Dark photon stars: formation and role as dark matter substructure

Any new vector boson with non-zero mass (a `dark photon' or `Proca boson') that is present during inflation automatically produced at this time from vacuum fluctuations and can comprise all a substantial fraction of the observed dark matter density, as shown by Graham, Mardon, Rajendran. We demonstrate, utilising both analytic numerical studies, such scenario implies an extremely rich substructure arising purely interplay gravitational interactions quantum effects. Due to remarkable parametric coincidence between size primordial density perturbations scale which pressure relevant, inevitably collapses into gravitationally bound solitons, are fully coherent objects. The central densities these photon star', solitons typically factor $10^6$ larger than local background they have characteristic masses $10^{-16} M_\odot (10^{-5}{\rm eV}/m)^{3/2}$, where $m$ vector. During post soliton production comparable energy initially stored in, subsequently radiated from, long-lived quasi-normal modes. Furthermore, surrounded `fuzzy' halos in wave-like properties also enhanced relative usual virialized expectations. Lower compact halos, $\sim 10^5$ greater form much scales. argue that, minimum, likely survive day without being tidally disrupted. This substructure, we anticipate arises other mechanisms, opens up wide range direct indirect detection possibilities, discuss companion paper.