Microlensing, flattening, $Ω_B$ and $h$: from assumptions, via data to tentative conclusions

Abstract

Microlensing observations can be used for determining the shape of the Milky Way&#39;s halo. It can be shown that the data are best described with moderately flattened halo, 0.5 < q < 0.6. We discuss, by taking into account this result, the constraints on the baryonic mass-density parameter, $Ω_B$, and their implications on the value of the Hubble constant $H_0$, i.e. $h$. Our conclusion is that current data, in order to satisfy BBNS and Galaxy dynamics constraints, strongly suggest that $h$ should take values within the lower part of the permissible range, $h\sim 0.5$.