A Dipole on the Sky: Predictions for Hypervelocity Stars from the Large Magellanic Cloud

TL;DR

This paper predicts the sky distribution of hypervelocity stars ejected from the Large Magellanic Cloud, highlighting a dipole pattern influenced by the LMC's motion and suggesting Gaia will detect many such stars in the southern sky.

Contribution

It introduces a model for hypervelocity stars ejected from the LMC, emphasizing the dipole distribution caused by the LMC's orbital velocity, distinct from Galactic Center ejections.

Findings

Dipole density distribution of HVSs aligned with LMC motion

A tendril of HVSs leading the LMC matches observed clustering

Gaia expected to detect many LMC-origin HVSs in the southern hemisphere

Abstract

We predict the distribution of hypervelocity stars (HVSs) ejected from the Large Magellanic Cloud (LMC), under the assumption that the dwarf galaxy hosts a central massive black hole (MBH). For the majority of stars ejected from the LMC the orbital velocity of the LMC has contributed a significant fraction of their galactic rest frame velocity, leading to a dipole density distribution on the sky. We quantify the dipole using spherical harmonic analysis and contrast with the monopole expected for HVSs ejected from the Galactic Center. There is a tendril in the density distribution that leads the LMC which is coincident with the well-known and unexplained clustering of HVSs in the constellations of Leo and Sextans. Our model is falsifiable, since it predicts that Gaia will reveal a large density of HVSs in the southern hemisphere.