Feedback of molecular outflows from protostars in NGC 1333, revealed by Herschel and Spitzer spectro-imaging observations

TL;DR

This study uses spectral-line maps from Herschel and Spitzer to analyze gas excitation, kinematics, and water abundance in protostellar outflows in NGC 1333, revealing complex physical processes and shock interactions.

Contribution

It provides a comprehensive multi-line analysis of outflows in NGC 1333, comparing excitation, morphology, and abundance of different tracers with new insights into shock processes.

Findings

H$_2$ and CO trace protostellar outflows at different excitation levels.

Water emission is dominated by outflow-related shocks and varies in abundance.

Outflow mass flux is highest for CO, lower for H$_2$ and H$_2$O.

Abstract

Large scale spectral maps of star forming regions enable the comparative study of the gas excitation around an ensemble of sources at a common frame of reference, providing direct insights in the multitude of processes involved. In this paper we employ spectral-line maps to decipher the excitation, the kinematical and dynamical processes in NGC 1333 as revealed by a number of different emission lines, aiming to set a reference for the applicability of tracers in constraining diverse physical processes. We reconstruct line maps for H$_2$ , CO, H$_2$O and C$^+$ using data obtained with the Spitzer-IRS and Herschel HIFI-SPIRE. We compare the morphological features of the maps and derive the gas excitation for regions of interest employing LTE and non-LTE methods. We also calculate the kinematical and dynamical properties for each outflow tracer consistently for all outflows in NGC 1333. We finally measure the water abundance in outflows with respect to carbon monoxide and molecular hydrogen. CO and H$_2$ are highly excited around B-stars and at lower levels trace protostellar outflows. H$_2$O emission is dominated by a moderately fast component associated with outflows. Intermediate J CO lines appear brightest at the locations traced by a narrow H$_2$O component, indicating that beyond the dominating collisional processes, a secondary, radiative excitation component can also be active. The morphology, kinematics, excitation and abundance variations of water are consistent with its excitation and partial dissociation in shocks. Water abundance ranges between 5 x 10$^{-7}$ and 10$^{-5}$, with the lower values being more representative. Water is brightest and most abundant around IRAS 4A which is consistent with the latter hosting a hot corino source. Finally, the outflow mass flux is found highest for CO and decreases by one and two orders of magnitude for H$_2$ and H$_2$O, respectively.