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We study the formation and the subsequent mass growth of axion stars inside axion miniclusters. Numerically solving the Schrödinger-Poisson equations with realistic initial conditions we find that the axion stars exhibit similar properties to solitonic cores in ultralight bosonic dark matter halos in terms of their radial density profiles and large-amplitude oscillations. A merger of two axion stars confirms a previously found empirical law for the mass of the merged axion star. Monitoring the axion star masses over time, we observe a mass growth consistent with the mass increase of Bose stars in the kinetic regime reported by Levkov et al., confirming that the mass evolution of axion stars can be understood in terms of wave condensation. Based on this result, we predict a saturation of mass growth in relation to the minicluster mass consistent with the core-halo mass relation previously found for ultralight bosonic dark matter halos. [ABSTRACT FROM AUTHOR]

We simulate the formation and evolution of ultralight bosonic dark matter halos from cosmological initial conditions. Using zoom-in techniques, we are able to resolve the detailed interior structure of the halos. We observe the formation of solitonic cores and confirm the core-halo mass relation previously found by Schive et al. The cores exhibit strong quasinormal oscillations that remain largely undamped on evolutionary time scales. On the other hand, no conclusive growth of the core mass by condensation or relaxation can be detected. In the incoherent halo surrounding the cores, the scalar field density profiles and velocity distributions show no significant deviation from collisionless N-body simulations on scales larger than the coherence length. Our results are consistent with the core properties being determined mainly by the coherence length at the time of virialization, whereas the Schrödinger-Vlasov correspondence explains the halo properties when averaged on scales greater than the coherence length. [ABSTRACT FROM AUTHOR]

Using three-dimensional simulations, we study the dynamics and final structure of merging solitonic cores predicted to form in ultralight axion dark matter halos. The classical, Newtonian equations of motion of a self-gravitating scalar field are described by the Schrödinger-Poisson equations. We investigate mergers of ground state (boson star) configurations with varying mass ratios, relative phases, orbital angular momenta and initial separation with the primary goal to understand the mass loss of the emerging core by gravitational cooling. Previous results showing that the final density profiles have solitonic cores and Navarro-Frenk-White-like tails are confirmed. In binary mergers, the final core mass does not depend on initial phase difference or angular momentum and only depends on mass ratio, total initial mass, and total energy of the system. For nonzero angular momenta, the otherwise spherical cores become rotating ellipsoids. The results for mergers of multiple cores are qualitatively identical. [ABSTRACT FROM AUTHOR]

We present zoom-in simulations of fuzzy dark matter (FDM) halos including baryons and star formation with sufficient resolution to follow the formation and evolution of central solitons. We find that their properties are determined by the local dark matter velocity dispersion in the combined dark matter-baryon gravitational potential. This motivates a simple prescription to estimate the radial density profiles of FDM cores in the presence of baryons. As cores become more massive and compact if baryons are included, galactic rotation curve measurements are likely harder to reconcile with FDM. [ABSTRACT FROM AUTHOR]

We study tidal stripping of fuzzy dark matter (FDM) subhalo cores using simulations of the Schrödinger-Poisson equations and analyze the dynamics of tidal disruption, highlighting the differences with standard cold dark matter. Mass loss outside of the tidal radius forces the core to relax into a less compact configuration, lowering the tidal radius. As the characteristic radius of a solitonic core scales inversely with its mass, tidal stripping results in a runaway effect and rapid tidal disruption of the core once its central density drops below 4.5 times the average density of the host within the orbital radius. Additionally, we find that the core is deformed into a tidally locked ellipsoid with increasing eccentricities until it is completely disrupted. Using the core mass loss rate, we compute the minimum mass of cores that can survive several orbits for different FDM particle masses and compare it with observed masses of satellite galaxies in the Milky Way. [ABSTRACT FROM AUTHOR]

In the context of structure formation with ultralight axion dark matter, we offer an alternative explanation for the mass relation of solitonic cores and their host halos observed in numerical simulations. Our argument is based entirely on the mass gain that occurs during major mergers of binary cores and largely independent of the initial core-halo mass relation assigned to hosts that have just collapsed. We find a relation between the halo mass Mh and corresponding core mass Mc, Mc ∝ M2β-1h, where(1-β) is the core mass loss fraction. Following the evolution of core masses in stochastic merger trees, we find empirical evidence for our model. Our results are useful for statistically modeling the effects of dark matter cores on the properties of galaxies and their substructures in axion dark matter cosmologies. [ABSTRACT FROM AUTHOR]

This work studies the formation and growth of boson stars and their surrounding miniclusters by gravitational condensation using nonlinear dynamical numerical methods. Fully dynamical attractive and repulsive self-interactions are also considered for the first time. In the case of pure gravity, we numerically prove that the growth of boson stars inside halos slows down and saturates as has been previously conjectured, and detail its conditions. Self-interactions are included using the Gross-Pitaevskii-Poisson equations. We find that in the case of strong attractive self-interactions the boson stars can become unstable and collapse, in agreement with previous stationary computations. At even stronger coupling, the condensate fragments. Repulsive self-interactions, as expected, promote boson star formation, and lead to solutions with larger radii. [ABSTRACT FROM AUTHOR]

The distinctive effects of fuzzy dark matter are most visible at nonlinear galactic scales. We present the first simulations of mixed fuzzy and cold dark matter, obtained with an extended version of the nyx code. Fuzzy (or ultralight or axionlike) dark matter dynamics are governed by the comoving Schrödinger-Poisson equation. This is evolved with a pseudospectral algorithm on the root grid, and with finite differencing at up to six levels of adaptive refinement. Cold dark matter is evolved with the existing N-body implementation in nyx. We present the first investigations of spherical collapse in mixed dark matter models, focusing on radial density profiles, velocity spectra, and soliton formation in collapsed halos. We find that the effective granule masses decrease in proportion to the fraction of fuzzy dark matter which quadratically suppresses soliton growth, and that a central soliton forms only if the fuzzy dark matter fraction is greater than 10%. The nyx framework supports baryonic physics and key astrophysical processes such as star formation. Consequently, axionyx will enable increasingly realistic studies of fuzzy dark matter astrophysics. [ABSTRACT FROM AUTHOR]