The Disk–Outflow System around the Rare Young O-type Protostar W42-MME

Abstract

Abstract We present line and continuum observations (resolution ∼0.″3–3.″5) made with the Atacama Large Millimeter/submillimeter Array (ALMA), Submillimeter Array, and Very Large Array of a young O-type protostar W42-MME (mass: 19 ± 4 M ⊙). The ALMA 1.35 mm continuum map (resolution ∼1″) shows that W42-MME is embedded in one of the cores (i.e., MM1) located within a thermally supercritical filament-like feature (extent ∼0.15 pc) containing three cores (mass ∼1–4.4 M ⊙). Several dense/hot gas tracers are detected toward MM1, suggesting the presence of a hot molecular core with a gas temperature of ∼38–220 K. The ALMA 865 μm continuum map (resolution ∼0.″3) reveals at least five continuum sources/peaks (A–E) within a dusty envelope (extent ∼9000 au) toward MM1, where shocks are traced in the SiO (8–7) emission. Source A associated with W42-MME is seen almost at the center of the dusty envelope and is surrounded by other continuum peaks. The ALMA CO (3–2) and SiO (8–7) line observations show the bipolar outflow extended below 10,000 au, which is driven by source A. The ALMA data hint at the episodic ejections from W42-MME. A disk-like feature (extent ∼2000 au, mass ∼1 M ⊙) with velocity gradients is investigated in source A (dynamical mass ∼9 M ⊙) using the ALMA H13CO+ emission, and it is perpendicular to the CO outflow. A small-scale feature (below 3000 au), probably heated by UV radiation from the O-type star, is also investigated toward source A. Overall, W42-MME appears to gain mass from its disk and the dusty envelope.