Multi-wavelength modelling of the circumstellar environment of the massive proto-star AFGL 2591 VLA 3

TL;DR

This study models the dust and gas environment of the massive young star AFGL 2591 using multi-wavelength data and radiative transfer, revealing insights into its structure and dynamics, but also highlighting limitations in current models.

Contribution

First comprehensive 2-D axi-symmetric model of AFGL 2591 combining multi-wavelength observations and radiative transfer, identifying physical processes affecting envelope rotation.

Findings

Dust emission extended along outflow direction

Model explains dust continuum but not kinematic features

Disc mass estimated at 6 M_sun and radius 2200 au

Abstract

We have studied the dust density, temperature and velocity distributions of the archetypal massive young stellar object (MYSO) AFGL 2591. Given its high luminosity ($L=2 \times 10^5$ L$_\odot$) and distance ($d=3.3$ kpc), AFGL 2591 has one of the highest $\sqrt{L}/d$ ratio, giving better resolved dust emission than any other MYSO. As such, this paper provides a template on how to use resolved multi-wavelength data and radiative transfer to obtain a well-constrained 2-D axi-symmetric analytic rotating infall model. We show for the first time that the resolved dust continuum emission from Herschel 70 $\mu$m observations is extended along the outflow direction, whose origin is explained in part from warm dust in the outflow cavity walls. However, the model can only explain the kinematic features from CH$_3$CN observations with unrealistically low stellar masses ($<15$ M$_\odot$), indicating that additional physical processes may be playing a role in slowing down the envelope rotation. As part of our 3-step continuum and line fitting, we have identified model parameters that can be further constrained by specific observations. High-resolution mm visibilities were fitted to obtain the disc mass (6 M$_\odot$) and radius (2200 au). A combination of SED and near-IR observations were used to estimate the luminosity and envelope mass together with the outflow cavity inclination and opening angles.