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

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 ($L_\mathrm{bol}\sim0.2L_\odot$) and mass (M$*\sim$,0.15~M$\odot$) Class0 protostar IRAS 16253$-$2429, conducted as part of the \textit{eDisk} ALMA large program and the JWST cycle-1 GO program \textit{IPA}. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at $\leq$5$μ$m), with a brighter, extended northern side. We detect 15 pure rotational H$2$ transitions (E$\mathrm{up}$:1015–21411K), revealing a wide-angle molecular outflow. {The outflow width (as traced in H$_2$0-0S(11)) at the protostellar location measures $\leq$35 au, slightly larger than the dust and Keplerian disk diameters ($\sim$30 au) but wider than the 20–23au jet width in [Fe II].} {The opening angle narrows from 40–35\arcdeg{} for the low-J H$_2$ lines (up to S(5)) and the cold gas component (ALMA $^{12}$CO) to $\sim$28–19\arcdeg{} for the high-J H$_2$ lines (S(7)–S(11)).} Position-velocity diagrams of H$2$ reveal higher velocities for higher E${up}$, ranging from 12.5 kms$^{-1}$ for H$_2$0-0S(1) and S(2) to 28.5 kms$^{-1}$ for H$_2$0-0S(5)andS(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 mm CO may be gas from the infalling envelope accelerated outwards by the wide angle wind along the cavity walls.

💡 Research Summary

This paper presents a comprehensive study of the Class 0 protostar IRAS 16253‑2429, a very low‑luminosity (L_bol ≈ 0.2 L⊙) and low‑mass (M_* ≈ 0.15 M⊙) object, using a synergistic combination of JWST and ALMA observations. The JWST program (IP A, Cycle 1 GO) provided integral‑field spectroscopy from 2.9 to 28 µm with the NIRSpec IFU (F290LP/G395M) and the MIRI Medium‑Resolution Spectrograph (MRS) covering the inner 5.7″–14.6″ at spatial resolutions of 0.2″–1″ (≈28–140 au). ALMA eDisk data delivered ¹²CO J = 2‑1 line cubes at 0.07″ (≈9.8 au) resolution, enabling a detailed view of the gas kinematics.

The JWST images reveal a wide hourglass‑shaped cavity in scattered light, brighter toward the north, consistent with previous Spitzer IRAC maps. Fifteen pure rotational H₂ lines (0‑0 S(0)–S(11), E_up = 1015–21411 K) are detected, providing an unprecedented view of the molecular outflow. The low‑J lines (up to S(5)) and the ¹²CO emission trace a broad component with an opening angle of 40°–35°, while the high‑J lines (S(7)–S(11)) are confined to a narrower cone of 28°–19°. The H₂ 0‑0 S(11) line measures the outflow width at the protostellar position to be ≤35 au, slightly larger than the dust and Keplerian disk diameters (≈30 au) but broader than the 20–23 au jet seen in