Spiral arm, rotating structure, and outflow cavity in massive star-forming region G23.43−0.18

Abstract

ABSTRACT We confirmed the existence of a massive protocluster in G23.43−0.18 from our Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum and molecular line observations. We resolved the region into one main massive protostellar object, G23.43−0.18 A, one intermediate mass protostellar object, G23.43−0.18 B, and three low mass objects, G23.43−0.18 C1, G23.43–0.18 C2, and G23.43−0.18 C3. A spiral arm structure is observed in G23.43−0.18 B. G23.43−0.18 A 1.3 mm dust continuum emission showed a ‘butterfly’ morphology with clear evidence of the existence of a cavity and bipolar outflow with an inclination angle of 50$^\circ$. G23.43−0.18 B presents a compact rotating structure, and possibly an inner Keplerian disc, traced with methanol lines and powers a jet revealed by multiple compact emission peaks in CO, indicating episodic ejections every 300 yr. The presence of 6.7 GHz methanol masers in G23.43−0.18 A and G23.43−0.18 B are strong indications that both objects host massive protostars and are good sites to test some theories of the early evolutionary phases of massive stars.