Polarization efficiency and dust phase

We correlated the degree of interstellar polarization P and polarization efficiency (the ratio of P to the colour excess E(B-V) or extinction AV) with dust phase abundances. We detect an anticorrelation between P and the dust phase abundance of iron in non silicate-containing grains [Fe(rest)/H]_d_, a correlation between P and the abundance of Si, and no correlation between P/E(B-V) or P/AV and dust phase abundances.

These findings can be explained if mainly the silicate grains aligned by the radiative mechanism are responsible for the observed interstellar linear polarization.