Investigating the Nested Structure of the Outflow from the Low Luminosity Protostar IRAS 16253-2429 Using JWST and ALMA

Abstract Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow, and disk evolution. We present results from the observations of the low luminosity ( L bol ∼ 0.2 L ⊙ ) and mass ( M * ∼ 0.15 M ⊙ ) Class 0 protostar IRAS 16253−2429, conducted as part of the eDisk Atacama Large Millimeter/submillimeter Array (ALMA) large program and the JWST cycle-1 GO Investigating Protostellar Accretion program. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at ≤5 μ m), with a brighter, extended northern side. We detect 15 pure rotational H 2 transitions ( E up : 1015–21411 K), revealing a wide-angle molecular outflow. The outflow width (as traced in H 2 0–0 S(11)) at the protostellar location measures ≤35 au, slightly larger than the dust and Keplerian disk diameters (∼30 au) but wider than the 20–23 au jet width in [Fe II ]. The opening angle narrows from 40° to 35° for the low-J H 2 lines (up to S(5)) and the cold gas component (ALMA 12 CO) to ∼28°–19° for the high-J H 2 lines (S(7)–S(11)). Position–velocity diagrams of H 2 reveal higher velocities for higher E up , ranging from 12.5 km s −1 for H 2 0–0 S(1) and S(2) to 28.5 km s −1 for H 2 0–0 S(5) and S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide-angle wind suggest a magnetohydrodynamic wind as a likely launching mechanism, similar to the findings in other protostars and Class II sources. The lower velocity millimeter CO may be gas from the infalling envelope accelerated outwards by the wide-angle wind along the cavity walls.