The Asymmetric Bipolar Fe II Jet and H2 Outflow of TMC1A Resolved with JWST's NIRSpec IFU
arxiv(2024)
摘要
(abridged) Protostellar outflows exhibit large variations in their structure
depending on the observed gas emission. This study analyzes the atomic jet and
molecular outflow in the Class I protostar, TMC1A to characterize morphology
and identify previously undetected spatial features with JWST's NIRSpec IFU. In
addition to identifying a large number of Fe II and H2 lines, we have detected
the bipolar Fe jet by revealing, for the first time, the presence of a
red-shifted atomic jet. Similarly, the red-shifted component of the H2 slower
wide-angle outflow is observed. Both Fe II and H2 red-shifted emission exhibit
significantly lower flux densities compared to their blue-shifted counterparts.
Additionally, we report the detection of a collimated high-velocity (100 km
s-1), blue-shifted H2 outflow, suggesting the presence of a molecular jet in
addition to the well-known wider angle low-velocity structure. The Fe II and H2
jets show multiple intensity peaks along the jet axis, which may be associated
with ongoing or recent outburst events. In addition to the variation in their
intensities, the H2 wide-angle outflow exhibits a "ring"-like structure. The
blue-shifted H2 outflow also shows a left-right brightness asymmetry likely due
to interactions with the surrounding ambient medium and molecular outflows.
Using the Fe II line ratios, the extinction along the atomic jet is estimated
to be between Av = 10-30 on the blue-shifted side, with a trend of decreasing
extinction with distance from the protostar. A similar Av is found for the
red-shifted side, supporting the argument for an intrinsic red-blue outflow
lobe asymmetry rather than environmental effects such as extinction. This
intrinsic difference revealed by the unprecedented sensitivity of JWST,
suggests that younger outflows already exhibit the red-blue side asymmetry more
commonly observed towards jets associated with Class II disks.
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