The Asymmetric Bipolar Fe II Jet and H2 Outflow of TMC1A Resolved with JWST's NIRSpec IFU

TL;DR

This study uses JWST's NIRSpec IFU to resolve the detailed structure of the bipolar Fe II jet and H2 outflow in the Class I protostar TMC1A, revealing new spatial features, asymmetries, and a possible molecular jet.

Contribution

First detection of a red-shifted atomic Fe II jet and a collimated high-velocity H2 outflow in TMC1A using JWST, providing new insights into protostellar outflow asymmetries.

Findings

Red-shifted Fe II and H2 emissions are weaker than blue-shifted counterparts.

Detection of a high-velocity (100 km/s) blue-shifted H2 outflow suggesting a molecular jet.

H2 wide-angle outflow exhibits a 'ring'-like structure and brightness asymmetry.

Abstract

(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.