A Flattened Protostellar Envelope in Absorption around L1157

TL;DR

This paper reports the first clear detection of a flattened circumstellar envelope around a Class 0 protostar, observed in absorption at 8 microns, supporting collapse theories involving magnetic fields or rotation.

Contribution

It presents the first direct imaging of a flattened protostellar envelope in absorption, providing observational evidence for theoretical models of early star formation.

Findings

Detection of a 2 arcminute flattened structure in absorption

First clear imaging of a pseudo-disk around a Class 0 protostar

Supports collapse models with magnetic fields or rotation

Abstract

Deep Spitzer IRAC images of L1157 reveal many of the details of the outflow and the circumstellar environment of this Class 0 protostar. In IRAC band 4, 8 microns, there is a flattened structure seen in absorption against the background emission. The structure is perpendicular to the outflow and is extended to a diameter of 2 arcminutes. This structure is the first clear detection of a flattened circumstellar envelope or pseudo-disk around a Class 0 protostar. Such a flattened morphology is an expected outcome for many collapse theories that include magnetic fields or rotation. We construct an extinction model for a power-law density profile, but we do not constrain the density power-law index.