Slowly rotating Bose-Einstein condensate compared with the rotation curves of 12 dwarf galaxies

Kun, Emma and Keresztes, Zoltán and Gergely, Árpád László (2020) Slowly rotating Bose-Einstein condensate compared with the rotation curves of 12 dwarf galaxies. ASTRONOMY & ASTROPHYSICS, 633. ISSN 0004-6361

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Abstract

Context. The high plateaus of the rotation curves of spiral galaxies suggest either that there is a dark component or that the Newtonian gravity requires modifications on galactic scales to explain the observations. We assemble a database of 12 dwarf galaxies, for which optical (R-band) and near-infrared (3.6 μm) surface brightness density together with spectroscopic rotation curve data are available, in order to test the slowly rotating Bose-Einstein condensate (BEC) dark matter model. Aims: We aim to establish the angular velocity range compatible with observations, bounded from above by the requirement of finite-size halos, to check the model fits with the dataset, and the universality of the BEC halo parameter ℛ. Methods: We constructed the spatial luminosity density of the stellar component of the dwarf galaxies based on their 3.6 μm and R-band surface brightness profiles, assuming an axisymmetric baryonic mass distribution with arbitrary axis ratio. We built up the gaseous component of the mass by employing an inside-truncated disk model. We fitted a baryonic plus dark matter combined model, parametrized by the M/L ratios of the baryonic components and parameters of the slowly rotating BEC (the central density ρc, size of the BEC halo ℛ in the static limit, angular velocity ω) to the rotation curve data. Results: The 3.6 μm surface brightness of six galaxies indicates the presence of a bulge and a disk component. The shape of the 3.6 μm and R-band spatial mass density profiles being similar is consistent with the stellar mass of the galaxies emerging wavelength-independent. The slowly rotating BEC model fits the rotation curve of 11 galaxies out of 12 within the 1σ significance level, with the average of ℛ as 7.51 kpc and standard deviation of 2.96 kpc. This represents an improvement over the static BEC model fits, also discussed. For the 11 best-fitting galaxies the angular velocities allowing for a finite-size slowly rotating BEC halo are less then 2.2 × 10-16 s-1.For a scattering length of the BEC particle of a ≈ 106 fm, as allowed by terrestrial laboratory experiments, the mass of the BEC particle is slightly better constrained than in the static case as m ∈ [1.26 × 10-17 ÷ 3.08 × 10-17] (eV c-2).

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