The Effects of Self-Shadowing by a Puffed up Inner Rim in Scattered Light Images of Protoplanetary Disks

TL;DR

This study investigates how self-shadowing from puffed up inner rims in protoplanetary disks affects observable scattered light features, finding that smooth transitions do not produce sharp features, but sharp edges can create distinct brightness profiles.

Contribution

The paper demonstrates that puffed up inner rims with smooth transitions do not generate sharp disk features, but sharp-edged rims can produce observable broken power law brightness profiles.

Findings

Smooth transitions in puffed up rims do not create sharp features.

Sharp-edged rims can produce broken power law brightness profiles.

Observed profiles like in TW Hydrae may be explained by sharp-edged rims.

Abstract

We explore whether protoplanetary disks with self-shadowing from puffed up inner rims exhibit observable features in scattered light images. We use both self-consistent hydrostatic equilibrium calculations and parameterized models to produce the vertically puffed up inner rims. We find that, in general, the transition between the shadowed and flared regions occurs in a smooth manner over a broad radius range, and no sudden jump exists at the outer edge of the shadow in either the disk temperature or density structures. As a result, a puffed up rim cannot create sharp ring/arc/spiral-arm-like features in the outer disk as have been detected in recent direct NIR imaging of disks. On the other hand, if the puffed up rim has a sharp edge in the vertical direction, the shadowing effect can produce a distinct 3-stage broken power law in the radial intensity profile of the scattered light, with 2 steep surface brightness radial profiles in the inner and outer disk joined by a shallow transition region around the shadow edge. These types of scattered light profiles may have already been observed, such as in the recent Subaru direct imaging of the TW Hydrae system.