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Eggemeier, Benedikt; Redondo, Javier; Dolag, Klaus; Niemeyer, Jens C.; Vaquero, Alejandro (2020): First Simulations of Axion Minicluster Halos. In: Physical Review Letters, Vol. 125, No. 4, 041301
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We study the gravitational collapse of axion dark matter fluctuations in the postinflationary scenario, so-called axion miniclusters, with N-body simulations. Largely confirming theoretical expectations, overdensities begin to collapse in the radiation-dominated epoch and form an early distribution of miniclusters with masses up to 10(-12) M-circle dot. After matter-radiation equality, ongoing mergers give rise to a steep power-law distribution of minicluster halo masses. The density profiles of well-resolved halos are Navarro-Frenk-White-like to good approximation. The fraction of axion dark matter in these bound structures is similar to 0.75 at redshift z = 100.