The protoplanetary system HD 100546 in H α polarized light from SPHERE/ZIMPOL: A bar-like structure across the disk gap?

Context. HD 100546 is one of the few known pre-main-sequence stars that may host a planetary system in its disk. Aims. This work aims to contribute to our understanding of HD 100546 by analyzing new polarimetric images with high spatial resolution. Methods. Using VLT/SPHERE/ZIMPOL with two filters in Hα and the adjacent continuum, we have probed the disk gap and the surface layers of the outer disk, covering a region 3σ) of a ~20 au bar-like structure that crosses the gap through the central region of HD 100546. Conclusions. In the absence of additional data, it is tentatively suggested that the bar could be dust dragged by infalling gas that radially flows from the outer disk to the inner region. This could represent an exceptional case in which a small-scale radial inflow is observed in a single system. If this scenario is confirmed, it could explain the presence of atomic gas in the inner disk that would otherwise accrete on to the central star on a timescale of a few months/years, as previously indicated from spectro-interferometric data, and could be related with additional (undetected) planets.