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

Context. Protostellar outflows exhibit large variations in their structure depending on the observed gas emission. To understand the origin of the observed variations, it is important to analyze differences in the observed morphology and kinematics of the differ- ent tracers. The James Webb Space Telescope (JWST) allows us to study the physical structure of the protostellar outflow through well-known near-infrared shock tracers in a manner unrivaled by other existing ground-based and space-based telescopes at these wavelengths. Aims. This study analyzes the atomic jet and molecular outflow in the Class I protostar, TMC1A, utilizing spatially resolved [Fe ii] and H2 lines to characterize morphology and identify previously undetected spatial features, and compare them to existing observations of TMC1A and its outflows observed at other wavelengths. Methods. We identify a large number of [Fe ii] and H2 lines within the G140H, G235H, and G395H gratings of the NIRSpec IFU observations. We analyze their morphology and position-velocity (PV) diagrams. From the observed [Fe ii] line ratios, the extinction toward the jet is estimated. Results. 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 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 older Class II jets.