HERSCHEL-HIFI spectroscopy of the intermediate mass protostar NGC7129 FIRS 2

TL;DR

This study uses Herschel-HIFI spectroscopy to analyze water emission in the intermediate mass protostar NGC7129 FIRS 2, revealing envelope characteristics, outflow dynamics, and water abundance constraints in the star formation environment.

Contribution

First detailed water spectral analysis of NGC7129 FIRS 2, linking water emission features to envelope and outflow physical conditions.

Findings

Detected multiple water lines, revealing envelope and outflow components.

Estimated water abundance in the outer envelope as approximately 10^-7.

Identified a broad outflow-related component with a water/CO ratio of about 0.2.

Abstract

HERSCHEL-HIFI observations of water from the intermediate mass protostar NGC7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four H216O and two H218O lines, were observed and all but one H218O line were detected. The four H2 16 O lines discussed here share a similar morphology: a narrower, \approx 6 km/s, component centered slightly redward of the systemic velocity of NGC7129 FIRS 2 and a much broader, \approx 25 km/s component centered blueward and likely associated with powerful outflows. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H2O is constrained to \approx 10-7 for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope. The broader component, where the H2O/CO relative abundance is found to be \approx 0.2, appears to be tracing the same energetic region that produces strong CO emission at high J.