Water emission in NGC1333-IRAS4: The physical structure of the envelope

TL;DR

This study analyzes far-infrared water emission in the NGC1333-IRAS4 protostellar system, modeling the envelope to explain observed water lines and assessing the emission's origin.

Contribution

The paper presents a detailed model of the protostellar envelope that explains water emission lines observed by ISO-LWS, supporting the envelope origin hypothesis.

Findings

Water emission can be explained by the envelope model.

The model predicts density, mass accretion rate, and water abundance consistent with previous studies.

Envelope emission is a plausible source of observed water lines.

Abstract

We report ISO-LWS far infrared observations of CO, water and oxygen lines towards the protobinary system IRAS4 in the NGC1333 cloud. We detected several water, OH, CO rotational lines, and two [OI] and [CII] fine structure lines. Given the relatively poor spectral and spatial resolution of these observations, assessing the origin of the observed emission is not straightforward. In this paper, we focus on the water line emission and explore the hypothesis that it originates in the envelopes that surround the two protostars, IRAS4 A and B, thanks to an accurate model. The model reproduces quite well the observed water line fluxes, predicting a density profile, mass accretion rate, central mass, and water abundance profile in agreement with previous works. We hence conclude that the emission from the envelopes is a viable explanation for the observed water emission, although we cannot totally rule out the alternative that the observed water emission originates in the outflow.