arXiv subjects

L. -A. Hühn

Publications and source records attributed to L. -A. Hühn.

5 recordsLinked to original sources

arXiv2026

Spiral formation caused by late infall onto protoplanetary disks

The classical picture that planet formation occurs in protoplanetary disks that are isolated from their environment is undergoing a major shift toward a more connected picture. An increasing amount of evolved disks are found to be actively interacting with their environment, often showing various types of spiral structures. In this work, we aim to investigate if these spirals can be a direct result of ongoing late infall using the grid-based 3D hydrodynamics code FARGO3D. We perform a detailed analysis of the spiral properties and appearance in scattered light and CO line emission using the radiative transfer code RADMC3D. In scattered light, we find both well-defined spirals with few arms (m=2) and more flocculent structures: The gradual accretion of gas remnants after a major accretion event has the most success in the former, whereas active accretion via streamers favors the latter. The m=2 spirals we find have a very low pattern speed, making them easily discernible from spirals caused by a perturber. We also find spiral patterns in the $^{12}$CO residual motions, but their morphology does not match the one found in scattered light. The disk perturbations are strongest in the upper layers (z>4H), which is reflected by the reduced amplitude of the residual motions in the more optically thin $^{13}$CO emission. Moreover, we find that the formation of m=2 spirals is not promoted in disks with lower mass, despite being more susceptible to deeper kinematic perturbations. While the late-infall streamers impact planet formation directly through the delivery of fresh material, we show that the midplane remains unperturbed unless the infalling mass is of the same order of magnitude as the disk mass. Planet formation can therefore only be impacted by late infall through secondary mechanisms that lead to dust trapping or the generation of turbulence starting from surface-level perturbations.

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arXiv2025

Emergence of streamers in simulations of late infall

Growing observational evidence suggests that Class II protoplanetary disks may undergo substantial interactions with their environment in the form of late infall. This mass inflow predominantly manifests itself in the form of so-called streamers: filaments and arcs of gas connecting large-scale, extended gas structures to disk scales. Prevalent late infall has far-reaching consequences for planet formation theory, challenging the long-standing treatment of evolved disks in isolation. In this work, we investigate the emergence of late-infall streamers in different formation scenarios, their morphology and multiplicity, as well as their dependence on environmental conditions. We conduct this investigation by performing 3D hydrodynamical simulation using the grid-based code FARGO3D, which we post-process to obtain synthetic observations using the Monte Carlo radiative transfer code RADMC3D. We find that, while a late infall event in the form of a single encounter with a "cloudlet" of gas can produce a streamer via an interplay between the fallback of bound material and shocks, such features dissipate quickly, on a timescale of ~10 kyr. Furthermore, we find that streamers can also form naturally in a turbulent, dense environment without the need for such encounters, which could act to reconcile short-lived streamers with ubiquitous detection of these structures. Here, we find multiple co-existing streamers for a disk velocity relative to the interstellar medium of $v_\mathrm{sys}=0.5~\mathrm{km}~\mathrm{s}^{-1}$ and a turbulent velocity dispersion of $σ_\mathrm{turb}=0.5~\mathrm{km}~\mathrm{s}^{-1}$. We find considerable dependence of the streamer morphology on the environment, which may act as a utility to constrain the physical conditions of the gas surrounding planet-forming disk, and therefore the conditions under which planets form.

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arXiv2025

Late accretion offers pathway to misaligned disk around the planet-hosting IRAS 04125+2902

We present a 3D hydrodynamical simulation of the accretion of a gas cloudlet onto the IRAS 04125+2902 binary system, where the 3-Myr primary hosts a transiting planet. We demonstrate that such an accretion event can naturally produce a circumstellar disk that is misaligned with respect to the rest of the system, consistent with the observed misaligned transition disk. In the model, the prescribed orbital plane of the cloudlet is largely retained by the resulting circumstellar disk after undergoing gravitational interactions with the secondary during the initial accretion. After ~4.4 binary orbits, a disk with $R_d=300~\mathrm{AU}$ has formed around the stellar primary made of ~13% of the cloudlet mass, $M_\mathrm{d,p}=2.1\times 10^{-3}~\mathrm{M}_\odot$. The companion also retains some of the cloudlet's mass and forms a disk with $M_\mathrm{d,c}=9.3\times 10^{-5}~\mathrm{M}_\odot$, though only the transition disk around the primary has been observed. Our findings highlight the importance of considering mass inflow onto protoplanetary disk for their evolution.

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arXiv2025

Planetesimal formation via the streaming instability in simulations of infall dominated young disks

Protoplanetary disks naturally emerge during protostellar core-collapse. In their early evolutionary stages, infalling material dominates their dynamical evolution. In the context of planet formation, this means that the conditions in young disks are different from the typically considered disks where infall has subsided. High inward velocities are caused by the advection of accreted material which is deficient in angular momentum, rather than being set by viscous spreading, and accretion gives rise to strong velocity fluctuations. Therefore, we aim to investigate when it is possible for the first planetesimals to form and subsequent planet formation to commence. We analyze the disks obtained in numerical 3D nonideal magnetohydrodynamical simulations, which serve as a basis for 1D models representing the conditions during the Class 0/I evolutionary stages. We integrate the 1D models with an adapted version of the TwoPopPy code to investigate the formation of the first planetesimals via the streaming instability. In disks with temperatures such that the snow line is located at ~10 AU and where it is assumed that velocity fluctuations felt by the dust are reduced by a factor of 10 compared to the gas, ${\sim}10^{-3}M_\odot$ of planetesimals may be formed already during the first 100 kyr after disk formation, implying the possible early formation of giant planet cores. The cold-finger effect at the snow line is the dominant driver of planetesimal formation, which occurs in episodes and utilizes solids supplied directly from the envelope, leaving the disk solid reservoir intact. However, if the cold-finger effect is suppressed, early planetesimal formation is limited to cold disks with efficient dust settling whose dust-to-gas ratio is initially enriched to $ε_0\geq 0.03$.

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arXiv2021

The Kepler-223 resonance holds information on turbulence during the gas disk phase

Many fundamental physical processes regarding planetary formation in protoplanetary disks are still imperfectly understood, with an elusive phenomenon being turbulence in such disks. Observations are available of planetary systems and of some protoplanetary disks, which can serve as a starting point for these investigations. Detected systems reveal different architectures of planets. One particularly interesting case to consider is the Kepler-223 system, which contains a rare configuration of four planets in a resonance chain, implying a certain migration history. We aim to use the orbital configuration of Kepler-223's planets to constrain the parameters of the protoplanetary disk that allow for the formation of a chain of mean-motion resonances that resembles the one of Kepler-223. The parameters we aim to investigate are primarily the disk viscosity and surface density. We use the swift_symba N-body integrator with additional dissipative forces to mimic planet-disk interactions. We constrain the surface densities and viscosities that allow the formation of a resonant chain like that of Kepler-223. We find that surface densities of up to a few minimum mass solar nebula (MMSN) surface densities and disk viscosity parameters $α$ of a few $10^{-3}$ up to $10^{-2}$ are most successful at reproducing the architecture of this particular planetary system. We describe how these two quantities are linked to each other considering the success of reproducing the chain and find that higher disk surface densities in turn require lower viscosities to build the chain. Our results show that well characterized observed planetary systems hold information about their formation conditions in the protoplanetary disks and that it is possible to extract this information, namely the initial disk surface density and viscosity, helping to constrain planet formation.

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