A disk of dust and molecular gas around a high-mass protostar

Abstract

The processes leading to the birth of low-mass stars such as our Sun have been well studied, but the formation of high-mass (> 8 x Sun's mass) stars has heretofore remained poorly understood. Recent observational studies suggest that high-mass stars may form in essentially the same way as low-mass stars, namely via an accretion process, instead of via merging of several low-mass (< 8 Msun) stars. However, there is as yet no conclusive evidence. Here, we report the discovery of a flattened disk-like structure observed at submillimeter wavelengths, centered on a massive 15 Msun protostar in the Cepheus-A region. The disk, with a radius of about 330 astronomical units (AU) and a mass of 1 to 8 Msun, is detected in dust continuum as well as in molecular line emission. Its perpendicular orientation to, and spatial coincidence with the central embedded powerful bipolar radio jet, provides the best evidence yet that massive stars form via disk accretion in direct analogy to the formation of low-mass stars

High-resolution mm interferometry and the search for massive protostellar disks: the case of Cep-A HW2

“…1 with a dashed line) reveals a velocity spread of about 6 km s −1 (see Fig. 2), also observed by Patel et al (2005). However, the two intensity peaks along the axis share the same systemic velocity (∼−5 km s −1 ).…”

“…However, the G99 data did not have enough spatial and spectral resolution to establish a kinematical proof of a disk, and the water masers in T96 share the ambiguity of most similar studies about what the masers actually trace. Based on SMA observations of CH 3 CN and dust emission, Patel et al (2005) have recently claimed the presence of an 8 M rotating disk, accreting onto HW2, and extending for about 330 AU around the protostar. Our PdBI observations do not support this interpretation: our conclusion is that, on the 1 scale, the Cep-A "disk" is actually the superposition of at least three different hot-core-type sources, at least one of them being the exciting source for a second molecular outflow.…”

SMA observations of the W3(OH) complex: Dynamical differentiation between W3(H2O) and W3(OH)

“…Outflows are frequently detected in high-mass star forming regions, but it is thought that high-mass star formation is not merely a scaled-up version of the low-mass star formation process characterized by larger outflow parameters (e. g., Wu et al 2004), poor collimation around massive young stars (e. g., Shepherd & Churchwell 1996;Zhang et al 2005) and higher accretion rates (see review by Zinnecker & Yorke 2007). Additionally, disks in high-mass young stellar objects are still elusive -only a few of them have been detected (Zhang ⋆ E-mail: slqin@bao.ac.cn Shepherd, Claussen & Kurtz 2001;Patel et al 2005;Jiang et al 2005;Sánchez-Monge et al 2013a -probably due to their short lifetimes, the necessity of achieving high angular resolution (not available in the observations prior to ALMA) and source confusion in dense clusters. Therefore, the study and characterization of the outflow and infall processes involved in the formation of high-mass stars need to be understood in more detail.…”

Millimetre spectral line mapping observations towards four massive star-forming H ii regions

“…There is a fast, bipolar, highly collimated radio jet ejected from the HW2 young stellar object (YSO), with well-aligned NE-SW direction and a scale of ∼1500 au (Curiel et al 2006). Furthermore, a rotating disc around HW2 has been identified from submillimetre observations (Patel et al 2005). …”