Herschel Observations of Protoplanetary Disks in Lynds 1641

TL;DR

This study uses Herschel observations to analyze the dust properties of 104 protoplanetary disks in Lynds 1641, revealing significant dust settling and evolution in disks at around 1.5 million years.

Contribution

First comprehensive Herschel-based analysis of protoplanetary disks in Lynds 1641, identifying new transitional disks and modeling dust settling properties.

Findings

Dust settling is significant in disks at ~1.5 Myr.

Lynds 1641 disks show signs of dust evolution similar to Taurus.

Disks in Lynds 1641 are slightly less evolved than those in Taurus.

Abstract

We analyze Herschel Space Observatory observations of 104 young stellar objects with protoplanetary disks in the ~1.5 Myr star-forming region Lynds 1641 (L1641) within the Orion A Molecular Cloud. We present spectral energy distributions from the optical to the far-infrared including new photometry from the Herschel Photodetector Array Camera and Spectrometer (PACS) at 70 microns. Our sample, taken as part of the Herschel Orion Protostar Survey, contains 24 transitional disks, eight of which we identify for the first time in this work. We analyze the full disks with irradiated accretion disk models to infer dust settling properties. Using forward modeling to reproduce the observed nKS-[70] index for the full disk sample, we find the observed disk indices are consistent with models that have depletion of dust in the upper layers of the disk relative to the mid plane, indicating significant dust settling. We perform the same analysis on full disks in Taurus with Herschel data and find that Taurus is slightly more evolved, although both samples show signs of dust settling. These results add to the growing literature that significant dust evolution can occur in disks by ~1.5 Myr.