EPISODE III: The Nested Jet/Outflow Morphology of EC 53 Revealed by JWST and ALMA

We present an extensive study of the structure and kinematics of the jet and outflow of EC 53, a Class I protostar with a quasi-periodic variability, using combined James Webb Space Telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations. ALMA continuum observations resolve a compact disk with a radius of $\sim$0.14\arcsec\ (60,au). Scattered light from the outflow cavity is prominent in the short-wavelength NIRCam and NIRSpec observations, revealing only the southeast nearside lobe. We detected 27 H$_2$ emission lines tracing a narrow, cone-shaped structure within the outflow cavity. A high-velocity ionized jet is detected in several forbidden atomic lines, characterized by a position angle of 142\degree, an opening angle of 1.4\degree, and an estimated geometric launching radius of at most $\sim$40,au. Mid-infrared CO ro-vibrational emission lines, stronger in the P-branch, show a similar distribution to the H$_2$ emission and are likely to originate from hot gas within the outflow cavity. CO and C$_2$H emission lines detected by ALMA trace slower, colder outflow components and cavity walls. The spatial and kinematic stratification between the hot atomic and molecular components and the colder molecular gas is consistent with predictions from MHD disk wind models, although envelope material entrained by a wide-angle wind or jet may also contribute. Our analysis highlights the powerful synergy between JWST and ALMA in advancing the understanding of protostellar jets and outflows across multiple spatial and physical scales.

💡 Research Summary

This paper presents a comprehensive, multi‑wavelength investigation of the jet and outflow system associated with the Class I protostar EC 53 (V371 Ser) in the Serpens Main star‑forming region, using coordinated observations from the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA). The authors combine high‑resolution ALMA continuum and line data (CO J=2–1, C₂H N=4–3) with JWST NIRCam imaging, NIRSpec integral‑field spectroscopy, and MIRI medium‑resolution spectroscopy to trace the physical conditions from the innermost disk (∼9 au) out to the extended outflow cavity (several thousand au).

The ALMA continuum resolves a compact, nearly circular disk of radius ≈0.14″ (∼60 au). Modeling of the visibilities yields a central mass of at least 0.3 M⊙ and an inclination of 34.8° ± 2°. The CO 2–1 line, observed with baselines ranging from 27 m to 15 km, reveals a high‑velocity component (±300 km s⁻¹) confined to a narrow, collimated jet and a low‑velocity, wide‑angle component (≤ 30 km s⁻¹) that delineates the cavity walls. The high‑velocity jet has a position angle of 142° and an opening angle of only 1.4°, implying a highly collimated flow launched from within ≲ 40 au of the star.

JWST NIRCam images show scattered light from the southeast (blueshifted) cavity at short wavelengths (1.7 µm), while longer wavelengths (≥ 4 µm) are dominated by the central point source because dust scattering efficiency drops. The NIRSpec IFU and MIRI MRS spectra detect 27 ro‑vibrational H₂ lines and a suite of forbidden atomic lines (