dSph) galaxy when assuming Marchetti et al.