Multiwavelength analysis of polarized light in HD 100453

Abstract

HD 100453 disk is a prototypical companion-disk interaction system hosting a pair of spirals and a substellar companion. We present new noncoronagraphic high-contrast imaging observations of HD 100453 with $V$ filter on SPHERE/ZIMPOL. We combined high-contrast imaging data of the reflected light from 0.55 to 2.2 $\hat{I}¼m$ using the $V$, $I^{\prime }$, $J$, and $Ks$ band data of ZIMPOL and IRDIS at VLT/SPHERE. For each observational epoch, we corrected for the smearing effect to derive the intrinsic disk-integrated polarized flux. We derived a steady increase with wavelengths from ${\hat{Q}}_{\ddot{I}}†/I_{\star }(V)=0.3\%$ to ${\hat{Q}}_{\ddot{I}}†/I_{\star }(K)=1.2\%$. We applied reference differential imaging to extract the disk intensity for the $V$ and $Ks$ bands using star hopping observations. We obtained the first $V$-band total intensity for HD 100453 with ZIMPOL star hopping. The integrated total flux $I_{\mathrm{disk}}/I_{\star }(V)=1.5\%$ increases to $I_{\mathrm{disk}}/I_{\star }(K)=4.8\%$. Both the total intensity and the polarization fraction show red colors, and the intrinsic maximum degree of polarization increases moderately from $40\%$ to $55\%$. We then used RADMC-3D radiative transfer modeling with a parametrized Henyey-Greenstein phase function to constrain the dust properties. From the $V$ to $Ks$ band, the dominating dust in the outer disk has an increasing scattering albedo and degree of polarization, while the asymmetry parameter slightly decreases. The outer disk of HD 100453 contains sub-micron-sized low porosity grains/aggregates. The cavity in scattered light is not empty and is replenished with optically thin dust with a maximum size of $\le 0.1\hat{I}¼m$. The linear polarization is higher in the spiral region than in the other regions, suggesting different dust properties in those regions.

Published in A&A, 14 pages, 10 figures, and 3 pages of Appendix