The standard model of low-mass star formation applied to massive stars: multi-wavelength modelling of IRAS 20126+4104

TL;DR

This study applies a low-mass star formation model to a massive star, IRAS 20126+4104, using multi-wavelength data and radiative transfer simulations to understand its structure and formation process.

Contribution

It demonstrates that a standard envelope plus disc model effectively describes the massive star's observed properties, extending low-mass star formation theories to high-mass stars.

Findings

Envelope plus disc model fits observed SED and images better.

Disc radius estimated at 9200 au, stable against fragmentation.

Mid-IR morphology suggests possible inner disc truncation or outflow precession.

Abstract

In order to investigate whether massive stars form similarly to their low-mass counterparts, we have used the standard envelope plus disc geometry successfully applied to low-mass protostars to model the near-IR to sub-millimetre SED and several mid-IR images of the embedded massive star IRAS20126+4104. We have used a Monte Carlo radiative transfer dust code to model the continuum absorption, emission and scattering through two azimuthally symmetric dust geometries, the first consisting of a rotationally flattened envelope with outflow cavities, and the second which also includes a flared accretion disc. Our results show that the envelope plus disc model reproduces the observed SED and images more accurately than the model without a disc, although the latter model more closely reproduces the morphology of the mid-IR emission within a radius of 1.1" or ~1800au. We have put forward several possible causes of this discontinuity, including inner truncation of the disc due to stellar irradiation, or precession of the outflow cavity. Our best fitting envelope plus disc model has a disc radius of 9200 au. We find that it is unlikely that the outer regions of such a disc would be in hydrostatic or centrifugal equilibrium, however we calculate that the temperatures within the disc would keep it stable to fragmentation.