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

¹ Department of Experimental Physics, University of Szeged, Dóm tér 9, 6720 Szeged, Hungary
² Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary
e-mail: kun.emma0608@gmail.com
³ Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, 6720 Szeged, Hungary
e-mail: zkeresztes.zk@gmail.com
⁴ Institute of Physics, University of Szeged, Dóm tér 9, 6720 Szeged, Hungary
e-mail: laszlo.a.gergely@gmail.com

Received: 13 August 2019
Accepted: 7 November 2019

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 ρ_c, 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).