ALMA discovery of a dual dense probably rotating outflow from a massive
  young stellar object G18.88MME
  We report the discovery of a very dense jet-like fast molecular outflow
surrounded by a wide-angle wind in a massive young stellar object (MYSO)
G18.88MME (stellar mass $\sim$8 M$_{\odot}$) powering an Extended Green Object
G18.89$-$0.47. Four cores MM1-4 are identified in the Atacama Large
Millimeter/submillimeter Array (ALMA) 1.3 mm continuum map (resolution
$\sim$0.$"$8) toward G18.88MME, and are seen at the center of the emission
structure (extent $\sim$0.3 pc $\times$ 0.2 pc) detected in the ALMA map.
G18.88MME is embedded in the core MM1 (mass $\sim$13-18 M$_{\odot}$), where no
radio continuum emission is detected. The molecular outflow centered at MM1 is
investigated in the SiO(5-4), HC$_{3}$N(24-23) and $^{13}$CO(2-1) lines. The
detection of HC$_{3}$N in the outflow is rare in MYSOs and indicates its very
high density. The position-velocity diagrams display a fast narrow outflow
(extent $\sim$28000 AU) and a slower wide-angle more extended outflow toward
MM1, and both of these components show a transverse velocity gradient
indicative of a possible rotation. All these observed features together make
G18.88MME as a unique object for studying the unification of the jet-driven and
wind-driven scenarios of molecular outflows in MYSOs.
