Optical imaging polarimetry of the LkCa 15 protoplanetary disk with SPHERE ZIMPOL

TL;DR

This study uses optical imaging polarimetry with SPHERE ZIMPOL to reveal new features of the LkCa 15 protoplanetary disk, including the far side of the gap and the inner disk, providing insights into its structure and potential planet formation.

Contribution

First optical polarimetry observations of LkCa 15's disk, revealing the far side of the gap and resolving the inner disk for the first time, with a new system architecture model.

Findings

Detected the far side of the disk gap.

Resolved the inner disk out to 30 AU.

Suggested the inner disk may influence the protoplanet signal.

Abstract

We present the first optical (590--890 nm) imaging polarimetry observations of the pre-transitional protoplanetary disk around the young solar analog LkCa 15, addressing a number of open questions raised by previous studies. We detect the previously unseen far side of the disk gap, confirm the highly eccentric scattered-light gap shape that was postulated from near-infrared imaging, at odds with the symmetric gap inferred from millimeter interferometry. Furthermore, we resolve the inner disk for the first time and trace it out to 30 AU. This new source of scattered light may contribute to the near-infrared interferometric signal attributed to the protoplanet candidate LkCa 15 b, which lies embedded in the outer regions of the inner disk. Finally, we present a new model for the system architecture of LkCa 15 that ties these new findings together. These observations were taken during science verification of SPHERE ZIMPOL and demonstrate this facility's performance for faint guide stars under adverse observing conditions.