A detailed study of the accretion disk surrounding the high-mass protostar NGC 7538S

TL;DR

This study provides high-resolution observations of the high-mass protostar NGC 7538S, revealing a compact, rotating accretion disk with high accretion rates and detailed molecular tracers, advancing understanding of massive star formation.

Contribution

It offers the first detailed high-resolution imaging of the disk structure and rotation around NGC 7538S, refining previous estimates of disk size and mass, and analyzing molecular tracers affected by outflows.

Findings

The accretion disk is smaller than previously estimated.

The inner disk mass is approximately 14-24 solar masses.

Molecular tracers show evidence of disk rotation and outflow influence.

Abstract

We present deep high angular resolution observations of the high-mass protostar NGC 7538S, which is in the center of a cold dense cloud core with a radius of 0.5 pc and a mass of ~2,000 Msun. These observations show that NGC 7538S is embedded in a compact elliptical core with a mass of 85 - 115 Msun. The star is surrounded by a rotating accretion disk, which powers a very young, hot molecular outflow approximately perpendicular to the rotating accretion disk. The accretion rate is very high, ~ 1.4 - 2.8 10^-3 Msun yr^-1. Evidence for rotation of the disk surrounding the star is seen in all largely optically thin molecular tracers, H13CN J = 1-0, HN13C J = 1-0, H13CO+ J = 1-0, and DCN J = 3-2. Many molecules appear to be affected by the hot molecular outflow, including DCN and H13CO+. The emission from CH3CN, which has often been used to trace disk rotation in young high-mass stars, is dominated by the outflow, especially at higher K-levels. Our new high-angular resolution observations show that the rotationally supported part of the disk is smaller than we previously estimated. The enclosed mass of the inner, rotationally supported part of the disk (D ~ 5", i.e 14,000 AU) is ~ 14 - 24 Msun.