Water Ice in the Edge-On Orion Silhouette Disk 114--426 from JWST NIRCam Images

TL;DR

This study uses JWST/NIRCam images to detect water ice in the edge-on protoplanetary disk 114--426, revealing its composition, structure, and potential hydrogen excitation, advancing understanding of planet-forming environments.

Contribution

First detection of water ice in the silhouette of an edge-on protoplanetary disk using JWST, with detailed analysis of ice abundance, grain sizes, and disk morphology.

Findings

Water ice detected at 3 microns in the disk.

Ice-to-refractory mass ratio up to 0.2.

Evidence of a tilted inner disk from brightness asymmetry.

Abstract

We examine images of the protoplanetary disk 114--426 with JWST/NIRCam in 12 bands. This large disk is oriented edge-on with a dark midplane flanked by lobes of scattered light. The outer edges of the midplane are seen in silhouette against the Orion Nebula, providing a unique opportunity to study planet-forming material in absorption. We discover a dip in the scattered light of the disk at 3\,$\micron$ -- compelling evidence for the presence of water ice. The 3\,$\micron$ dip is also seen in the silhouette of the disk, where we quantify the ice abundance with models of pure absorption and avoid the complications of disk scattering effects. We find grain ice-to-refractory mass ratios of up to $\sim$0.2, maximum grain sizes of 0.25 to 5\,$\micron$, and a total dust plus ice mass of 0.46\,$M_\oplus$ in the silhouette region. We also discover excess absorption in the NIRCam bands that include the Paschen $\alpha$ line, suggesting there may be excited atomic hydrogen in the disk. Examining the morphology of the scattered light lobes reveals that they are laterally offset from each other and exhibit a brightness asymmetry that flips with wavelength -- both evidence for a tilted inner disk in this system.