Adaptive Optics Observations of 3 micron Water Ice in Silhouette Disks in the Orion Nebula Cluster and M43

TL;DR

This study uses adaptive optics to observe water ice in silhouette disks within the Orion Nebula, confirming the inclination angle for ice detection and analyzing ice properties over several years.

Contribution

First near-infrared adaptive optics observations of water ice in silhouette disks in the Orion Nebula, establishing critical inclination angles and ice stability over time.

Findings

Water ice absorption detected in two disks, absent in two others.

Critical inclination angle for water ice detection is 65-75 degrees.

Crystallized water ice profile remains unchanged over 3.63 years.

Abstract

We present the near-infrared images and spectra of four silhouette disks in the Orion Nebula Cluster (ONC; M42) and M43 using the Subaru Adaptive Optics system. While d053-717 and d141-1952 show no water ice feature at 3.1 micron, a moderately deep (tau~0.7) water ice absorption is detected toward d132-1832 and d216-0939. Taking into account the water ice so far detected in the silhouette disks, the critical inclination angle to produce a water ice absorption feature is confirmed to be 65-75deg. As for d216-0939, the crystallized water ice profile is exactly the same as in the previous observations taken 3.63 years ago. If the water ice material is located at 30AU, then the observations suggest it is uniform at a scale of about 3.5AU.