Discovery of a sub-Keplerian disk with jet around a 20 M_⊙ young star

Abstract

It is well established that Solar-mass stars gain mass via disk accretion, until the mass reservoir of the disk is exhausted and dispersed, or condenses into planetesimals. Accretion disks are intimately coupled with mass ejection via polar cavities, in the form of jets and less collimated winds, which allow mass accretion through the disk by removing a substantial fraction of its angular momentum. Whether disk accretion is the mechanism leading to the formation of stars with much higher masses is still unclear. Here, we are able to build a comprehensive picture for the formation of an O-type star, by directly imaging a molecular disk which rotates and undergoes infall around the central star, and drives a molecular jet which arises from the inner disk regions. The accretion disk is truncated between 2000-3000 au, it has a mass of about a tenth of the central star mass, and is infalling towards the central star at a high rate (6 × 10 −4 M yr −1 ), as to build up a very massive object. These findings, obtained with the Atacama Large Millimeter/submillimeter Array at 700 au resolution, provide observational proof that young massive stars can form via disk accretion much like Solar-mass stars.

H II regions and high-mass starless clump candidates

“…This publication is based on the SEDIGISM and PPMAP data. models for HMSF have been discussed widely: (1) monolithic collapse (McKee & Tan 2003;Krumholz et al 2009;Csengeri et al 2018;Sanna et al 2019;Motogi et al 2019) and (2) competitive accretion Cyganowski et al 2017;Fontani et al 2018). It is possible that these models are not strongly and mutually incompatible as described by many current studies; these two models of HMSF are expected to be merged into a unified and consistent star formation model with the progress of observations and theories (Schilke 2015).…”

Disc kinematics and stability in high-mass star formation

“…This is in part due to their scarcity, fast evolution, and the fact that high-mass stars form in dense distant clusters, making disentangling individual stellar contributions difficult (see review by Motte et al 2018). Perhaps the best observational evidence for the existence of disks is the ubiquitous observations of collimated bipolar outflows (e.g., Beuther et al 2002;Fallscheer et al 2009;Leurini et al 2011;Frank et al 2014;Maud et al 2015;Sanna et al 2019), which has also been predicted by theoretical models (e.g., Pudritz et al 2007;Banerjee & Pudritz 2008;Kölligan & Kuiper 2018). A review by Beltrán & de Wit (2016) summarises our current understanding of the properties of accretion disks around young intermediate-to high-mass stars.…”

A Detailed View of the Circumstellar Environment and Disk of the Forming O-star AFGL 4176

“…While several sources typify the picture of a scaled-up version of a disk around a low-mass star (e.g. AFGL 4176, G11.92-0.61 MM1, IRAS 18162-2048 or GGD27 MM1, G023.01-00.41, and G339.88-1.26; J15, Ilee et al 2016;Girart et al 2018;Sanna et al 2019;Zhang et al 2019b), there are in fact a range of disk morphologies found toward high-mass stars. These can include multipledisk systems (e.g.…”

“…This was caused by observational difficulties due to their relative rarity and thus larger distances, and the fact that massive forming stars are often observed in highly clustered environments, which, combined with a lack of sufficient angular resolution, made the study of these objects challenging. This was followed recently by the first discoveries of disks around O-type stars (Kraus et al 2010;Jiménez-Serra et al 2012;Wang et al 2012;Johnston et al 2015;Ilee et al 2016;Cesaroni et al 2017;Zapata et al 2019;Sanna et al 2019). As disks provide a conduit for accretion that has a small solid angle as viewed from the star, they are a particularly essential ingredient in the theory of massive star formation, as they are needed to overcome the large amount of radiation pressure that, in the case of spherical accretion, would impede the accretion of material onto massive stars, and thus halt their formation (e.g.…”