Microlensing, flattening, ${\mathrm{\Omega }}_B$ and $h$: from assumptions, via data to tentative conclusions

Microlensing observations can be used for determining the shape of the Milky Way’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, ${\mathrm{\Omega }}_B$, 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, $h\sim 0.5$.