The H₂ jet and disk wind of the Class I protostar HOPS 315

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

^★ Corresponding author; stijnvleugels@gmail.com

Received: 3 October 2024
Accepted: 19 February 2025

Abstract

Context. Protostellar outflows are important to many areas of star formation. They enable protostars to build mass by removing angular momentum from accreting material, mix hot solids into the comet-forming regions of young disks, and they provide chemical feedback to star-forming molecular clouds. However, the launching mechanisms of protostellar outflows at early ages are still debated. HOPS 315, a young Class I protostar known to exhibit a purely molecular H₂ jet, provides an interesting case to constrain launching models.

Aims. We aim to investigate the physical structure, kinematics, and spatial distribution of the outflowing material of HOPS 315 to constrain its components and their launching mechanism.

Methods. We analyse spatially resolved JWST MIRI and NIRSpec spectra of HOPS 315 and perform Gaussian fits to rotational and ro-vibrational H₂ emission lines. By constructing rotation diagrams in each spaxel, we map the morphology, velocity, temperature, and ortho-to-para ratio (OPR) in the outflow.

Results. We find that the mid-infrared 0–0 S(1)–S(5) rotational H₂ emission traces a wide-angle wind component, which peaks along the jet axis, while near-infrared ro-vibrational H₂ emission traces the collimated jet. The wind exhibits velocities ≳20 km s⁻¹, temperatures of 500–600 K, and an OPR of 3. We estimate a terminal velocity of 120–125 km s⁻¹ for the jet and a temperature of 2400–3800 K. The OPR in the jet decreases from 3 near the protostar to 2.49_−0.03^0.03 by 500 au from the protostar.

Conclusions. Our observations may be explained by an magneto-hydrodynamic (MHD) disk wind, wide-angled wind-driven outflows, or jet bow shock-driven outflows. The ortho-to-para disequilibrium in the jet possibly results from grain surface ortho-to-para conversion reactions in the inner disk. The presence of disk winds at this age is potentially consistent with theories of radial transport of hot material to the comet-forming regions of the Solar System.