ATCA 3mm observations of NGC6334I and I(N): dense cores, outflows and an UCHII region

TL;DR

This study uses ATCA at 3mm to analyze dense gas, outflows, and continuum emission in the massive cores NGC6334I and I(N), revealing potential accretion disk signatures and complex outflow dynamics.

Contribution

First high-resolution ATCA observations of NGC6334I and I(N) that identify dense cores, outflows, and possible accretion disk signatures, advancing understanding of massive star formation.

Findings

Detection of line emission from protostellar condensations in NGC6334I(N)

Identification of a velocity gradient suggestive of an accretion disk in NGC6334I

Observation of precessing outflows and broad HCN absorption lines

Abstract

Aims: Investigation of the dense gas, the outflows and the continuum emission from the massive twin cores NGC6334I and I(N) at high spatial resolution. Methods: We imaged the region with the Australia Telescope Compact Array (ATCA) at 3.4mm wavelength in continuum as well as CH3CN(5_K-4_K) and HCN(1-0) spectral line emission. Results: While the continuum emission in NGC6334I mainly traces the UCHII region, toward NGC6334I(N) we detect line emission from four of the previously identified dust continuum condensations that are of protostellar or pre-stellar nature. The CH3CN(5_K-4_K) lines are detected in all K-components up to energies of 128K above ground toward two protostellar condensations in both regions. We find line-width increasing with increasing K for all sources, which indicates a higher degree of internal motions closer to the central protostars. Toward the main mm and CH3CN source in NGC6334I we identify a velocity gradient approximately perpendicular to the large-scale molecular outflow. This may be interpreted as a signature of an accretion disk, although other scenarios, e.g., an unresolved double source, could produce a similar signature as well. No comparable signature is found toward any of the other sources. HCN does not trace the dense gas well but it is dominated by the molecular outflows. While the outflow in NGC6334I exhibits a normal Hubble-law like velocity structure, the data indicate a precessing outflow close to the plane of the sky for NGC6334I(N). Furthermore, we observe a wide (~15.4km/s) HCN absorption line, much broader than the previously observed CH3OH and NH3 absorption lines. Several explanations for the difference are discussed.