Detecting Infall in High-Mass Protostellar Objects

TL;DR

This paper discusses methods to detect infall in high-mass protostellar objects, aiming to provide definitive evidence of accretion processes in massive star formation using advanced radio observations.

Contribution

It proposes a new approach to characterize infall in high-mass star-forming regions with the next-generation Very Large Array (ngVLA), covering a broad luminosity range.

Findings

Sample of 36 high-mass accretion disk candidates analyzed

Methodology to detect infall signatures in high-mass protostars

Potential to unambiguously confirm accretion in massive star formation

Abstract

The role of accretion disks in the formation of low-mass stars has been well assessed by means of high angular resolution observations at various wavelengths. These findings confirm the prediction that conservation of angular momentum during the collapse leading to the formation of a star is bound to produce flattening and rotation of the collapsing core. What about high-mass stars? At present, several authors have reported on detections of disks around high-mass YSOs. Notwithstanding these important results, the presence of disks rotating about high-mass stars is not sufficient by itself to prove unambiguously the accretion model: what is needed is iron-clad evidence of infall. Such evidence is very difficult to find, as the free-fall velocity becomes significant only very close to the accreting star, i.e., over a region of a few 0.01 pc ($\sim$2000 au), which is very difficult to access and disentangle from the surrounding quiescent or rotating material. In this chapter we discuss how to characterize the infall of material in a sample of 36 high-mass accretion disk candidates covering a broad range of luminosities, from 10$^3$ $L_\odot$ to 10$^6$ $L_\odot$, compiled by Beltr\'an & de Wit (2016) with the next generation Very Large Array (ngVLA).