Interferometric observations of nitrogen-bearing molecular species in the star-forming core ahead of HH 80N

TL;DR

This study uses interferometric observations to analyze the kinematics and chemical composition of a star-forming core near HH 80N, revealing complex dynamics, deuteration patterns, and challenging previous models of core structure and star formation triggers.

Contribution

It provides new high-resolution kinematic and chemical data of the core, refutes the molecular ring model, and suggests an evolutionary sequence inconsistent with outflow-triggered star formation.

Findings

Different kinematic signatures across the core suggest dynamical interaction with outflows.

High deuteration indicates the eastern condensation is at an earlier evolutionary stage.

The core's structure is not a molecular ring as previously thought.

Abstract

We present VLA NH3 and PdBI NH2D and H13NC observations of the star forming core ahead of HH 80N, the optically obscured northern counterpart of the Herbig-Haro objects HH 80/81. The main goal is to determine the kinematical information of the high density regions of the core ($n\lesssim 10^5$ cm$^{-3}$), missed in previous works due to the depletion of the species observed (e.g. CS). The obtained maps show different kinematical signatures between the eastern and western parts of the core, suggesting a possible dynamical interaction of the core with the HH 80/81/80N outflow. The analysis of the Position-Velocity (PV) plots of these species rules out a previous interpretation of having a molecular ring-like structure of $6\times 10^4$ AU of radius traced by CS infalling onto a central protostar found in the core (IRS1). High degree of deuteration, with respect to the central part of the core harboring IRS1, is derived in the eastern part, where a dust condensation (SE) is located. This deuteration trend of NH3 suggests that SE is in a prestellar evolutionary stage, earlier than that of the IRS1. Since SE is the closest condensation to the HH 80N/81/80N outflow, in case of having outflow-core dynamical interaction, it should be perturbed first and be the most evolved condensation in the core. Therefore, the derived evolutionary sequence for SE and IRS1 makes the outflow triggered star formation on IRS1 unlikely.