Systematic variations of interstellar linear polarization and growth of dust grains

TL;DR

This study interprets the relationship between interstellar polarization parameters and dust grain growth, suggesting coagulation as the main growth mechanism based on observational data and dust grain modeling.

Contribution

It provides a quantitative interpretation of polarization curve parameters and links their variations to dust grain growth mechanisms, especially coagulation, using observational data and spheroidal grain models.

Findings

The relation $K \\approx 1.7 \\lambda_{max}$ is linked to dust grain coagulation.

Dust grain size correlates with polarization parameters.

Coagulation, not mantle accretion, explains the observed polarization trends.

Abstract

A quantitative interpretation of the observed relation between the interstellar linear polarization curve parameters $K$ and $\lambda_{\max}$ characterizing the width and the wavelength of a polarization maximum, respectively, is given. The observational data available for 57 stars located in the dark clouds in Taurus, Chamaeleon, around the stars $\rho$ Oph and R CrA are considered. The spheroidal particle model of interstellar dust grains earlier applied to simultaneously interpret the interstellar extinction and polarization curves in a wide spectral range is utilized. The observed trend $K \approx 1.7 \lambda_{\max}$ is shown to be most likely related to a growth of dust grains due to coagulation rather than mantle accretion. The relation of the parameters $K$ and $\lambda_{\max}$ with an average size of silicate dust grains is discussed.