Systematic variations of interstellar linear polarization and growth of dust grains

The observed relation between the interstellar linear polarization curve parameters K and lambda (max) characterizing the width and the wavelength of the polarization maximum, respectively, is interpreted quantitatively. We have considered 57 stars located in four dark clouds with evidence of star formation: in Taurus, Chamaeleon, around the stars rho Oph and R CrA. In our modeling we have used the spheroidal dust grain model applied previously to simultaneously interpret the interstellar extinction and polarization curves in a wide wavelength range. The observed trend K a parts per thousand 1.7 lambda (max) is shown to be most likely related to the growth of dust grains due to coagulation rather than accretion. The relationship of the interstellar polarization curve parameters K and lambda (max) to the mean dust grain size is discussed.