Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects. I. Revisiting the high-mass protostar W33A

TL;DR

This study uses principal component analysis tomography on near-infrared data to reveal a more compact rotating disc around the high-mass protostar W33A, identifying multiple protostars and outflows in its vicinity.

Contribution

It introduces an advanced post-processing approach to analyze integral field spectroscopy data, providing new insights into the structure and dynamics of W33A and its environment.

Findings

Detected a compact rotating disc with a radius of ~250 AU.

Derived a dynamical mass of approximately 10 solar masses.

Identified multiple protostars and outflows near W33A.

Abstract

W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the $K$-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position-velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0\farcs1 ($\sim$250 AU) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ M$_\odot$ for the "disc+protostar" system, about $\sim$33% smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H$_2$ wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of $\sim$63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of $\sim$7,000 AU from W33A, powering extended $K$-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar H$_2$ jet aligned perpendicular to the rotation axis of W33A.