arXiv subjects

Myriam Benisty

Publications and source records attributed to Myriam Benisty.

At least 19 recordsLinked to original sources

arXiv2026

Coordinated Space and Ground Monitoring of Accretion Bursts in a Protoplanetary Disk: MIRI and iSHELL observe the long-term modulation of gas within a small inner disk cavity

DQ Tau is a TTauri eccentric binary with pulsed accretion bursts regulated by its $\sim 16$-day orbital period. We have monitored this system with seven instruments from ground and space over 40 days. We present results on molecular gas variability from nine JWST-MIRI and nine IRTF-iSHELL epochs over three sequential accretion bursts with accretion luminosity pulses increasing by factors of $\sim 9$-80. A fundamental new measurement from this analysis is the line broadening of CO (from iSHELL) and H$_2$O (from MIRI) lines, which we use to estimate Keplerian radii and their variability in parallel to the line luminosity. This unprecedented dataset clearly shows that the molecular emission does not react like HI and the 5-$μ$m continuum with each accretion burst: the line luminosity and width of all hot molecular gas tracers decrease over $\sim30$-35 days, consistent with an emitting region decreasing in temperature and mass as it recedes to larger radii within the $\sim 0.2$-0.4 au inner cavity perturbed by the binary. The infrared molecular spectrum of DQ Tau is affected more by disk dynamics then by chemical changes triggered by variable accretion, supporting model expectations for chemical relaxation timescales that are much longer than the duration of these accretion bursts ($\gg 10$ days). The variability observed in all tracers in this study is consistent with a scenario where gas mass builds up near the disk edge to modulate the burst peak intensity and gas density in the inner cavity every $\sim4$-5 orbital periods. The origin of this modulation is still unclear.

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arXiv2026

exoALMA XXV: A Statistical Analysis of Gaseous Substructure in Low-Inclination Disks

Protoplanetary disks exhibit complex structure in both their gas dynamics and their temperature. Characterizing it has proven challenging, owing to the mismatch between the observed complexity and the relatively simple semi-analytical models typically used to interpret it. To augment these analyses, we apply the second-order structure function to the velocity and temperature perturbations of four low-inclination sources from the exoALMA program, each measured against a noise-only null built from the data themselves. All exhibit correlated structure. Its radial correlation length is limited by the beam in every case, which excludes non-axisymmetric structure on radial scales larger than ~1.5 pressure scale heights. In three of the four disks the structure is instead resolved and elongated in azimuth, by factors of 1.6-2.3, as expected of small-scale perturbations sheared out by Keplerian rotation. We further introduce two statistics that characterize spiral structure without tracing an arm crest: a modal power spectrum, measuring the periodicity of the azimuthal structure, and a winding contrast, measuring the radial dependence of its phase. The velocity residuals of three disks are significantly wound. MWC 758 is the only source in which the winding is coherent across the disk and shared by the temperature field. Its trailing m=1 temperature structure is consistent with the illumination of a warp, while its velocity field carries small-scale, sheared structure that could redistribute angular momentum. Because neither statistic requires a crest, both extend a quantitative description of winding to the flocculent regime, where a spiral cannot be parameterized.

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arXiv2026

Detectability of resolved hydrogen lines from the accretion shock at gas giants and their circumplanetary discs

Fewer gas giants have been caught in their accretion phase than mature ones are known. Extremely Large Telescope (ELT) instruments will have a higher sensitivity and a smaller inner working angle than tools up to now, which should increase search yields. We examine what METIS, the first-generation ELT spectrograph with R=1e5, can reveal about accreting gas giants. We focus on the accessible hydrogen recombination lines, mainly Brackett alpha and Pfund-series lines. Our approach is general but we take PDS70b as a fiducial case. It is similar to WISPIT2b. To calculate high-resolution line profiles, we combine a semianalytical multi-D description of the flow onto an accreting planet and its circumplanetary disc (CPD) with local non-LTE shock-emission models. We assume the limiting scenario of no extinction, appropriate for gas giants in gaps, and negligible contribution from magnetospheric accretion. We use simulated detector sensitivities to compute needed observing times. Both the planet- and the CPD-surface shocks contribute to the line, which has a Gaussian core but wider, asymmetrical wings. The line is much narrower than the free-fall velocity, and in fact has a nearly constant FWHM=30--40 km/s at low densities. For our fiducial accretion rate onto PDS70b, the Br-a line peak excess is as strong as the photospheric continuum, modulated mostly by H2O features. At Br-a, already the continuum of PDS 70 b yields a per-bin S/N=12 in 4h. With ProDiMo, we estimate the CPD not to hinder the detection of the line emission. The peak excess should require only 10 min to reach S/N=3. For pure shock emission, the line shape is barely sensitive to the planetary or system parameters. A complex profile would indicate that magnetospheric accretion contributes significantly. The high spectral resolution of METIS will help reveal line shapes even of faint accretors with great fidelity.

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arXiv2026

Planet formation on solar system scales

Giant planets are often regarded as primordial protoplanetary "architects". Their formation and interactions with planetesimals and other planets during and after the protoplanetary disc phase are key to setting the blueprint of the planetary systems we observe today. Catching nascent gas giants is our best opportunity to uncover these crucial steps in the planet formation process and shed light on the origins of our own solar system. Over the last decade, ALMA has revolutionised our understanding of planet formation; still, detecting signatures of Jupiter-like planets has remained out of reach. We argue that ALMA2040, a next-generation sub(mm) interferometer with improved sensitivity ($\times25$ in the continuum and $\times10$ for line emission) and a $\times3$ higher angular resolution compared to ALMA, will be sensitive to (sub)mm emission around a forming Jupiter-like planet orbiting a Sun-like star within $150\,{\rm pc}$ and allow kinematically characterising interactions of Jovian and sub-Jovian planets with their natal disc. ALMA2040 will provide unique and unprecedented insights into how gas giants carve gaps, accrete material, form satellites, and affect the architectures of their co-evolving planetary systems.

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arXiv2026

Chemistry on solar system scales

The initial chemical composition of planets, primitive bodies in our solar system, and exoplanets is ultimately set by their nascent protoplanetary disks. Yet observing key carbon-, oxygen-, and nitrogen-bearing molecules (as well as rarer but important sulphur- and phosphorus-bearing species) in the inner (exo)planet-forming zone ($\lesssim 10$~au) remains extremely challenging with current facilities. Therefore, to construct a complete picture of the chemistry of planet formation and understand how (exo)planetary composition is set by physical and chemical processes within the protoplanetary disk, a more powerful observing facility, i.e., ALMA2040, is needed. Compared to current ALMA (the Atacama Large Millimeter/submillimeter Array) this new facility must provide >~ a factor of 10 in line sensitivity at a spatial resolution of <~ 5 au at 140 pc, i.e., a factor of 3 - 4 better resolution to low surface brightness emission than currently possible. This distance includes many star-forming regions such as Taurus and Lupus that are host to populations of Sun-like stars. ALMA2040 will enable mapping of disk chemical composition on terrestrial planet-forming scales (within the water snowline) and detect molecules that are the feedstock for potentially habitable worlds.

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arXiv2026

Bridging the gap between stars and planets

The formation mechanisms of brown dwarfs (BDs) and free-floating planets (FFPs) are poorly constrained. The two main competing scenarios include the star-like scenario, where these objects correspond to the least massive gravitationally unstable fragments of molecular clouds, and the planet-like scenario, where these objects form in a circumstellar disk and are subsequently ejected after a dynamical interaction. A new generation millimeter interferometer, such as ALMA2040, is required to disentangle the relevance of these scenarios. For this, ALMA2040 must provide the appropriate performance to explore BD/FFP formation from the cloud scale (~10 pc) down to the disk scale (~10 au). At cloud scales, ALMA2040 must detect a ~1 Mjup embedded FFP in the outer Galaxy (~10 kpc) in 1 h, or the same object in nearby clouds (<~ 400 pc) in about tens of seconds so that large-scale surveys of entire clouds can be performed. This would provide key censuses to compare the results with the predictions from each scenario. At disk scales, ALMA2040 must detect CO outflows from first hydrostatic cores in the substellar regime and potential molecular outflows from ~1 Mjup FFPs in nearby clouds, both with specific predictions in the star-like scenario. In addition, the planet-like scenario predicts a disk mass-to-star mass ratio for BDs larger than the star-like case, and testing this requires detecting disks of ~2 Earth masses around young BDs. Furthermore, the predicted emission for the star-like case of complex organic molecules in proto-BDs at 400 pc must be detected with ALMA2040, requiring a factor of 10 increase in line sensitivity at a spatial resolution of 5-10 au. Finally, ALMA2040 must detect Earth-like protoplanets around young BDs at 400 pc, in order to provide key observational constraints on the radial drift behaviour and planet formation mechanisms in the substellar regime.

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arXiv2026

An ALMA view on molecular complexity: water, methanol, and methyl formate in the HD 100546 and IRS 48 disks

Water and methanol are the fundamental constituents of interstellar and cometary ices: understanding their abundances in disks is therefore of high importance to reveal how this ice reservoir evolves across the timeline of star and planet formation. We present ALMA band 5 line emission observations of water and methanol in the warm Herbig disks of HD 100546 and IRS 48. While the IRS 48 disk is methanol-rich, water vapor is not detected, implying a high methanol-to-water column density ratio >0.2, possibly reflecting a distinct ice composition. Methanol and water are both detected in the HD 100546 disk, leading to a CH3OH/H2O ratio of ~0.02, consistent with the median of the cometary distribution and with the lower edge of the distribution of Young Stellar Objects. We suggest that the gas-phase methanol-to-water ratio in the HD 100546 disk directly reveals the ice reservoir subsequently sublimated in the warm disk stage. Moreover, we report a methyl formate-to-methanol ratio in the IRS 48 disk of ~0.2, consistent with the upper edge of the distribution of Young Stellar Objects. The methyl formate-to-methanol ratio in the HD 100546 disk is ~2, much higher than in younger and older sources, possibly reflecting a chemical enhancement of gas-phase methyl formate. We additionally constrain non-LTE conditions, optical depths, and emitting regions of the methanol lines in both disks. These results offer a new opportunity to probe the chemical trail of molecular complexity in the intermediate disk stage, bridging early and late phases of the star and planet formation history.

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arXiv2026

Mapping the WISPIT2 Planet-Hosting Cavity at Sub-Hill-Radius scales

We present new deep, very high angular resolution observations of the sub-mm continuum (19x13 mas) and 12CO (67x52 mas) emission from the disk surrounding the planet host WISPIT2. Our analysis reveals a clear gas gap carved by WISPIT 2b and an empty cavity within the orbit of WISPIT 2c. We also find a gaseous and optically thin dusty ring located between the orbits of the two planets. Channel maps show a pronounced change in the emission surface height of the disk, which transitions from flat within the cavity to strongly flared beyond the orbit of planet b, producing clear breaks in the velocity channels. A pronounced thunderbolt-shaped feature, identified as a kinematic planetary signature (KPS), is detected at the location of WISPIT 2b, in agreement with predictions from planet-disk interaction simulations. This constitutes the first system with a confirmed kinematic signature associated with a directly imaged planet. By mirroring opposite velocity-channel maps about the systemic velocity, we further investigate the KPS and identify spatially resolved excess emission in the vicinity of WISPIT 2b. We find that this emission is resolved across the full Hill sphere of the planet, significantly exceeding the expected extent of a circumplanetary disk. We therefore suggest that the observed emission arises from a combination of processes, including prominent planet-driven spiral wakes, localized heating induced by the planet and a circumplanetary disk. Although higher spectral resolution is required to disentangle these contributions, our observations demonstrate the potential to directly characterize the birth environment of forming massive planets at scales down to sub-Hill radius.

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arXiv2026

Dust Substructures and Line Perturbations driven by a Forming Planet in J16120

Hints of planet formation have been independently reported within the gap of the disc around 2MASS J16120668-301027 from millimetre continuum, infrared, and H-alpha observations. In this work, we present new evidence for ongoing planet formation based on Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations, detecting 0.87 mm dust continuum emission together with 12CO (J=3-2) and 13CO (J=3-2) line emission. Visibility modelling of the continuum data reveals an inner disc and two dust rings peaking at 23 and 75 au. The continuum morphology is better reproduced by an eccentric disc model (e approximately 0.1) than by an axisymmetric disc. We further investigate the gas kinematics through modelling of the 12CO channel maps. The residual line-width map shows a localised increase in velocity dispersion at the position of a previously reported circumplanetary disc candidate (deprojected radius approximately 32 au, position angle approximately 170 degrees) and along its orbit. This signal is spatially coincident with kink-like features and a transition from sub-Keplerian to super-Keplerian velocities. In addition, the velocity residual map exhibits an arc-like structure extending outward from the planet candidate, while the gas kinematics, despite substantial uncertainties, is consistent with inflow towards the candidate's orbital radius. The observed increase in velocity dispersion agrees with predictions from planet-disc interaction simulations, which produce enhanced turbulence both at the planet location and along its orbital path. Taken together, the continuum morphology and gas kinematic signatures provide compelling new evidence for ongoing planet formation within the disc gap.

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arXiv2026

Dust characterization of the HD 163296 disk with high-resolution multi-wavelength ALMA observations

Context. Planets form through the growth and accumulation of dust grains in protoplanetary disks. Characterizing dust properties such as size, surface density, and temperature is key to understanding planet formation. Aims. We characterize the dust properties of the protoplanetary disk around HD 163296 by performing spectral energy distribution (SED) fitting of multi-wavelength high-resolution observations. Methods. We present new high-resolution ALMA Band 9 (0.45 mm) observations, which are sensitive to the temperature. We performed SED fitting at a common resolution of 0.066 arcsec using these new Band 9 observations along with archival ALMA Band 3, 4, 6, and 7 observations. We compared the fitted results with VLA observations and explored multiple dust models with different optical constants and porosities. Results. The Band 9 image shows the central disk, two rings at 0.67 and 1.00 arcsec, and outer extended emission previously seen at other wavelengths. At higher frequencies, the rings appear wider, the gaps appear shallower, and the extended emission appears brighter, which can be explained by optical-depth effects and/or size segregation. We characterized the dust properties, including temperature, surface density, and dust size, for each dust model. However, the inferred dust properties are dependent on the dust model, and the ALMA data alone do not allow us to determine which dust model is preferred. We identified the DSHARP Zubko (porous) model as the preferred model based on VLA profiles and physical and observational constraints. The outer ring temperature is lower than predicted by a passively irradiated disk model, suggesting shadowing by the inner ring. Although the surface density and dust size depend on the dust model, the preferred model indicates that the central disk, both rings, and the extended disk each contain more than a few Earth masses of dust.

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arXiv2026

A closer look at the WISPIT 2 host star. Evidence for a spectroscopic binary

While hundreds of protoplanetary discs have been studied in great detail, the detection of protoplanets still embedded in their native discs remains rare. WISPIT 2 is only the second laboratory allowing for direct study of planet formation while in progress. The recently discovered system hosts two giant protoplanets in a multi-ringed disc. Here, we aim at characterising the WISPIT 2 host star spectroscopically to determine its stellar properties, accretion rate, and inner disc diagnostics, providing a more complete picture of the system. We present optical and near-infrared spectroscopic observations obtained with the ESO VLT/X-Shooter and 2.2 m/FEROS instruments. We model the stellar spectrum to determine the spectral type and effective temperature, analyse the emission lines to estimate the accretion rate, and search for evidence of a close stellar companion using radial velocity measurements. Our observations reveal that WISPIT 2 is a spectroscopic binary. The binary has a period of $4.8\pm 0.1$ days, which corresponds to a semi-major axis of $0.072$ au or $15.54 R_\odot$, assuming co-planarity with the disc and a circular orbit. The binary system consists of a $\sim 0.97 M_{\odot}$ primary of spectral type K3 ($T_{\rm eff} \sim 4700K$), and a $\sim 0.33M_\odot$ secondary (mass ratio $\sim$0.34). We detect weak H$α$ emission, implying an accretion rate of $\sim 2 \times 10^{-11}\,M_{\odot}\,\mathrm{yr}^{-1}$. However, this value is below the chromospheric level, suggesting little to no ongoing accretion onto the young stars. This discovery makes the WISPIT 2 disc the first circumbinary system with directly imaged protoplanets, establishing this system as a unique benchmark for studying planet formation and disc evolution around binary stars.

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arXiv2026

A Streamer Driving Misalignment in the Circumtriple Disk of GW Ori

GW Orionis is a triple stellar system with a disk featuring three misaligned dust rings. We present ALMA molecular line data of CO isotopologues, revealing a streamer feeding the disk in $^{12}$CO and $^{13}$CO. Through multi-pointing observations, we find the streamer extends to $\sim30''$ on-sky ($\sim12,000$~AU) and estimate a mass of 1.6 M$_{\rm Jup}$ using $^{13}$CO. Fitting the morphology and kinematics of the streamer, we estimate the mass infall timescale of 0.04 Myrs and a mass infall rate of $3.6\times10^{-8}$~M$_{\odot}$~yr$^{-1}$, approximately an order of magnitude lower than the stellar accretion rate. Our best-fit trajectory shows that the streamer meets the disk at the outermost dust ring and that the streamer's angular momentum vector is closely aligned with this outermost ring within $\approx3^\circ$, in contrast to the $\approx32^\circ$ misalignment with the innermost ring, suggesting the streamer is the likely cause of the misalignment. However, the total angular momentum of the streamer is smaller than that of GW Ori's disk; this, together with the low accretion rate, indicates that we are probably witnessing the end stages of infall. Total Power observations reveal bright emission connecting the streamer to the surrounding star-forming region, with a projected distance falling well within the Bondi-Hoyle radius, implying the streamer could have originated through Bondi-Hoyle accretion as GW Ori moves through its natal cloud. Together, these results suggest that GW Ori remains dynamically linked to its parental cloud through ongoing accretion, with the streamer serving as the likely driver of its misaligned disk structure.

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arXiv2026

Interpreting the scattering surface in protoplanetary disks

In recent years, extreme adaptive optics have enabled high-resolution, high-contrast scattered-light observations of protoplanetary disks. Interpreting these observations requires an understanding of the scattering surface, which is shaped by the distribution of small dust grains and determines how disks appear in scattered light. We aim to exploit measurements of the scattering surface height to directly constrain the masses of small dust grains in disks. Starting from radiative transfer principles, we developed a semi-analytical model of the stellar radiation path and its interaction with the disk, deriving the height of the scattering surface as a function of disk parameters such as mass, temperature, and opacity. We validated our predictions against the radiative transfer code MCFOST. Using measured scattering heights, we inferred the mass of dust in small grains and the particle size distribution for a sample of ten disks. We confirm previous results indicating that the scattering surface coincides with the region where the integrated optical depth along the stellar path is of order unity. The thermal structure of the disk significantly affects the surface height, while dust settling and anisotropic scattering have comparatively minor effects. Applying our model to observations, we measure global small-dust mass fractions of order (10^{-3}). Using dust-opacity models, we show that these values are consistent with modest grain growth ((a_{\rm max} \gtrsim 0.1,{\rm mm})) and grain-size distribution power-law indices of approximately 3--3.5, as commonly predicted by grain-growth models. Scattering-surface measurements, together with constraints on the disk thermal structure, provide a powerful method for determining the small-dust content of protoplanetary disks.

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arXiv2026

Azimuthal molecular variations in the AB Aur planet-forming disk

Late infall episodes are emerging as an important driver of disk evolution. Observed as filamentary streamers in molecular lines and scattered light, such accretion perturbs disk structures, yet its chemical consequences remain unconstrained. We present NOEMA 1.2 mm observations of AB Aur, a structured young Herbig disk showing evidence for ongoing infall and planet formation. We detect azimuthal chemical diversity: SO emission is enhanced in the northern disk near the inferred streamer-disk interaction region, while C$_2$H peaks on the opposite southern side; CS forms a nearly axisymmetric ring. HCN and HCO$^+$ peak near the dust continuum overdensity in the dust ring. Rotational diagram analyses show higher SO rotational temperatures and column densities in the north, whereas CS remains axisymmetric with lower rotational temperatures, suggesting that the species probe different disk layers. For C$_2$H, temperature variations may contribute to but cannot fully explain the asymmetries. The HCO$^+$/H$^{13}$CO$^+$ line ratio indicates that HCO$^+$ is optically thick across the molecular ring, while the elevated ratio inside the cavity suggests enhanced gas-phase $^{12}$C/$^{13}$C, consistent with isotope-selective photodissociation. Comparison with chemical models favors gas-phase C/O ratios near or above unity, with higher effective C/O in the C$_2$H-bright sector. We discuss two origins for the chemical asymmetries: (i) infall-induced heating and desorption of O-bearing ices enhance SO and lower gas-phase C/O near the streamer's impact site, and (ii) planet-driven substructures and localized heating or enhanced UV irradiation promote hydrocarbon-rich chemistry in the southern disk. These results highlight that environmental accretion and planet formation can jointly imprint azimuthal variations in disk chemistry, with potential impacts on forming planets' compositions.

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arXiv2026

MINDS: Complementary inclinations in the binary system HK Tau reveal gas- and ice-phase chemistry

[Abridged] HK Tau is a roughly equal mass pre-main sequence binary system consisting of a low-inclination primary (57 deg) and an edge-on (83 deg) secondary. We present JWST/MIRI observations targeting both sources, taken as part of the JWST GTO program MINDS. The spectra reveal a line-rich, CO2-dominated primary and a line-poor secondary; this evidence, albeit in line with the evolutionary-motivated trend uncovered by recent observations of binaries at MIRI wavelengths, is likely due to the different configuration of the two sources. Indeed, thermochemical disc models coupled with radiative transfer show that, at inclinations comparable to that of HK Tau B, only ionised atomic lines are expected to remain visible in the spectra. While blocking molecular emission lines, however, the edge-on configuration allows ice absorption bands to be visible against the continuum; in this framework, the HK Tau system provides an unprecedented opportunity to have a simultaneous view of the solid and gaseous component of a pair of coeval protoplanetary discs, thanks to the complementary inclination of the two sources. We detect water ice at 6.2 and 13.6um, CO2 ice at 15.2um, and NH4+ ice at 6.85um in the spectrum of HK Tau B; an additional absorption band between 8.3 and 9um is compatible with both silicate stretching and C-H bending. Neither of the two sources show signs of PAHs. Extended H2 emission is present around both discs, although much more elongated in HK Tau B. The distinctive 'X' shape centred in B, combined with the intensity, morphology, and spectral characteristics of the ionised atomic lines [Ar II], [Ne II], and [Ne III] suggests a low-velocity wind origin with a wide (~ 70 deg) semi-opening angle. The lower forbidden line fluxes and smaller extent of the H2 emission around A imply that, if a wind is launched from the primary as well, it is too cold or dense to be ionised.

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arXiv2026

The asymmetric carbon-rich chemistry of the planet-forming disk of HD 142527 triggered by late infall

The planet-forming disk of HD 142527 is known for its azimuthally asymmetric dust trap, shadows, and spiral arms. We use new ALMA observations to investigate the molecular composition and to determine the ongoing chemical processes and the origin of its asymmetric molecular emission. The observations cover a wide variety of molecular species, enlarging the known molecular inventory of this system. Strikingly, the emission of H$_2$CO, CN, and C$_2$H is dominated by spiral-like features peaking in the southern region of the disk, opposite to the large dust trap, while no relation is found between the observed asymmetries and the shadows seen in the scattered light. We attribute these features to low-density, late infalling, atomic carbon-rich material that locally enhances the C/O-ratio and, subsequently, facilitates the gas-phase formation of these species. The emission of C$^{17}$O and the HCO$^+$ $J$=1-0 transition is aligned with the large dust trap, likely due to an azimuthal enhancement in the surface density. Differences between the two observed C$^{17}$O transitions may be due to dust obscuration effects. This is not expected to affect molecular emission at 3 millimetres, given the lower optical depth of the dust trap. The four observed transitions of CS display different azimuthal extents and strengths, with the lines with lower upper level energies appearing more ring-like. An analysis of the $^{13}$CO brightness temperature yields no significant azimuthal temperature variations. Therefore, we propose that the observed CS transitions trace two different reservoirs: a cold reservoir that resides on a Keplerian orbit and a second, hotter reservoir of CS that is facilitated by the infalling material. A single weak transition of SO is observed, which may be explained by weak shocks induced by the spirals observed in the scattered light that liberate sulphur.

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arXiv2026

An archival summary: 15 years of ALMA observations on disks and planet formation

The Atacama Large (sub-)millimeter Array (ALMA) has been in scientific operations for almost 15 years. We celebrate this achievement by providing a summary of the ``Disks and planet formation'' scientific category, with an emphasis on the disks located in the nearby star-forming regions. As of the beginning of February 2026, ALMA had observed 3933 independent coordinates, which we analyzed by their location in the sky, frequency coverage, exposure time, spectral line coverage, and angular resolution. We encourage the community to explore new scientific questions that are made possible through the archival datasets.

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arXiv2026

Diverse dust vertical height and settling strength conditions in protoplanetary discs

The settling of dust particles plays a critical role in the growth and dynamics of dust grains. We performed a detailed modeling of the ALMA continuum substructures for six highly inclined protoplanetary discs using radiative transfer simulations, to constrain the vertical height of millimetre dust grains and the settling strength. Our modeling results are a very thin millimetre dust disc in T Cha ($\text{h}_{\text{dust}}<$ 0.1 au throughout the disc), a vertically extended dust disc in DoAr 25 ($\text{h}_{\text{dust}}$ of $\sim$ 4.7 au at 140 au) and tentatively a thin disc in MY Lup ($\text{h}_{\text{dust}}<$ 0.5 au at 70 au). From lower resolution observations we found a very thin disc for PDS 111 ($\text{h}_{\text{dust}}<$ 0.1 au throughout the disc) and a more vertically extended millimetre dust disc in V409 Tau ($\text{h}_{\text{dust}}$ of $\sim$ 1.3 au at 35 au). We could not measure the vertical height in the asymmetric disc of RY Lup. We also found that the input dust opacities are a source of degeneracy in our models. Our tentative results, assuming the Ricci dust opacities, point to a diverse settling strength in our sample and possible radial variations. We also compared the models that best fit the ALMA data with the SPHERE data to test if they can reproduce the vertical distribution of small dust grains. This comparison suggests that models that reproduce the dust density distribution in the midplane cannot reproduce the distribution of small dust grains in the upper layers, reinforcing the need for more complex models.

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