10 research outputs found
The Molecular Accretion Flow in G10.6-0.4
We have observed the ultracompact HII region G10.6-0.4 with the VLA in 23 GHz
continuum and the NH3(3,3) inversion line. By analyzing the optical depth of
the line as well as the kinematics, we have detected a flattened, rotating,
molecular accretion flow. We detect the fact that the highest column density
gas is more flattened, that is, distributed more narrowly, than the lower
column density gas, and that there is some inclination of the rotation axis.
The rotation is sub-Keplerian, and the molecular gas is not in a rotationally
supported disk. We do not find a single massive (proto)star forming in a scaled
up version of low mass star formation. Instead, our observations suggest a
different mode of clustered massive star formation, in which the accretion flow
flattens but does not form an accretion disk. Also in this mode of star
formation the central object can be a group of massive stars rather than a
single massive star.Comment: 20 pages, 6 figures Accepted for publication in the Astrophysical
Journa
Experimental Observation Of Correlated Magnetic Reconnection And Alfvénic Ion Jets
Correlations between magnetic reconnection and energetic ion flow events have been measured with merging force free spheromaks at the Swarthmore Spheromak Experiment. The reconnection layer is measured with a linear probe array and ion flow is directly measured with a retarding grid energy analyzer. Flow has been measured both in the plane of the reconnection layer and out of the plane. The most energetic events occur in the reconnection plane immediately after formation as the spheromaks dynamically merge. The outflow velocity is nearly Alfvenic. As the spheromaks form equilibria and decay, the flow is substantially reduced
Spherical Infall in G10.6-0.4: Accretion Through an Ultracompact HII Region
We present high resolution (0.''12 x 0.''079) observations of the
ultracompact HII region G10.6-0.4 in 23 GHz radio continuum and the NH3(3,3)
line. Our data show that the infall in the molecular material is largely
spherical, and does not flatten into a molecular disk at radii as small as 0.03
pc. The spherical infall in the molecular gas matches in location and velocity
the infall seen in the ionized gas. We use a non-detection to place a stringent
upper limit on the mass of an expanding molecular shell associated with
pressure driven expansion of the HII region. These data support a scenario in
which the molecular accretion flow passes through an ionization front and
becomes an ionized accretion flow onto one or more main sequence stars, not the
classical pressure-driven expansion scenario. In the continuum emission we see
evidence for externally ionized clumps of molecular gas, and cavities evacuated
by an outflow from the central source.Comment: Accepted for publication in Astrophysical Journal Letter
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