Captured molecules could make a Bose star visible

Abstract

A Bose star passing through cold molecular clouds may capture atoms, molecules and dust particles. The observational signature of such an event would be a relatively small amount of matter that is gravitationally bound. This binding may actually be provided by invisible dark matter forming the Bose star. We may expect a relative excess of heavier atoms, molecules, and solid dust compared to the content of giant cold molecular clouds since the velocity of heavy particles at a given temperature is lower and it may be small compared to the escape velocity, $v_{\mathrm{rms}}=\sqrt{3k_{\mathrm{B}}T/m_{\mathrm{gas}}}\ll v_{\mathrm{esc}}=\sqrt{2GM/R}$. Finally, the velocity of this captured matter cloud may correlate with the expected velocity of free dark matter particles (e.g. expected axion wind velocity relative to Earth).