Interstellar polarization and grain alignment: the role of iron and silicon^⋆

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: voshchinnikov@mpia.de
² Sobolev Astronomical Institute, St. Petersburg University, Universitetskii prosp. 28, 198504 St. Petersburg, Russia
e-mail: nvv@astro.spbu.ru
³ Isaac Newton Institute of Chile, St. Petersburg Branch, Russia
⁴ IUCAA, Post Bag 4, Ganeshkhind, 411 007 Pune, India

Received: 25 July 2011
Accepted: 9 March 2012

Abstract

We compiled the polarimetric data for a sample of lines of sight with known abundances of Mg, Si, and Fe. We correlated the degree of interstellar polarization P and polarization efficiency (the ratio of P to the colour excess E(B − V) or extinction A_V) 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/A_V 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.