# The nested morphology of disk winds from young stars revealed by JWST/NIRSpec observations

Ilaria Pascucci, Tracy L. Beck, Sylvie Cabrit, Naman S. Bajaj, Suzan

Edwards, Fabien Louvet, Joan R. Najita, Bennett N. Skinner, Uma Gorti, Colette Salyk, et al.

► To cite this version:

Ilaria Pascucci, Tracy L. Beck, Sylvie Cabrit, Naman S. Bajaj, Suzan Edwards, et al. The nested morphology of disk winds from young stars revealed by JWST/NIRSpec observations. Nature Astronomy, 2025, pp.81-89. 10.1038/s41550-024-02385-7. insu-04822425

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# The nested morphology of disk winds from young stars revealed by JWST/NIRSpec observations

Received: 27 February 2024

Accepted: 10 September 2024

Published online: 4 October 2024

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Ilaria Pascucci<sup>1, ∗</sup>, Tracy L. Beck<sup>2</sup>, Sylvie Cabrit<sup>1,3,4</sup>, Naman S. Bajaj<sup>1</sup>,
Suzan Edwards<sup>5</sup>, Fabien Louvet<sup>1,4</sup>, Joan R. Najita<sup>6</sup>, Bennett N. Skinner<sup>1,7</sup>,
Uma Gorti<sup>1,8,9</sup>, Colette Salyk<sup>10</sup>, Sean D. Brittain<sup>11</sup>, Sebastiaan Krijt<sup>1,12</sup>,
James Muzerolle Page<sup>1,2</sup>, Maxime Ruaud<sup>1,8</sup>, Kamber Schwarz<sup>1,13</sup>,
Dmitry Semenov<sup>1,13,14</sup>, Gaspard Duchêne<sup>1,4,15</sup> & Marion Villenave<sup>16</sup>

Radially extended disk winds could be the key to unlocking how protoplanetary disks accrete and how planets form and migrate. A distinctive characteristic is their nested morphology of velocity and chemistry. Here we report James Webb Space Telescope near-infrared spectrograph spectro-imaging of four young stars with edge-on disks, three of which have already dispersed their natal envelopes. For each source, a fast collimated jet traced by [Fe II] is nested inside a hollow cavity within wider lower-velocity H₂. In one case, a hollow structure is also seen in CO ro-vibrational (ν = 1 → 0) emission but with a wider opening angle than the H₂, and both of those are nested inside an Atacama Large Millimeter Array CO (J = 2 → 1) cone with an even wider opening angle. This nested morphology, even for sources with no envelope, strongly supports theoretical predictions for wind-driven accretion and underscores the need for theoretical work to assess the role of winds in the formation and evolution of planetary systems.

The assembly of stars and their planetary systems proceeds through an accretion disk, in which magneto-rotational instability<fnref n="1" /> was long favoured for transporting angular momentum outward to aid inward accretion. Recent simulations incorporating disk microphysics challenge this view and show that magneto-rotational instability is suppressed in most of the planet-forming region (~1–20 au). Instead, radially extended magnetohydrodynamic (MHD) disk winds—outflowing gas from a few scale heights above the disk midplane launched by magnetic and thermal pressures—emerge as a viable mechanism for

angular momentum removal and for enabling accretion (ref. 2 and references therein). This new wind-driven accretion scenario greatly impacts the evolution of the disk surface density³, thus affecting the inward drift of solids⁴ and where planets may form and migrate to<fnref n="5" />. Consequently, observations that can confirm the presence of these winds are crucial.

A unique feature of radially extended MHD winds is that flows are launched over a broad range of disk radii, hence outflow velocities, from near the gas co-rotation radius (-0.1 au) and across much

<footnote n="1">¹Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ, USA. ²Instruments Division, Space Telescope Science Institute, Baltimore, MD, USA. ³Observatoire de Paris - PSL University, Sorbonne Université, LERMA, CNRS, Paris, France. ⁴Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France.</footnote>

<footnote n="5">⁵Five College Astronomy Department, Smith College, Northampton, MA, USA. ⁶NSF, NOIRLab, Tucson, AZ, USA. ⁷Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada. ⁸Carl Sagan Center, SETI Institute, Mountain View, CA, USA. ⁹Ames Research Center, NASA, Moffett Field, CA, USA. ¹⁰Department of Physics and Astronomy, Vassar College, Poughkeepsie, NY, USA. ¹¹Department of Physics and Astronomy, Clemson University, Clemson, SC, USA. ¹²Department of Physics and Astronomy, University of Exeter, Exeter, UK. ¹³Max-Planck-Institut für Astronomie, Heidelberg, Germany. ¹⁴Department of Chemistry, Ludwig-Maximilians-Universität, Munich, NY, Germany. ¹⁵Department of Astronomy, University of California, Berkeley, CA, USA. ¹⁶Dipartimento di Fisica, Università degli Studi di Milano, Milan, Italy. e-mail: pascucci@arizona.edu</footnote>
<table><caption>Table 1 | Source properties from the literature relevant to this study</caption><thead><tr><th>Source</th><th>Right ascension (J2000)<br>(hmins)</th><th>Declination (J2000)<br>(M<sub>☉</sub>)</th><th>M.</th><th>F<sub>mm</sub><br>(mJy)</th><th>PA<sub>mm</sub><br>(°)</th><th>i<sub>mm</sub><br>(°)</th><th>R<sub>mm</sub><br>(au)</th><th>R<sub>lr</sub><br>(au)</th><th>Refs.</th></tr></thead><tbody><tr><td>FS Tau B</td><td>42200.7</td><td>+26°57′32.5"</td><td>0.7</td><td>341</td><td>145</td><td>74</td><td>144</td><td>161</td><td>21,59</td></tr><tr><td>HH 30</td><td>43137.5</td><td>+18°12′24.5"</td><td>0.5</td><td>55</td><td>121</td><td>>85</td><td>130</td><td>217</td><td>21,38</td></tr><tr><td>IRAS 04302</td><td>43316.5</td><td>+22°53′20.4"</td><td>1.3–1.7</td><td>268</td><td>175</td><td>>84</td><td>220</td><td></td><td>21,59</td></tr><tr><td>Tau 042021</td><td>42021.4</td><td>+28°13′49.2"</td><td>0.4</td><td>124</td><td>-16</td><td>>85</td><td>287</td><td>350</td><td>21,60</td></tr></tbody></table>

M. was inferred from the Keplerian rotation of the disk gas, observed through well-resolved millimetric-wavelength spectro-imaging of molecular lines. $F_{mm}$, $PA_{mm}$, $i_{mm}$, and $R_{mm}$ are the flux density, position angle, inclination and disk radius from spatially resolved ALMA band 7 (0.89 mm) continuum images, which trace millimetre-sized grains. $R_{lr}$ is the disk radius from optical/ near-infrared scattered light images, thus probing small submicrometre grains coupled well with the gas.

of the planet-forming region (for example, ref. 6). This contrasts with X-winds, in which stellar field lines couple narrowly to the disk at the co-rotation radius and launch fast MHD winds (-150 km s⁻¹) that spread widely⁷ and photoevaporative winds, which develop only where the disk gas has enough thermal energy to escape the stellar gravitational field, namely beyond ~1 au and with speeds ≤10 km s⁻¹ (ref. 8). Another distinctive characteristic of radially extended MHD winds is their nested morphology of velocity and chemistry throughout all stages of star-disk evolution. A fast ~100 km s⁻¹ jet, formed by the recollimation of the inner wind, lies inside atomic and molecular gas moving at sequentially lower velocities (for example, ref. 9). X-winds can also collimate a jet (for example, ref. 10). However, lower-velocity flows arise solely from material entrained by the fast wind, which sweeps up gas near the disk surface¹¹ and, when an infalling envelope is present, also gathers envelope material near the disk's outer edge¹². Conversely, in the photoevaporative scenario, the absence of recollimation means fast jets are not produced and the wind's opening angle remains close to that at launch (for example, ref. 13).

Current kinematic data on young stars (-0.1–10 Myr) with a mass greater than that of the infalling envelope—class I and II sources¹⁴—hint at the presence of radially extended MHD winds. Spatially unresolved spectra of optical forbidden emission, like [O I] and near-infrared emission of H₂, can show, in addition to a high-velocity component (-50–300 km s⁻¹) tracing the base of a jet, a second lower-velocity component with broad linewidths, which is interpreted as originating over disk radii ~0.5–5 au (for example, ref. 15). A handful of spatially resolved outflows point to velocities that decrease outwards, with the narrow fast jet along the axis of a wider-angle lower-velocity flow (ref. 16 and references therein). However, the limited number of spatially resolved flows, especially for sources that have dispersed their natal envelopes (for example, refs. 17–19), has thus far hindered a detailed mapping of the wind morphology across chemical species, leaving the predicted nested structure by radially extended MHD winds uncertain.

## Results

We used the near-infrared spectrograph (NIRSpec) on the James Webb Space Telescope (JWST)²⁰ to acquire deep spectro-imaging of four edge-on disks with known jets (for example, ref. 21). All sources belong to the nearby (-140 pc) and young (-1–2 Myr) Taurus star-forming region (for example, ref. 22). See Table 1 for their properties relevant to this study. Although infrared spectral indices are often used to assign classes to young stellar systems as proxies for their evolutionary stage (for example, ref. 23), this method is unreliable for edge-on disks²⁴. Comparing the millimetre disk fluxes recorded by the Atacama Large Millimeter Array (ALMA; Table 1) with single-dish fluxes²⁵⁻²⁸ revealed that only IRAS 04302 is surrounded by an envelope. The other sources' fluxes are primarily from disk emission, which suggests that they are at a more evolved evolutionary stage with no notable infalling envelope that aligns with the class II category.

The integral field unit (IFU) of NIRSpec covers a field of view of ~3" × 3" with a pixel scale of 0.1" and, with our use of the three high-resolution gratings, delivers 0.95–5.27 µm spectra at each pixel with a velocity sampling of ~40 km s⁻¹ (see Methods for details on the observations and data reduction). Several [Fe II], H and H₂ lines were detected in the integrated spectra along with the P- and R-branches of the CO (ν = 1 → 0) ro-vibrational transition at ~4.7 µm (some of the detected lines are highlighted in Fig. 1). We focused on the brightest [Fe II] line at 1.644 µm, a known jet tracer (for example, ref. 29), the H₂ 0 → 0 S(9) line at 4.695 µm, and the CO (ν = 1 → 0) band. We selected the H₂ S(9) line, the brightest long-wavelength transition in our sample, due to its considerably lower scattering from the disk surface relative to shorter-wavelength H₂ lines, like the often-studied 2.12 µm 1 → 0 S(1) line. Its integrated flux is at most half that of the S(1) line (Table 2 and Methods). Thus, it combines the advantages of tracing the H₂ morphology closer to the disk with considerable relative brightness. The similarity of the [Fe II] fluxes in our sample (Table 2) hints at similar jet mass-loss rates. Considering the estimate for HH 30 of 2 × 10⁻⁹ M☉ yr⁻¹ (ref. 30) and factoring in the typical jet/accretion ratio of approximately 0.1 (ref. 31), it is probable that our sources are accreting at rates exceeding 10⁻⁸ M☉ yr⁻¹. This inference is supported by the sole mass accretion rate available in the literature for our sample, that for FS Tau B, which is ~1.5 × 10⁻⁷ M☉ yr⁻¹ (ref. 32).

Figure 2 shows continuum-subtracted line maps after the point spread function (PSF) deconvolution of the 1.644 µm [Fe II] line, the H₂ 0 → 0 S(9) line, along with the sum of the CO P-branch lines between ~4.7 and 4.9 µm (see Methods for details). The continuum emission below the H₂ S(9) line, which traces light scattered by small grains at the disk surface, is also displayed in one panel in each row. The main panels show three-colour composite images combining the [Fe II] and H₂ lines with the continuum emission. Additionally, integrated CO P-branch contours are overlaid in grey. [Fe II] traces the narrow jet emission, and we verified that its position angle (PA) was perpendicular to the ALMA millimetre disk (Tables 1 and 2). We also generated H₂ maps for the 1 → 0 S(1) at 2.12 µm and the 0 → 0 S(8) at 5.05 µm lines and found similar morphologies to the H₂ 0 → 0 S(9) line, which is, thus, representative for the molecular hydrogen gas. In addition, we created velocity centroid maps for the [Fe II] and H₂ lines and found that the NIRSpec resolution can discern small shifts between the blue lobe and red lobe of the [Fe II] jets (Methods). The images in Fig. 2 have been rotated to align the blueshifted jet emission vertically at the top of each panel. The H₂ maps show no resolved velocity structure, as expected if the molecular gas is moving more slowly than the jet.

For each source, the narrow [Fe II] jet is nested within wider H₂ emission, which is always more vertically extended than the continuum emission at the same wavelength. Although the overall [Fe II]/H₂ morphology, with a narrow atomic jet along the axis of a wider H₂ cone, has been seen in a few other sources (for example, refs. 17, 33, 34), we identify the presence of a central cavity in the H₂ cone. Emission in a cone with a hollow centre, in the absence of ambient material, is expected if
<figure><img src="image_3.png" /><figcaption>**Fig. 1 | Spectra integrated over the NIRSpec IFU.** Semitransparent regions indicate the minimum and maximum wavelength cutoffs of the detectors' gaps. The H₂O, CO₂ and CO ice bands are identified with grey arrows. A few of the strongest emission lines are marked with grey dotted lines. All these lines are spatially extended. The transitions analysed in this study are highlighted in bold.</figcaption></figure>

<table><caption>**Table 2 | Inferred jet and wind properties**</caption><thead><tr><th rowspan="3">Source</th><th colspan="3">Jet: [Fe II] 1.644 µm</th><th colspan="3">Wind: H<sub>2</sub> 0→0 S(9) 4.695 µm</th></tr><tr><th>Flux</th><th>PA</th><th>θ<sub>j</sub></th><th>Flux</th><th>θ<sub>w</sub></th><th>R<sub>geo</sub></th></tr><tr><th>(ergs<sup>-1</sup>cm<sup>-2</sup>)</th><th>(°)</th><th>(°)</th><th>(ergs<sup>-1</sup>cm<sup>-2</sup>)</th><th>(°)</th><th>(")</th></tr></thead><tbody><tr><td>FS Tau B</td><td>4.1×10<sup>-15</sup></td><td>55±3</td><td>16.8±2.5</td><td>3.5×10<sup>-15</sup></td><td>41.2±7.9</td><td>-0.05±0.15</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>50.3±2.3</td><td>-0.03±0.05</td></tr><tr><td>HH 30</td><td>2.0×10<sup>-15</sup></td><td>32±2</td><td>2.6±0.5</td><td>1.5×10<sup>-15</sup></td><td>14.1±0.5</td><td>-0.04±0.01</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>12.8±0.5</td><td>0.05±0.01</td></tr><tr><td>IRAS 04302</td><td>3.0×10<sup>-15</sup></td><td>87±2</td><td>7.5±0.9</td><td>4.0×10<sup>-15</sup></td><td>38.7±3.8</td><td>-0.04±0.09</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>27.8±1.8</td><td>0.04±0.03</td></tr><tr><td>Tau 042021</td><td>3.2×10<sup>-15</sup></td><td>72±2</td><td>5.3±1.0</td><td>4.5×10<sup>-16</sup></td><td>38.5±4.5</td><td>-0.02±0.08</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>37.6±2.6</td><td>0.04±0.05</td></tr></tbody></table>

The [Fe II] and H₂ lines we have selected are among the most prominent tracers of jets and winds, respectively. For each source, we list the jet's semi-opening angle ($\theta_j$) and the wind's semi-opening angle ($\theta_w$) and extrapolated radius at $z=0$ ($R_{geo}$) for both lobes of the blueshifted emission. The quoted uncertainties on these values are one standard deviation. FS Tau B's disk is less inclined than the others. Hence, the disk plane and $R_{geo}$ are less well determined (Methods). The uncertainty in the integrated line fluxes is dominated by the 10% absolute photometric accuracy of the NIRSpec spectra (Methods)³⁰.

H₂ traces material lifted from the disk, that is a disk wind that emerges at a larger radial distance than the jet (for example, ref. 9). Extended CO ro-vibrational emission is detected for three of the sources. Uniquely for HH 30, this emission mirrors the H₂ conical morphology, albeit less vertically extended, with a central cavity surrounding the jet. This represents the resolved mapping of a wind-like structure in the CO ($\nu = 1 \to 0$) band (see ref. 35 and references therein for hints of winds in this tracer through spectro-astrometry).

A notable brightness asymmetry relative to the disk plane is seen in the jet and wind features for two of our sources, FS Tau B and HH 30. In both cases, the more prominent emission is on the side of the disk where the jet is blueshifted. Although this asymmetry was already known for their jets³⁶,³⁷, it has now been seen in the winds as well. This discovery is particularly noteworthy for FS Tau B, marking the first such observation in its wind. For HH 30, our finding corroborates the asymmetry previously noted in the millimetre CO ($\nu = 2 \to 1$) wind emission³⁸.

For each source, we traced the [Fe II] jet and H₂ wind emission to quantify their semi-opening angles ($\theta_j$ and $\theta_w$) and estimate the radii where the wind intersects the disk plane (geometric radii, $R_{geo}$). See Methods for details and Table 2 for the results. The jet semi-opening angles vary between -2.5° and -17°, consistently smaller than their corresponding wind semi-opening angles, which range from -13° to 50°. HH 30 stands out as having the most collimated jet and the narrowest wind among our sources (Fig. 3), although similarly narrow jets have been reported in other class II sources (for example, ref. 39). The wind semi-opening angle that we estimate for Tau 042021 is the same as that recently reported in ref. 19 using a lower spatial resolution H₂ S(2) map obtained with the mid-infrared instrument (MIRI) onboard JWST. Our PSF-deconvolved images enable us to measure the semi-opening angle of its jet, which was unresolved with MIRI. In addition, we can place stringent constraints on the intersection points of the H₂ cones with the disk plane. Specifically, we determine that these intersections
<figure><img src="image_4.png" /><figcaption>**Fig. 2 | Composite NIRSpec images.** [Fe II] emission at 1.644 µm in blue, H₂ 0 → 0 S(9) emission at 4.695 µm in green and the continuum emission (Cont.) at the H₂ line in red. CO emission from -4.7–4.9 µm is shown in the right bottom panels of each row in grey. The 50% of the peak emission contour (and for HH 30 also the 30%) is shown in grey in each composite image. In every instance, the collimated jet traced by [Fe II] is nestled inside the wider H₂ emission and, for HH 30, also the CO ($v = 1 \rightarrow 0$) emission.</figcaption></figure>

occur at $R_{\text{geo}} < 0.1$" (Table 2; 14 au at the average distance of Taurus), well inside the disk outer radii of -150–350 au. If these cones trace MHD winds, the decreasing wind opening angle with height due to magnetic recollimation (for example, ref. 40) implies that each $R_{\text{geo}}$ defines an upper boundary for the actual wind-launching radius.

## Discussion and conclusions

Different types of disk winds, with distinct kinematic and morphological features, have been discussed in the literature review. X-winds have been invoked to spin down the accreting star<sup>7</sup>, whereas photoevaporative winds might drive disk dispersal<sup>8</sup>. Only radially extended MHD

winds could solve the long-standing puzzle of how protoplanetary disks accrete (see refs. 2,16, for recent reviews).

The edge-on orientations of our systems provide a unique advantage when mapping out the structure of their disk winds, as the bright flux of the central star is effectively masked by the disk. The NIRSpec IFU spectral imaging has revealed the morphology of the atomic and molecular disk wind components in striking detail for several class II systems, on spatial scales reaching down to 30 au from the disk plane. In all cases, a collimated jet traced by [Fe II] is encased within the wider-angle emission from H₂, and in one case, also CO ($v = 1 \rightarrow 0$). The near-infrared molecular emission extends well above 100 au from the disk plane with a characteristic conical shape previously noted in a few other systems (for example, refs. 17–19). The consistent detection of a pronounced central cavity, marked by a notable absence of emission at the H₂ axial position, is an important finding. Moreover, the molecular wind emission appears to be anchored at radial distances <15 au, well inside the disk radii. High-resolution ground-based spectroscopy of class I and II sources has found low-velocity H₂ 2.12 µm flows reaching blueshifted speeds of up to ~20 km s⁻¹ (for example, ref. 15). Although H₂ velocities were not measured for our edge-on sources ('Results'), similarly low velocities probably characterize the molecular structures that we have imaged.

For HH 30, we also compared the brightest component of the wind traced with NIRSpec in H₂ and CO ($v = 1 \rightarrow 0$) with that probed with ALMA in the CO ($J = 2 \rightarrow 1$) line, as shown in the left panel of Fig. 4. The CO millimetre emission traces gas flowing at ~10 km s⁻¹ and has a hollow cone shape but with a semi-opening angle of ~35° (ref. 38), considerably wider than the ~13° and ~18° semi-opening angles of the warmer H₂ and CO ($v = 1 \rightarrow 0$) cones (Table 2 and caption of Fig. 4). The latter nestle inside the millimetre cavity and, as expected, the average $R_{\text{geo}}$ derived from H₂ (-6 ± 2 au) falls below the ~10 au deduced from the CO ($J = 2 \rightarrow 1$) emission<sup>38</sup>. These distinctive nested hollow structures might be less discernible at lower disk inclinations. However, observations at lower inclinations provide complementary information, especially for the flow velocity, when performed with high-resolution spectroscopy.

Three of our systems appear to have dispersed most of their primordial envelopes ('Results'), as indicated by the similarity of the single-dish continuum millimetre fluxes and the ALMA disk fluxes. The absence of an envelope disfavours scenarios in which the observed wide-angle lower-velocity molecular flows trace infalling envelope material swept up and entrained by an X-wind or the jet itself<sup>41,42</sup>. Additionally, our $R_{\text{geo}}$ values are more than an order of magnitude smaller than the disk radii, which are the base of the X-wind swept-up shell<sup>43</sup>. The alternative of lower-velocity material entrained at the disk surface by a wide-angle X-wind<sup>11</sup> can also be excluded given the vertical extent and semi-opening angle ≤50° of the H₂ emission detected with NIRSpec. Thus, although jet production by the X-wind cannot be ruled out, its role in generating the observed molecular flows seems very unlikely.

Photoevaporative winds produce molecular flows only beyond several astronomical units and with velocities of just a few km s⁻¹ and opening angles of around 45° (for example, ref. 44). Photoevaporative winds struggle to account for H₂ flows exceeding 5 km s⁻¹ and cannot match the 100 au vertical extent seen in our NIRSpec data (see ref. 45 for the predicted H₂ 2.12 µm-emitting region). Moreover, the near-infrared H₂ and CO cones observed in HH 30 are narrower (Fig. 4) than those predicted by photoevaporative winds, and the mass flux derived from CO ALMA data exceeds typical photoevaporative mass-loss rates<sup>13,38,45</sup>. Importantly, photoevaporative winds do not recollimate to produce fast axial jets. Hence, they would need to be coupled with an MHD wind to reproduce the narrow [Fe II] emission seen in our sample. These inner winds might shield high-energy photons from the central star, diminishing their capacity to reach the outer disk and drive photoevaporative flows (Fig. 8 in ref. 16). The absence of [Ne II] 12.8 µm low-velocity flows from stars with accretion rates $\ge 10^{-8} M_{\odot} \text{yr}^{-1}$, akin to those of our
<figure><img src="image_5.png" /><figcaption>**Fig. 3** | Traces of the outer edges of the [Fe II] at 1.644 µm and H₂ S(9) emission. Left, FWHM of the jet's blueshifted component as a function of distance from the disk plane. Right, edges of the wind's blueshifted component versus the disk's plane. In both panels, filled symbols represent data points used in the linear fit to estimate the jet and the wind semi-opening angles and R<sub>geo</sub></figcaption></figure>

(Table 2). The best fits are shown with dashed lines. Data points near the disk plane are not included in the fit due to inadequate sampling of the FWHM and scattering (see Methods for details). For IRAS 04302, we excluded points above 1.2" as they clearly deviate from a wind-like morphology. HH 30 has the narrowest jet and wind in our sample.

<figure><img src="image_6.png" /><figcaption>**Fig. 4** | Emission structures of [Fe II], H₂ and CO in HH 30. Left, composite image of [Fe II] at 1.644 µm (blue), H₂ at 4.695 µm (green), ALMA CO (2 → 1) in the local standard of rest velocity 8.3 ± 0.3 km s⁻¹ (red) and after removing the disk emission³⁸. The NIRSpec CO (ν = 1 → 0) traces of the outer edges are shown in grey. Right, trace of the [Fe II] jet centroid (blue) and traces of the outer edges of the H₂ (green) and CO (ν = 1 → 0, grey) components detected with NIRSpec.</figcaption></figure>

The CO (ν = 1 → 0) semi-opening angle and geometric radius are 17.8° ± 2.5° and 0.075" ± 0.025" (10.5 ± 3.5 au), respectively. These are larger than those measured in H₂ (13.5° ± 1.1° and 0.045" ± 0.01"; see also Table 2). With the NIRSpec H₂ outer edge inside that of the CO (ν = 1 → 0) and both emissions enclosed within the cooler ALMA CO wind, this figure demonstrates the nested structure of disk winds.

sources ('Results'), coupled with low-velocity [O I] tracing an inner wind, strongly suggests such shielding (see Section 4.2 in ref. 16).

Among the proposed wind models, radially extended MHD winds are the only ones that are consistent with the wind morphologies and nested structures observed in our sample. Although the initial opening angles at the launch radii are ≥30°, the toroidal component of the magnetic field produces a gradual recollimation (for example, ref. 40). Field lines close to the co-rotation radius contribute to a fast axial jet, whereas those further out can explain a range of flow opening angles depending on the scale probed by the observations. With the temperature, ionization and radiation field decreasing as the launch radius increases, a nested velocity structure and morphology are expected (for example, ref. 6). H₂ and CO can survive in these winds and trace photoprocesses like those in photodissociation regions and internal shocks⁹. The one-sided winds of FS Tau B and HH 30 are aligned with

global MHD simulations that account for the non-ideal Hall effect⁴⁶, although differences in the ambient medium, more pronounced in embedded sources, might also contribute to the asymmetry (for example, ref. 34).

The rich spectral information in this NIRSpec dataset, with numerous lines of [Fe II], H₂, and CO (Fig. 1), enables the physical conditions in the wind components to be determined, including mass-loss rates (N.S.B. et al., manuscript in preparation, and T.L.B. et al., manuscript in preparation). Together, the imaging and spectroscopy will clarify whether disk winds are, indeed, sufficient to drive disk accretion. The implications of wind-driven accretion extend far beyond clarifying how disks accrete. Wind-driven accretion profoundly impacts disk dynamics and planet formation: it slows down the inward drift of solids, thus helping to overcome the radial drift barrier that hinders planet formation, and it alters the migration of planetary embryos, which
enhances the survival of close-in super-Earths⁵. Additionally, MHD winds could transport high-temperature materials from the inner Solar System to the comet-forming region⁴⁷. These effects could reshape our understanding of how planetary systems form and evolve.

## Methods

### Observations and data reduction

Our sources were observed in September 2022 with the JWST NIRSpec IFU instrument as part of our cycle 1 general observer programme (PI Pascucci, ID 1621). We adopted a four-point dither pattern to improve the sampling of the PSF, one integration with 30 groups per dither and integrated for a total on-source time of 30 min per grating. We selected all three high-resolution gratings to cover the entire wavelength range from ~0.98 to 5.2 µm.

To reduce the data, we used the JWST calibration pipeline⁴⁸ v.1.13.4.dev19+gbddb39c6, which was made available on 25 January 2024. The initial stage, Detector1Pipeline, implements detector-level corrections on a group-by-group basis. We customized the jump step within this stage to detect ‘snowballs’ in the data and flagged groups after the jump with a data number above 1,000 and any groups within the first 50 s. Subsequently, the Spec2Pipeline was executed with default parameters and NSClean on; this step includes photometric calibration, flat field correction and World Coordinate System assignment. Because of issues with the default outlier detection and rejection step within the Spec3Pipeline stage, we ran a custom script to flag very large positive and negative pixels (J. Morrison, personal communication, 2023). Following this, we ran the Spec3Pipeline with the modified cal files and created the image cubes with and without the ifalign mode. The latter avoids any further interpolation and is the preferred product for the analysis carried out in this paper. We inspected the cubes to verify that none of the scientific data were erroneously flagged.

Finally, to properly compare NIRSpec IFU data across the full wavelength range in the dataset, the measured data cubes were deconvolved at each wavelength using a corresponding model PSF. How the deconvolution model PSF is derived is described in the next paragraph. Deconvolution was carried out using the robust Bayesian-based Richardson-Lucy method⁴⁹,⁵⁰, which conserves flux. Iterations were optimized and visually inspected to ensure that resolutions were matched across the wavelength range of the datasets. The best results were obtained using 12 iterations. The deconvolution was carried out using the Python scikit-image restoration tools. Post-deconvolution, we confirmed flux conservation by comparing the flux of lines analysed in this work before and after deconvolution. We also verified that no artefacts were introduced by inspecting continuum-subtracted line maps (see ‘Continuum-subtracted line maps’ for their generation) and confirmed that the emission features sharpened to the same resolution level, with PSF broadening as a function of wavelength effectively removed.

The deconvolution model PSF was derived using the JWST WebbPSF software package⁵¹ and commissioning observations of a point source. Although WebbPSF can generate representative model PSFs for NIRSpec with time-specific optical path differential files (OPD), these models do not include the full optical path of the IFU, such as the grating distortions and IFU slicing optics. To incorporate the IFU optical path, we devised a new methodology (Beck et al. in preparation) that relies on convolving the WebbPSF models with a kernel generated from the commissioning data of a point source observed in IFU mode (Programme ID 1128). In doing this, the kernel data cube takes into account optical differences between the empirical point source data and the PSF model calculations. This kernel can, hence, be used with the appropriate WebbPSF OPD calculation at the time of an observation to create a noise-free PSF matched to any science data. The deconvolution PSF model used for this study was constructed by using the WebbPSF OPD model for the time of the observations of HH 30 (26 September 2022; with a NIRSpec wavefront error of 75 nm r.m.s.) and convolving by our kernel to match the science data presented here.

### Continuum-subtracted line maps

First, we generated total spectra summing up the flux over the entire NIRSpec IFU. These spectra are shown in Fig. 1. In addition to some of the strongest features and emission lines of interest, we also mark the NIRSpec detector gaps with semitransparent colours. Note that by plotting the minimum and maximum wavelength cutoffs of the IFU slices, we have taken the most conservative approach. The wavelength range over which flux is lost depends on the set of slices where the source flux extends. Hence, some flux is recovered in the semitransparent regions, especially for compact sources like FS Tau B.

To create line-only maps for the [Fe II] and H₂ lines, we adopted the method outlined by ref. 52. First, we used the total spectra and scipy. optimize.curve_fit to fit a Gaussian profile on top of the continuum and to determine the total flux (reported in Table 2) and the average line centroid and full-width at half-maximum (FWHM). Monte Carlo simulations showed that the uncertainty of the line flux due to the standard deviation in the nearby continuum was at most a few percent, lower than the 10% absolute flux calibration uncertainty of NIRSpec²⁰. Next, we extracted the flux at each spaxel and fitted a Gaussian plus continuum. We considered a line to be detected if the peak value of the Gaussian profile was at least three times the standard deviation of the continuum and if the standard deviation around the fitted line decreased after subtracting the best-fitting Gaussian plus continuum. When a line was detected, we calculated the area of the Gaussian for the line-only map and stored the centroid to determine which portion of the jet or wind was blueshifted. When no line was detected, we refitted only the continuum and set a $1\sigma$ upper limit for the line-only map using the standard deviation of the continuum-subtracted data and the average FWHM. The continuum-only map was derived by averaging the continuum across the line centroid ± FWHM. Although not shown here, we also generated line-only maps for the H₂ 2.12 µm and 5.05 µm transitions with integrated fluxes (Supplementary Table 1). Their morphologies were the same as that of the H₂ 0 → 0 S(9) line, which we focus on here because it suffered less than the 2.12 µm line from scattering close to the disk plane and it is brighter than the 5.05 µm line.

To construct the continuum-subtracted CO ($\nu = 1 \rightarrow 0$) map, we expanded the method above by fitting, at each spaxel, several Gaussian profiles across various wavelength segments, all sharing a common continuum. We used the ¹²CO and ¹³CO line list from the HITRAN database⁵³, supplemented by other lines within the CO ($\nu = 1 \rightarrow 0$) fundamental band (https://pdrs4all.org/seps/#highly-processed-data-products). The line-only map was generated by summing the areas of all detected ¹²CO lines. In spaxels where lines were not detected, we provided a 3$\sigma$ upper limit, calculated using the standard deviation of the data after continuum subtraction and the average ¹²CO FWHM from fitting lines in the total NIRSpec IFU spectrum.

### Jet and wind morphologies

To measure the jet PA, we used the continuum-subtracted [Fe II] 1.644 µm map generated with the default rotation in the pipeline script provided by the Space Telescope Science Institute so that north was pointing up along the y axis. For each pixel along the x axis, we extracted the corresponding y array, smoothed it and found its peak value ($\langle y \rangle$ peak). We then performed a linear fit of the x values and the identified y peaks using the sklearn RANSAC regressor. The jet PA is the angle between this best-fitting line and the direction of north. We repeated the extraction, peak identification and linear fit across different sets of $(x,y)$ points that exhibit jet emission. Next, we analysed the distribution of the jet PAs and computed the mode, the most frequently occurring PA, and the standard deviation. These are the values reported in Table 2. Note that in all cases, the jet PA is found to be perpendicular to the disk PA within the quoted uncertainties.

We determined the blueshifted side of the jet from the Gaussian line centroid map, which was constructed as discussed in ‘Continuum-subtracted line maps’. We then rotated all line-only and
continuum maps to an angle that aligned the blueshifted component of the jet with the upper part of the y axis on the panel. The jet's emission pinpoints the star's position along the x axis. However, locating the star on the y axis was more challenging due to the systems being observed close to edge-on. This orientation results in the circumstellar disk obscuring partially or completely the star's emission. For HH 30, IRAS 04302 and Tau 042021, whose disks are inclined by more than 80°, the continuum map traces the flared disk surface, with no emission near the disk plane. For these cases, we extracted a profile along the jet emission and identified the midpoint of the non-emissive, or 'dark', continuum valley. This midpoint was assigned as the star's y axis location as well as the disk plane. For FS Tau B, with the disk inclined at -70°, the continuum emission appeared point-like (Fig. 2) and probably traces scattered light in proximity to the central star. We assigned the star's y axis position to the pixel just below the peak of the continuum emission.

We used the gradual broadening of the jet emission away from the disk plane to estimate the jet semi-opening angles ($\theta_j$) reported in Table 2. First, we performed horizontal cuts across the [Fe II] rotated line-only images, fitted a Gaussian profile and measured its FWHM. Next, we assessed potential artificial broadening of the jet's FWHM due to scattering near the disk plane, along with any insufficient FWHM sampling. For FS Tau B, IRAS 04302 and Tau 042021, note that the peak of the jet emission spreads over two columns. Consequently, any FWHM measurement below 1.7 pixels (equivalent to 0.17") was considered to be undersampled. This is evidenced by the near-constant jet FWHM for FS Tau B and Tau 042021 at distances below 0.5" from the disk plane, as shown in Fig. 3. Hence, we excluded any data points with FWHM < 0.17" when determining the jets' semi-opening angles. In contrast, the peak jet emission in HH 30 was more narrowly confined along a single column, which mitigated the sampling issue. For this source, we further compared our FWHM versus distance with that obtained from higher-resolution spectral images of the [S II] 6,731 Å and [O I] 6,300 Å lines recorded by the space telescope imaging spectrograph onboard the Hubble Space Telescope³⁷ and determined that the [Fe II] jet becomes resolvable at distances greater than 1" from the disk plane. Only these resolvable points were used in our analysis. Ordinary least squares fitting was then applied to the data points unaffected by scattering or poor sampling, which are represented by filled circles in Fig. 3. The jet semi-opening angle ($\theta_j$) was calculated from the slope of the best-fitting relation. This value along with its $1\sigma$ uncertainty derived from the covariance matrix are provided in Table 2. For FS Tau B and HH 30, for which jet semi-opening angles have previously been reported in the literature³⁷,⁵⁴, our values align with the published ones within the estimated uncertainties.

The wind semi-opening angles ($\theta_w$) and geometric radii ($R_{geo}$) reported in Table 2 were measured for the rotated H$_2$ O S(9) line-only image. To trace the wind's outer contours, we developed two approaches. The first one follows ref. 55 and relies on calculating the second-order derivative of horizontal cuts across the wind emission and finding its zero values. These values indicate the inflection points that define the wind's edge. However, for complex patchy emission, like that from IRAS 04302, the method finds too many inflection points that need to be handled manually. As such, we developed a more robust approach that relies on fitting Gaussian profiles, typically two but see below, to the same horizontal cuts. We verified for HH 30 that the wind's edges from the first method are equivalent to the Gaussian centroids plus or minus half of its FWHM, depending on the wind's location with respect to the central axis. For FS Tau B and HH 30, one Gaussian ±0.5 × FWHM was used when approaching the disk plane. The Gaussian fitting method was applied to all sources and used to determine the wind's properties. Supplementary Fig. 1 demonstrates this technique for HH 30. To evaluate if the wind's shape exhibits symmetry around the central axis, we analysed the edges on either side separately. We fitted the edges versus the distance from the star using ordinary least squares. The semi-opening angles ($\theta_w$) of the wind were then calculated

as the angles between the best-fitting lines and the vertical y axis. The geometric radii ($R_{geo}$) were determined by the intersection points of these best-fitting lines with the disk's plane, marked by the star's location on the y axis. Further, $1\sigma$ uncertainties for $\theta_w$ and $R_{geo}$ were calculated and are reported in Table 2 and for the CO ($\nu = 1 \rightarrow 0$) in HH 30 in the caption of Fig. 4.

## Data availability

The JWST data used in this paper can be found at the Mikulski Archive for Space Telescope under programme IDs 1621 (ref. 56) and 1128 (ref. 57). The first programme covers the four edge-on disks, and the second has the commissioning data used to generate the NIRSpec PSF. Both raw data and fully processed pipeline data can be downloaded from the archive. The spectra integrated over the NIRSpec IFU (Fig. 1) as well as the line-only and continuum maps (Fig. 2) are available via Figshare at https://doi.org/10.6084/m9.fishshare.26387977 (ref. 58).

## Code availability

The data were reduced with the JWST calibration pipeline v.1.13.4.dev19+gbddb39c6. Upon request, the first author (I.P.) will provide the Python scripts used to analyse the data and generate the figures.

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## Acknowledgements

This work is based on observations made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with the general observer cycle 1 programme 1621 (PI I. Pascucci). I.P. and N.S.B. acknowledge partial support from NASA and the Space Telescope Science Institute (GO Grant No. JWST-GO-01621.001, PI I.P.). S.C. acknowledges funding from the funding from the Scientific Council of Observatoire de Paris and the national programme Physique et Chimie du Milieu Interstellaire of Centre National de la Recherche Scientifique, a programme operated through the Institut National des Sciences de l'Univers with Institut National de Chimie and Institut National de Physique and co-funded by the Commissariat à l'Energie Atomique et aux Energies Alternatives and Centre National d'Etudes Spatiales. K.S. and D.S. acknowledge support from the European Research Council (ERC) under the Horizon 2020 Framework Program through ERC Advanced Grant Origins 83 24 28, PI Th. Henning. G.D. acknowledges support from the ERC under the European Union's Horizon Europe research and innovation programme (Grant Agreement No. 101053020, Project Dust2Planets, PI F. Ménard). M.V. acknowledges support from the ERC under the European Union's Horizon Europe Research & Innovation Programme (Grant Agreement No. 101039651, DiscEvol, PI G. Rosotti). I.P. thanks D. Deng and F. Long for an initial exploration of the ALMA data for our sources. We acknowledge the use of the following packages: api, Astropy, NumPy, SciPy, sklearn, Matplotlib and pandas.

## Author contributions

I.P. led the proposal, carried out the analysis and wrote the paper. T.B., S.C., S.E., J.N., U.G., C.S., S.B., S.K., J.M., M.R., K.S. and D.S.

contributed to the planning and writing of the JWST proposal. N.S.B. used the JWST pipeline to perform the data reduction. T.B. assisted in planning the observations, in the data reduction and in the PSF deconvolution of the reduced data cubes. F.L. provided the ALMA CO (2→1) data for HH 30. B.S. contributed to the initial script used to generate the CO (v=1→0) map and the RGB figures. S.C., S.E., J.N. and U.G. made substantial contributions to the interpretation of the results. All authors participated in the discussion of the results or commented on the paper.

## Competing interests

The authors declare no competing interests.

## Additional information

**Supplementary information** The online version contains supplementary material available at https://doi.org/10.1038/s41550-024-02385-7.

**Correspondence and requests for materials** should be addressed to Ilaria Pascucci.

**Peer review information** Nature Astronomy thanks Manuele Gangi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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