The circumestellar disk of the B0 protostar powering the HH 80-81 radio jet

TL;DR

This study uses high-resolution submillimeter observations to characterize the disk structure and kinematics around the B0 protostar GGD27 MM1, revealing a rotating disk with specific physical parameters and chemical signatures.

Contribution

First detailed modeling of the disk around GGD27 MM1 using SMA data, including kinematic analysis and chemical composition insights.

Findings

Disk exhibits Keplerian rotation with a 4-18 solar mass protostar.

Sulfur-bearing molecules trace shock or hot core conditions.

Disk radius estimated between 950-1300 AU.

Abstract

We present subarcsecond angular resolution observations carried out with the Submillimeter Array (SMA) at 880 $\mu$m centered at the B0-type protostar GGD27~MM1, the driving source of the parsec scale HH 80-81 jet. We constrain its polarized continuum emission to be $\lesssim0.8\%$ at this wavelength. Its submm spectrum is dominated by sulfur-bearing species tracing a rotating disk--like structure (SO and SO$_2$ isotopologues mainly), but also shows HCN-bearing and CH$_3$OH lines, which trace the disk and the outflow cavity walls excavated by the HH 80-81 jet. The presence of many sulfurated lines could indicate the presence of shocked gas at the disk's centrifugal barrier or that MM1 is a hot core at an evolved stage. The resolved SO$_2$ emission traces very well the disk kinematics and we fit the SMA observations using a thin-disk Keplerian model, which gives the inclination (47$^{\circ}$), the inner ($\lesssim170$ AU) and outer ($\sim950-1300$~AU) radii and the disk's rotation velocity (3.4 km s$^{-1}$ at a putative radius of 1700 AU). We roughly estimate a protostellar dynamical mass of 4-18\msun. MM2 and WMC cores show, comparatively, an almost empty spectra suggesting that they are associated with extended emission detected in previous low-angular resolution observations, and therefore indicating youth (MM2) or the presence of a less massive object (WMC).