BEC vortices as an observational signature of ultra-light bosonic dark matter

Abstract: Ultra-light bosonic dark matter (ULDM) is an interesting and promising dark matter candidate. While the wave-like nature of ULDM has been widely studied in the literature, we explore another distinctive feature of ULDM as Bose-Einstein Condensate (BEC) in this paper: the emergence of vortices in a rotating BEC-ULDM halos. Using numerical solution of the GPP equation, we demonstrate that a lattice of vortices ,underdensity columns that carry angular momentum, naturally forms in a ULDM halo under conditions similar to those of the Milky Way. Furthermore, we study the gravitational lensing by these vortices as a possible observational signature of BEC-ULDM. If the vortices are large enough and the halo's rotational axis align with the line of sight, regularly separated brightness anomalies can be produced, providing strong evidence for BEC-ULDM.