Energetic processes revealed by spectrally resolved high-J CO lines in low-mass star-forming regions with Herschel-HIFI

TL;DR

This study uses Herschel-HIFI high-J CO line observations to investigate energetic processes in low-mass star-forming regions, revealing evidence of CO ice evaporation zones and different gas components.

Contribution

It provides the first direct evidence of a CO ice evaporation zone around low-mass protostars through spectrally resolved high-J CO lines and radiative transfer modeling.

Findings

Detection of shocked and quiescent gas components.

Identification of a CO ice evaporation zone at ~25 K.

Inner envelope CO abundance is significantly lower than outer regions.

Abstract

Herschel-HIFI observations of high-J lines (up to J_u=10) of 12CO, 13CO and C18O are presented toward three deeply embedded low-mass protostars in NGC1333. The observations show several energetic components including shocked and quiescent gas. Radiative transfer models are used to quantify the C18O envelope abundance which require a jump in the abundance at an evaporation temperature, T_ev ~25 K, providing new direct evidence of a CO ice evaporation zone around protostars. The abundance in the outermost part of the envelope, X_0, is within the canonical value of 2x10^-4; however the inner abundance, X_in, is found around a factor of 3-5 lower than X_0.