Subarcsecond Imaging of the NGC 6334 I(N) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate

TL;DR

This study provides high-resolution imaging of the NGC 6334 I(N) protocluster, revealing 25 members, hot cores, a potential massive disk, and masers, advancing understanding of massive star formation in dense clusters.

Contribution

First high-resolution subarcsecond imaging of NGC 6334 I(N) revealing 25 protostellar sources, hot cores, and a candidate massive disk, with detailed kinematic and spectral analysis.

Findings

Detected 18 new compact sources in the protocluster.

Identified a rotating, infalling Keplerian disk around SMA1b.

Measured a protocluster dynamical mass of approximately 410 solar masses.

Abstract

Using the SMA and VLA, we have imaged the massive protocluster NGC6334I(N) at high angular resolution (0.5"~650AU) from 6cm to 0.87mm, detecting 18 new compact continuum sources. Three of the new sources are coincident with previously-identified water masers. Together with the previously-known sources, these data bring the number of likely protocluster members to 25 for a protostellar density of ~700 pc^-3. Our preliminary measurement of the Q-parameter of the minimum spanning tree is 0.82 -- close to the value for a uniform volume distribution. All of the (nine) sources with detections at multiple frequencies have SEDs consistent with dust emission, and two (SMA1b and SMA4) also have long wavelength emission consistent with a central hypercompact HII region. Thermal spectral line emission, including CH3CN, is detected in six sources: LTE model fitting of CH3CN(J=12-11) yields temperatures of 72-373K, confirming the presence of multiple hot cores. The fitted LSR velocities range from -3.3 to -7.0 km/s, with an unbiased mean square deviation of 2.05 km/s, implying a dynamical mass of 410+-260 Msun for the protocluster. From analysis of a wide range of hot core molecules, the kinematics of SMA1b are consistent with a rotating, infalling Keplerian disk of diameter 800AU and enclosed mass of 10-30 Msun that is perpendicular (within 1 degree) to the large-scale bipolar outflow axis. A companion to SMA1b at a projected separation of 0.45" (590AU; SMA1d), which shows no evidence of spectral line emission, is also confirmed. Finally, we detect one 218.440GHz and several 229.7588GHz Class-I methanol masers.