Strong Gravitational Lensing by Wave Dark Matter Halos

Wave dark matter (WaveDM) has recently gained attention as a viable candidate to account for the dark matter content of the universe. In this paper we explore the extent to which, and under what conditions, dark matter halos in this model are able to reproduce strong-lensing systems. First, we explore analytically the lensing properties of the model, finding that a pure WaveDM density profile, the soliton profile, produces a weaker lensing effect than similar cored profiles. Then, we analyze models with a soliton embedded within a Navarro, Frenk, and White (NFW) profile, as has been found in numerical simulations of structure formation. We use a benchmark model with a boson mass of ma = 10−22 eV, for which we see that there is a bimodality in the contribution of the external NFW part of the profile, and some of the free parameters associated with it are not well constrained. We find that for configurations with boson masses 10−23 to 10−22 eV, a range of masses preferred by dwarf galaxy kinematics, the soliton profile alone can fit the data, but its size is incompatible with the luminous extent of the lens galaxies. Likewise, boson masses of the order of 10−21 eV, which would be consistent with Lyα constraints and consist of more compact soliton configurations, necessarily require the NFW part in order to reproduce the observed Einstein radii. We then conclude that lens systems impose a conservative lower bound ma > 10−24 eV and that the NFW envelope around the soliton must be present to satisfy the observational requirements.