ALMA reveals a candidate hot and compact disk around the O-type protostar IRAS 16547$-$4247

Abstract

We present high angular resolution ($\sim$ 0.3$"$) submillimeter continuum (0.85 mm) and line observations of the O-type protostar IRAS 16547$-$4247 carried out with the Atacama Large Millimeter/Submillimeter Array (ALMA). In the 0.85 mm continuum band, the observations revealed two compact sources (with a separation of 2$"$), one of them associated with IRAS 16547$-$4247, and the other one to the west. Both sources are well resolved angularly, revealing a clumpy structure. On the other hand, the line observations revealed a rich variety of molecular species related to both continuum sources. In particular, we found a large number of S-bearing molecules, such as the rare molecule methyl mercaptan (CH${}_3$SH). At scales larger than 10,000 AU, molecules (e.g., SO${}_2$ or OCS) mostly with low excitation temperatures in the upper states (E${}_k$ $\lesssim$ 300 K) are present in both millimeter continuum sources, and show a southeast-northwest velocity gradient of 7 km s${}^{-1}$ over 3$"$ (165 km s${}^{-1}$ pc${}^{-1}$). We suggest that this gradient probably is produced by the thermal (free-free) jet emerging from this object with a similar orientation at the base. At much smaller scales (about 1000 AU), molecules with high excitation temperatures (E${}_k$ $\gtrsim$ 500 K) are tracing a rotating structure elongated perpendicular to the orientation of the thermal jet, which we interpret as a candidate disk surrounding IRAS 16547$-$4247. The dynamical mass corresponding to the velocity gradient of the candidate to disk is about 20 M${}_{\odot }$, which is consistent with the bolometric luminosity of IRAS 16547$-$4247.

Accepted by MNRAS

References in corpus (5)

• Circumventing the radiation pressure barrier in the formation of massive stars via disk accretion
• The Collimated Jet Source in IRAS 16547-4247: Time Variation, Possible Precession, and Upper Limits to the Proper Motions Along the Jet Axis
• Gamma-ray emission from massive young stellar objects
• A multiple system of high-mass YSOs surrounded by disks in NGC7538 IRS1
• The Rotating Molecular Structures and the Ionized Outflow Associated with IRAS 16547-4247

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• An Asymmetric Keplerian Disk Surrounding the O-type Protostar IRAS16547$-$4247
• Salt, Hot Water, and Silicon Compounds Tracing Massive Twin Disks
• Disk Kinematics and Stability in High-Mass Star Formation: Linking Simulations and Observations
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• ALMA observations of the Extended Green Object G19.01$-$0.03: I. A Keplerian disc in a massive protostellar system
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