The Envelope-Disk-Outflow System in Massive Protostellar Source G339.88-1.26. (arXiv:1811.04381v1 [astro-ph.GA])

The Envelope-Disk-Outflow System in Massive Protostellar Source G339.88-1.26. (arXiv:1811.04381v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_Y/0/1/0/all/0/1">Yichen Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tan_J/0/1/0/all/0/1">Jonathan C. Tan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sakai_N/0/1/0/all/0/1">Nami Sakai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tanaka_K/0/1/0/all/0/1">Kei E. I. Tanaka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buizer_J/0/1/0/all/0/1">James M. De Buizer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_M/0/1/0/all/0/1">Mengyao Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beltran_M/0/1/0/all/0/1">Maria T. Beltran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mardones_D/0/1/0/all/0/1">Diego Mardones</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Garay_G/0/1/0/all/0/1">Guido Garay</a>

We report molecular line observations of the massive protostellar source
G339.88-1.26 with the Atacama Large Millimeter/Submillimeter Array. The
observations reveal a highly collimated SiO jet extending from the 1.3 mm
continuum source, which connects to a slightly wider but still highly
collimated CO outflow. Rotational features perpendicular to the outflow axis
are detected in various molecular emissions, including SiO, SO$_2$, H$_2$S,
CH$_3$OH, and H$_2$CO emissions. Based on their spatial distributions and
kinematics, we find that they trace different parts of the envelope-disk
system. The SiO traces the disk and inner envelope in addition to the jet, the
CH$_3$OH and H$_2$CO trace the infalling-rotating envelope outside of the disk,
and the SO$_2$ and H$_2$S appear enhanced around the transition region between
envelope and disk, i.e., the centrifugal barrier, as well as the outer part of
the disk. Envelope kinematics are consistent with rotating-infalling motion,
while those of the disk are consistent with Keplerian rotation. The radius and
velocity of the centrifugal barrier are estimated to be about 530 au and 6 km
s$^{-1}$, leading to a central mass of about $11~M_odot$, consistent with
estimates based on spectral energy distribution fitting. These results indicate
that an ordered transition from an infalling-rotating envelope to a Keplerian
disk through a centrifugal barrier, accompanied by change of chemical
composition, is a valid description of this massive protostellar source. This
implies that at least some massive stars form in a similar way as low-mass
stars via Core Accretion.

We report molecular line observations of the massive protostellar source
G339.88-1.26 with the Atacama Large Millimeter/Submillimeter Array. The
observations reveal a highly collimated SiO jet extending from the 1.3 mm
continuum source, which connects to a slightly wider but still highly
collimated CO outflow. Rotational features perpendicular to the outflow axis
are detected in various molecular emissions, including SiO, SO$_2$, H$_2$S,
CH$_3$OH, and H$_2$CO emissions. Based on their spatial distributions and
kinematics, we find that they trace different parts of the envelope-disk
system. The SiO traces the disk and inner envelope in addition to the jet, the
CH$_3$OH and H$_2$CO trace the infalling-rotating envelope outside of the disk,
and the SO$_2$ and H$_2$S appear enhanced around the transition region between
envelope and disk, i.e., the centrifugal barrier, as well as the outer part of
the disk. Envelope kinematics are consistent with rotating-infalling motion,
while those of the disk are consistent with Keplerian rotation. The radius and
velocity of the centrifugal barrier are estimated to be about 530 au and 6 km
s$^{-1}$, leading to a central mass of about $11~M_odot$, consistent with
estimates based on spectral energy distribution fitting. These results indicate
that an ordered transition from an infalling-rotating envelope to a Keplerian
disk through a centrifugal barrier, accompanied by change of chemical
composition, is a valid description of this massive protostellar source. This
implies that at least some massive stars form in a similar way as low-mass
stars via Core Accretion.

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