Slowly rotating Bose-Einstein Condensate confronted with the rotation curves of 12 dwarf galaxies

Abstract

We assemble a database of 12 dwarf galaxies, for which optical (R-band) and near-infrared ($3.6\mu m$) surface brightness density together with spectroscopic rotation curve data are available, in order to test the slowly rotating Bose-Einstein Condensate (srBEC) dark matter model. We aim to establish the angular velocity range compatible with observations, bounded from above by the requirement of finite size halos, to check the modelfits with the dataset, and the universality of the BEC halo parameter $\mathcal{R}$. We construct the spatial luminosity density of the stellar component of the dwarf galaxies based on their $3.6\mu m$ and R-band surface brightness profiles, assuming an axisymmetric baryonic mass distribution. We build up the gaseous component by employing a truncated disk model. We fit a baryonic plus dark matter combined model, parametrized by the M/L ratios of the baryonic components and parameters of the srBEC (the central density $\rho_c$, size of the static BEC halo $\mathcal{R}$, angular velocity $\omega$) to the rotation curves. The $3.6\mu m$ surface brightness of 6 galaxies indicates the presence of a bulge and a disk component. The shape of the $3.6\mu m$ and R-band spatial mass density profiles being similar is consistent with the stellar mass of the galaxies emerging wavelength-independent. The srBEC model fits the rotation curve of 11 galaxies out of 12 within $1\sigma$ significance level, with the average of $\mathcal{R}$ as 7.51 kpc and standard deviation of 2.96 kpc. This represents an improvement over the static BEC modelfit. For the well-fitting 11 galaxies the angular velocities allowing for a finite size srBEC halo are $<2.2\times 10^{-16}$ 1/s. For a scattering length of the BEC particle of $a\approx 10^6$ fm, the mass of the BEC particle is slightly better constrained than in the static case as $m\in[1.26\times10^{-17}\div3.08\times10^{-17}]$ eV/c$^2$.