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

الأصل · EN

We present high angular resolution (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 (CH₃SH). At scales larger than 10,000 AU, molecules (e.g., SO₂ or OCS) mostly with low excitation temperatures in the upper states (Eₖ 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 (Eₖ 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, which is consistent with the bolometric luminosity of IRAS 16547-4247.