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arxiv: 2604.13773 · v1 · submitted 2026-04-15 · 🌌 astro-ph.SR · astro-ph.EP· astro-ph.GA

JOYS+: A JWST/MIRI survey of the evolution of H₂ winds and jets from low-mass protostars

L. Francis , {\L}. Tychoniec , E. F. van Dishoeck , A. D. Sellek , A.Caratti o Garatti , V. J. M. Le Gouellec , C. Gieser , H. Beuther
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J. M. Vorster M. E. Ressler P. Nazari B. Tabone K. Assani R. Devaraj J. J. Tobin Maria Gabriela Navarro P. C. Cort\'es J. M. Girart M. G\"udel Th. Henning G. \"Ostlin G. Wright T. Ray
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Pith reviewed 2026-05-10 12:19 UTC · model grok-4.3

classification 🌌 astro-ph.SR astro-ph.EPastro-ph.GA
keywords protostellar outflowsH2 windsJWST MIRIClass 0 protostarsClass I protostarsmass-loss ratesMHD disk winds
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The pith

H2 mass-loss rates in protostellar outflows drop by two orders of magnitude from Class 0 to Class I while wind opening angles widen from 20 to 90 degrees.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

JWST MIRI/MRS observations of 33 Class 0 and I protostars map the H2 S(1) and S(7) lines to trace molecular winds and jets. Low-J lines reveal extended low-velocity wide-angle winds that overlap with sub-mm CO emission from ALMA, while high-J lines mark shocks and knots along the axis in Class 0 sources. Rotation diagrams show a dominant warm 600 K component whose mass-loss rates, derived from line velocity and outflow width, fall by a factor of 100 from Class 0 to Class I and correlate with bolometric luminosity. Opening angles broaden and high-velocity H2 jets disappear in the Class I stage. These patterns match the evolutionary predictions of MHD disk wind models.

Core claim

The survey finds that warm H2 outflows carry most of the molecular mass at ~600 K and exhibit declining mass-loss rates by two orders of magnitude, increasing opening angles from ~20° to ~90°, and loss of collimated jets between Class 0 and Class I stages, all consistent with magnetocentrifugal disk wind launching as accretion rates drop.

What carries the argument

H2 S(1) and S(7) line flux and velocity maps combined with rotation-diagram fits to separate warm and hot temperature components, then scaled by outflow width and velocity to compute mass-loss rates.

Load-bearing premise

The H2 S(1) and S(7) lines plus rotation diagrams accurately trace the bulk molecular outflow mass and velocity structure without large corrections from optical depth or non-LTE effects.

What would settle it

Detection of persistent high-velocity H2 jets or flat mass-loss rates across Class 0 to I sources in deeper or multi-transition data would contradict the claimed evolutionary decline.

Figures

Figures reproduced from arXiv: 2604.13773 by A.Caratti o Garatti, A. D. Sellek, B. Tabone, C. Gieser, E. F. van Dishoeck, G. \"Ostlin, G. Wright, H. Beuther, J. J. Tobin, J. M. Girart, J. M. Vorster, K. Assani, L. Francis, {\L}. Tychoniec, Maria Gabriela Navarro, M. E. Ressler, M. G\"udel, P. C. Cort\'es, P. Nazari, R. Devaraj, Th. Henning, T. Ray, V. J. M. Le Gouellec.

Figure 1
Figure 1. Figure 1: Continuum subtracted line maps of our sample ordered by bolometric temperature. First and fourth rows: CO 3-2 or 2-1 emission integrated from ±30 km s−1 of the source velocity. Second and fifth rows: integrated H2 S(1) line emission. Third and sixth rows: integrated H2 S(7) emission. The location of the sub-mm peak tracing the protostar driving the outflow is marked by a white star, while the centre of the… view at source ↗
Figure 2
Figure 2. Figure 2: As [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Continuum subtracted line centroid and moment 1 maps of our sample ordered by bolometric temperature, annotated as described in [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: As [PITH_FULL_IMAGE:figures/full_fig_p008_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Example of outflow angle measurement from the H2 S(1) line for the case of BHR-71 IRS 2 (see text). 3.5. H2 mass loss rates For each blue-shifted outflow lobe, we infer the H2 mass loss rate following the method of Delabrosse et al. (2024) used for the DG Tau B disk wind: M˙ = 2mH NH2Lperpvperp (1) where NH2 is the average H2 column density in an aperture within a given position in the outflow derived from… view at source ↗
Figure 6
Figure 6. Figure 6: Measured opening angle in the H2 S(1) emission for our sam￾ple vs bolometric temperature (top panel) and envelope mass (bottom panel). Symbols for Class 0 sources are filled diamonds, while class I sources are open diamonds. We calculate the outflow rate for the warm component in all cases, and for the hot component where there are sufficient high￾Article number, page 8 of 18 [PITH_FULL_IMAGE:figures/full… view at source ↗
Figure 7
Figure 7. Figure 7: Variation of warm H2 outflow properties with deprojected dis￾tance from the protostar. The outflow width (third panel) is determined from the H2 S(1) line map (Figures 1-2). The velocity error bars do not include the systematic error associated with inclination correction. 4. Discussion 4.1. Outflow property evolution - H2 temperature, mass, and velocity To examine trends in the H2 emission properties and … view at source ↗
Figure 8
Figure 8. Figure 8: Best-fit excitation temperature of the warm (red circles) and hot (blue triangles) components versus bolometric temperature towards each aperture used for outflow mass-loss measurement in our sample. The shaded regions indicate the average uncertainty on each quantity. The Tbol = 70 K boundary between Class 0 and I sources is indicated by the dashed line, and Class I sources are plotted as open symbols. In… view at source ↗
Figure 9
Figure 9. Figure 9: Mass loss rate in the warm H2 component towards the outflows in our sample versus bolometric temperature and luminosity. The bolo￾metric luminosity is also converted to an estimate of the mass accretion rate (see text), though we note that this may overestimate the accretion rate if the contribution from the stellar photosphere is relatively high (Hartmann et al. 2025). Solid, dashed, and dotted lines show… view at source ↗
Figure 10
Figure 10. Figure 10: Mass loss rate and force of the warm H2 component versus low-J CO towards the outflows in our sample. The large difference in warm H2 and cold CO mass-loss rate and momentum flux could be explained the presence of an ad￾ditional cold H2 component of the wind corresponding to the cold CO traced in the sub-mm. This is motivated by the simi￾larity in morphology of the warm H2 wind and the sub-mm CO Article n… view at source ↗
read the original abstract

Protostellar outflows display wide-angle winds and collimated jets, the magnetocentrifugal launching of which enables accretion onto the protostar. The majority of the outflow mass is likely ejected or entrained molecular H$_2$, which can now be studied in unprecedented detail with JWST. Using JWST MIRI/MRS observations towards 13 single and 20 multiple Class 0 and I protostars, we investigate the nature and evolution of the H$_2$ wind and jet morphology, mass outflow rate, and velocity and temperature structure. We construct line flux and velocity maps of the H$_2$ S(1) and S(7) lines as well as the sub-mm CO traced by ALMA. Low-$J$ ($J\le4$) H$_2$ transitions trace extended wide-angle, low-velocity (0-20 km s$^{-1}$) winds within the contours of the low-velocity ($< 30$ km s$^{-1}$) sub-mm CO emission, while high-$J$ ($J >5$) transitions are associated with shocks and knots. In Class 0 sources with a known high-velocity ($> 30$ km s$^{-1}$) molecular CO or SiO jet, higher H$_2$ velocities are found along the jet axis. The opening angle of the wind traced by the H$_2$ S(1) line broadens from $\sim20^\circ$ to $\sim90^\circ$ through the Class 0 to Class I stage. Near the base of each blue-shifted outflow lobe, we extract representative spectra, where rotation diagram fitting of the H$_2$ lines is combined with the outflow width and H$_2$ line velocity to measure the mass-loss rates. The rotation diagrams show a warm $\sim 600$ K, component with two orders of magnitude more mass than the hot, 1500-3000 K component. The H$_2$ outflow mass-loss rates decline by two orders of magnitude from the Class 0 to Class II stage and are correlated with bolometric luminosity. The declining warm H$_2$ mass loss rates and increasing opening angles from the Class 0 to I stages, and the absence of H$_2$ jets in the Class I sources, are consistent with the predictions of MHD disk wind models.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript reports JWST/MIRI/MRS observations of H2 S(1) and S(7) emission toward 13 single and 20 multiple Class 0 and I low-mass protostars. Low-J H2 lines trace extended wide-angle (increasing from ~20° to ~90°), low-velocity (0-20 km s^{-1}) winds aligned with sub-mm CO, while high-J lines trace shocks and knots. In sources with known high-velocity jets, higher H2 velocities align with the jet axis. Rotation diagrams near the base of blue-shifted lobes yield a dominant warm (~600 K) component with two orders of magnitude more mass than the hot (1500-3000 K) component; combining these with outflow width and velocity gives H2 mass-loss rates that decline by two orders of magnitude from Class 0 to Class I (and are correlated with bolometric luminosity), with no H2 jets detected in Class I sources. These trends are stated to be consistent with MHD disk-wind model predictions.

Significance. If the reported trends are robust, the work supplies a statistically useful observational benchmark for the evolutionary transition from collimated jets to wide-angle winds and the corresponding drop in warm molecular mass ejection, directly testing magnetocentrifugal launching scenarios. The separation of warm and hot H2 components via rotation diagrams, the spatial comparison with ALMA CO, and the luminosity correlation add quantitative value. The use of public JWST data and standard analysis techniques supports reproducibility and positions the survey as a reference for future studies of accretion-ejection coupling.

minor comments (3)
  1. [Methods (mass-loss rate derivation)] The abstract states that rotation-diagram fitting is combined with outflow width and line velocity to derive mass-loss rates; a short methods subsection or appendix equation showing the exact formula (e.g., how width is measured from the S(1) map and how it enters the rate) would improve clarity and allow direct reproduction.
  2. [Sample description] The sample includes both single and multiple systems; a brief statement or supplementary table indicating whether the reported opening-angle and mass-loss trends remain unchanged when restricted to the 13 single sources would strengthen the evolutionary interpretation.
  3. [Results (velocity and morphology maps)] Figure captions and text refer to velocity ranges (0-20 km s^{-1} for winds, >30 km s^{-1} for jets) without a summary table listing measured velocities or opening angles per source; adding such a table would aid readers in assessing the scatter around the reported Class 0-to-I trends.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive and constructive review. Their summary accurately captures the key findings of our JWST/MIRI survey on the evolution of H2 winds and jets, and we appreciate the recognition of the statistical value of the trends, the rotation-diagram analysis, and the comparison with MHD disk-wind models. We are pleased that the referee recommends acceptance.

Circularity Check

0 steps flagged

No significant circularity

full rationale

This is a purely observational survey paper. Mass-loss rates are computed from measured line fluxes via standard rotation diagrams (temperature and column density) combined with observed spatial widths and velocities; these are direct data products, not internal predictions that reduce to fitted parameters by the paper's own equations. Evolutionary trends (declining rates, increasing opening angles, absence of jets in Class I) are reported from the sample without self-referential derivation. Model comparisons invoke external MHD disk-wind predictions and are not load-bearing for the observational results. No self-citations function as uniqueness theorems or ansatzes that close the central claims. The derivation chain is self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claims rest on standard spectroscopic assumptions for interpreting H2 line emission as outflow tracers; no new entities are postulated.

free parameters (1)
  • rotation diagram fit parameters
    Temperatures and column densities derived from H2 line ratios; values fitted per source.
axioms (1)
  • domain assumption H2 emission traces the dominant molecular component of the outflow mass
    Invoked when converting line fluxes to mass-loss rates via width and velocity.

pith-pipeline@v0.9.0 · 5888 in / 1278 out tokens · 51965 ms · 2026-05-10T12:19:28.093332+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. JOYS: Launching and destruction of dust in protostellar jets. The case of BHR71-IRS1 with JWST/MIRI

    astro-ph.SR 2026-04 conditional novelty 7.0

    JWST data shows dust grains are launched in a Class 0 jet and at least partly survive shock processing, with measurable refractory depletion in the gas.

Reference graph

Works this paper leans on

4 extracted references · 4 canonical work pages · cited by 1 Pith paper · 1 internal anchor

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    The reduction for most sources are de- scribed in the provided references, with two exceptions

    Appendix B: ALMA data The details of the ALMA CO data collected for our sample are given in Table B.1. The reduction for most sources are de- scribed in the provided references, with two exceptions. Data from the ALPPS program (2021.1.00418.S, PI: C. Hull) were reduced following the same procedure as described in (Cortés et al

    work page 2021

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    Data for NGC 1333 IRAS 2A, B1-c, L1448-mm, and IC348-MMS were taken from 2021.1.01578.S Fig

    for SVS 13A. Data for NGC 1333 IRAS 2A, B1-c, L1448-mm, and IC348-MMS were taken from 2021.1.01578.S Fig. C.1.Example of rotation diagram fitting in the Ser-SMM3 outflow. The aperture shown is marked by a red cross in Figures 1 and

    work page 2021

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    The best fit to the warm and hot components are show as dotted and dashed lines respectively, while the solid line indicates the best overall fit

    The observed data points and the data after correction for extinction and a non-LTE ortho-to-para ratio are indicated by the red and blue points respectively. The best fit to the warm and hot components are show as dotted and dashed lines respectively, while the solid line indicates the best overall fit. (PI: B. Tabone) and reduced following the same proc...

    work page 2024