arXiv subjects

Eduard Vorobyov

Publications and source records attributed to Eduard Vorobyov.

At least 19 recordsLinked to original sources

arXiv2026

Tracking Protostellar Variability in Massive Protoclusters with ALMA: I. Insights from QUARKS and MaMMOtH

Millimeter/submillimeter variability is often attributed to dynamical disk-mediated accretion, yet detection is limited to low-mass protostars in nearby clouds. Recent observations have also revealed significant (sub)millimeter variability in high-mass protostars, but the confirmed cases are scarce and lack systematic monitoring. In this work, we analyzed multi-epoch Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 (1.3 mm) continuum observations of 22 massive protoclusters, with epoch separations ranging from a few hours to more than two years, while achieving a consistent angular resolution of approximately 0.3 arcsec. These data allow us to track variability of protostars across a broader mass range and in an environment markedly different from nearby clouds. Using a custom processing pipeline for data reduction, image alignment, and relative flux calibration, we achieve high-precision flux measurements and, for the first time, investigate millimeter variability in massive protoclusters based on interferometric data in a statistical manner. Applying the astrodendro algorithm, we identified 383 condensations and tracked their variations in peak intensities. Standard deviation analysis and difference maps reveal five variable sources, corresponding to a lower limit of 1.3% on the variable fraction. Among these, I13111-6228 stands out as it hosts a hypercompact H II region that exhibits a 68% increase in continuum peak intensity over one year, with an uncertainty of 2%.

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arXiv2026

Modelling the Break in the Specific Angular Momentum within the Envelope-Disk Transition Zone

The observations of protostellar systems show a transition in the radial profile of specific angular momentum (and rotational velocity), evolving from $j\sim{\rm constant}$ ($v_ϕ\sim r^{-1}$) in the infalling-rotating envelope to $j\propto r^{1/2}$ ($v_ϕ\sim r^{-1/2}$) in the Keplerian disk. We employ global MHD disk simulations of gravitational collapse starting from a supercritical prestellar core, that forms a disk and envelope structure in a self-consistent manner, in order to determine the physics of the Envelope-Disk Transition Zone (ENDTRANZ). Our numerical results show the transition from the infalling-rotating envelope to Keplerian disk happens through a jump in the $j-r$ profile over a finite radial range, which is characterized by the positive local gravitational torques. The outer edge of the ENDTRANZ is identified where the radial infall speed ($v_r$) begins a sharp decline in magnitude and $j$ begins a transition from $j\sim{\rm constant}$ toward $j\sim r^{1/2}$. Moving radially inward, the centrifugal radius ($r_{\rm CR}$) is defined where $v_ϕ$ first transitions to Keplerian velocity at the disk's edge. Farther inward of $r_{\rm CR}$, model disk develops a super-Keplerian rotation due to self-gravity. The inner edge of the ENDTRANZ is defined at the centrifugal barrier ($r_{\rm CB}$) where $v_r$ drops to negligible values. Inside $r_{\rm CB}$, a net negative gravitational torque drives mass accretion onto the protostar. On observational grounds, we identify a jump in the observed $j-r$ profile in L1527 IRS for the first time using the ALMA eDisk data. Comparison with the numerical radial behavior from our MHD disk simulations suggests the observed $j-r$ jump can be used as a kinematical tracer for the existence of ENDTRANZ. Our results offer insights into the observable imprint of angular momentum redistribution mechanisms during star-disk formation.

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arXiv2026

Solar-like oscillations in accreting pre-main sequence stars: Insights and prospects

We present theoretical predictions for solar-like oscillators in the pre-main sequence phase of stellar evolution. Our pre-main sequence models start from a stellar seed of 0.01 solar masses that gains mass through accretion, offering an alternative description to the classical approach segmented into the Hayashi and Henyey tracks. Evolutionary models are calculated using the \mesa stellar evolution code with a custom accretion routine and pulsation properties are investigated using the \GYRE oscillation code. We present evolutionary tracks and internal structures for accreting pre-main sequence solar-like stars in the mass range from 0.7 to 1.6 solar masses, adopting 35 mass accretion histories previously extracted from two-dimensional magneto-hydrodynamical simulations. Atmospheric parameters of our models constrain characteristic frequencies of pre-main sequence solar-like oscillators to be generally greater than 500 $μ\text{Hz}$. We highlight the imprint of accretion on the buoyancy and Lamb profiles and illustrate the effects on the small- and large frequency separations. We additionally quantify individual frequency differences across the 35 accretion histories at the zero-age main-sequence, showcasing differences no larger than $20 \ μ\text{Hz}$ for an exemplary model. Finally, we discuss the potential of detecting solar-like oscillations in pre-main sequence stars with the upcoming ESA PLATO mission.

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arXiv2025

The Effect of Luminosity Outbursts on the Abundance of Pebbles and Their Ice Mantles in Protoplanetary Disks

Centimeter-sized dust grains-pebbles-are necessary for planetesimal formation via the streaming instability, they play an important role in forming protoplanetary cores and giant planets, as well as enriching their atmospheres with chemical elements. This work investigates the effect of luminosity outbursts on the abundance of pebbles and their ice mantles in protoplanetary disks. We perform global simulations of formation and evolution of a self-gravitating viscous protoplanetary disk using the 2D hydrodynamic thin-disk FEOSAD code, which self-consistently reproduces luminosity outbursts. The model includes thermal balance, dust evolution and its interaction with gas, development of magnetorotational instability, adsorption and desorption of four volatile compounds (H$_2$O, CO$_2$, CH$_4$ and CO), and the feedback of ice mantles on dust fragmentation properties. We show that luminosity outbursts have a stronger effect on the positions of CO$_2$, CH$_4$ and CO snowlines compared to the water snowline. This is because the H$_2$O snowline falls within the viscous heating dominated region during early disk evolution stages, while snowlines of other molecules are located in regions dominated by stellar irradiation heating and are thus more sensitive to temperature changes during outbursts. Nevertheless, luminosity outbursts reduce the total amount of pebbles in the disk by half due to destruction of dust aggregates into monomers following the loss of water ice that binds the aggregates together. Pebble recovery occurs over several thousand years after the outburst ends due to collisional coagulation, with recovery timescales significantly exceeding water freeze-out times. Ice mantle desorption occurs in a complex non-axisymmetric 2D region of the disk, associated with spiral substructure formation during early evolution of gravitationally unstable disks.

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arXiv2025

Dust in the wind of outbursting young stars

Context. Young Stellar Objects (YSOs) are observed to undergo powerful accretion events known as FU Orionis outbursts (FUors). Such events of episodic accretion are now considered to be common during low mass star formation, wherein the accretion onto the protostar occurs through a surrounding centrifugal disk. Increasing evidence suggests that the magnetic disk winds are crucial for driving disk accretion, as they carry both mass and momentum away from the disk. Aims. We aim to investigate the phenomenon of the ejection of magnetic disk winds during episodic accretion, with a focus on the dust contained within these winds. Methods. We conduct magnetohydrodynamic (MHD) simulations of formation and evolution of protoplanetary disk (PPD) in the thin-disk limit. We include evolution of dust with two populations and a realistic prescription for viscosity during outbursts, which depends on the local thermal ionization fraction. The disk evolves with the concurrent action of viscosity, self-gravity and magnetic disk winds. Results. The simulated disk displays outbursting behavior in the early stages, with the duration and frequency of the bursts, their rise times, and brightness amplitudes resembling the observations of FUors. We find that during the outbursts, the winds are over an order of magnitude more dusty, as compared to in quiescence. However, despite this increased dust content, the winds are still dust-depleted as the dust-to-gas ratio is about an order of magnitude lower than the canonical interstellar value of 0.01. The results of our numerical experiments are in general agreement with the available observational findings and they shed a light on the mechanism behind production of dusty winds during outbursting events in YSOs.

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arXiv2025

Accretion bursts in young intermediate-mass stars make planet formation challenging

We investigate the occurrence of accretion bursts, dust accumulation, and the prospects for planetesimal formation in a gravitationally unstable magnetized protoplanetary disk with globally suppressed but episodically triggered magnetorotational instability (MRI), particularly in young intermediate-mass stars (YIMSs) but with a brief comparison to low-mass counterparts. We use numerical magnetohydrodynamics simulations in the thin-disk limit (FEOSAD code) to model the formation and long-term evolution of a gravitationally unstable magnetized protoplanetary disk, including dust dynamics and growth, since the collapse of a massive slowly-rotating prestellar cloud core. Massive gas concentrations and dust rings form within the inner disk region owing to the radially varying efficiency of mass transport by gravitational instability (GI). These rings are initially susceptible to streaming instability (SI). However, gradual warming of the dust rings, thanks to high opacity and GI-induced influx of matter increases the gas temperature above a threshold for the MRI to develop via thermal ionization of alkaline metals. The ensuing MRI bursts destroy the dust rings, making planetesimal formation via SI problematic. In the later evolution phase, when the burst activity starts to diminish, SI becomes inefficient because of growing dust drift velocity and more extended inner dead zone, both acting to reduce the dust concentration below the threshold for SI to develop. Low-mass objects appear to be less affected by these adverse effects. Our results suggest that disks around young intermediate-mass stars may be challenging environments for planetesimal formation via SI. This may explain the dearth of planets around stars with $M_\ast > 3.0 \,$$M_\odot$.

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arXiv2025

Magnetic disk winds in protoplanetary disks: Description of the model and impact on global disk evolution

Canonically, a protoplanetary disk is thought to undergo (gravito-)viscous evolution, wherein the angular momentum of the accreting material is transported outwards. However, several lines of reasoning suggest that the turbulent viscosity in a typical protoplanetary disk is insufficient to drive the observed accretion rates. An emerging paradigm suggests that radially extended magnetic disk winds may play a crucial role in the disk evolution. We propose a global model of magnetic wind-driven accretion for evolution of protoplanetary disks, based on the insights gained from local shearing box simulations. Here we develop this model and constrain its parameters with the help of theoretical expectations and comparison with observations. The magnetic wind is characterized with the associated loss of angular momentum and mass, which depend on the local disk conditions and stellar properties. We incorporate the disk winds self-consistently in the code FEOSAD and study formation and long-term evolution of protoplanetary disks. We include disk self-gravity and an adaptive turbulent alpha, while the co-evolution of dust is also considered. Synthetic observations are obtained via radiation thermo-chemical code ProDiMo. The models with inclusion of disk winds satisfy general expectations from both theory and observations. The disk wind parameters can be guided by observational constraints and the synthetic observations resulting from such a model compare favorably with the selected ALMA survey data of Class II disks. The proposed magnetic disk wind model is a significant step forward in the direction of representing a more complete disk evolution, wherein the disk experiences concurrent torques from viscous, gravitational, and magnetic wind processes.

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arXiv2024

C/O ratios in self-gravitating protoplanetary discs with dust evolution

Elemental abundances, particularly the C/O ratio, are seen as a way to connect the composition of planetary atmospheres with planet formation scenario and the disc chemical environment. We model the chemical composition of gas and ices in a self-gravitating disc on timescales of 0.5\,Myr since its formation to study the evolution of C/O ratio due to dust dynamics and growth, and phase transitions of the volatile species. We use the thin-disc hydrodynamic code FEOSAD, which includes disc self-gravity, thermal balance, dust evolution and turbulent diffusion, and treats dust as a dynamically different and evolving component interacting with the gas. It also describes freeze-out, sublimation and advection of four volatile species: H$_2$O, CO$_2$, CH$_4$ and CO. We demonstrate the effect of gas and dust substructures on the distribution of volatiles and C/O ratios, including the formation of multiple snowlines of one species, and point out the anticorrelation between dust-to-gas ratio and total C/O ratio emerging due to the contribution of oxygen-rich ice mantles. We identify time and spatial locations where two distinct trigger mechanisms for planet formation are operating and differentiate them by C/O ratio range: wide range of the C/O ratios of $0-1.4$ for streaming instability, and a much narrower range $0.3-0.6$ for gravitational instability (with the initial value of 0.34). This conclusion is corroborated by observations, showing that transiting exoplanets, which possibly experienced migration through a variety of disc conditions, have significantly larger spread of C/O in comparison with directly imaged exoplanets likely formed in gravitationally unstable outer disk regions. We show that the ice-phase C/O$\approx0.2-0.3$ between the CO, CO$_2$ and CH$_4$ snowlines corresponds to the composition of the Solar system comets, that represent primordial planetesimals.

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arXiv2024

Dust growth and pebble formation in the initial stages of protoplanetary disk evolution

Aims. The initial stages of planet formation may start concurrently with the formation of a gas-dust protoplanetary disk. This makes the study of the earliest stages of protoplanetary disk formation crucially important. Here we focus on dust growth and pebble formation in a protoplanetary disk that is still accreting from a parental cloud core. Methods. We have developed an original three-dimensional numerical hydrodynamics code, which computes the collapse of rotating clouds and disk formation on nested meshes using a novel hybrid Coarray Fortran-OpenMP approach for distributed and shared memory parallelization. Dust dynamics and growth are also included in the simulations. Results. We found that the dust growth from $\sim 1~μ$m to 1-10~mm already occurs in the initial few thousand years of disk evolution but the Stokes number hardly exceeds 0.1 because of higher disk densities and temperatures compared to the minimum mass Solar nebular. The ratio of the dust-to-gas vertical scale heights remains rather modest, 0.2--0.5, which may be explained by the perturbing action of spiral arms that develop in the disk soon after its formation. The dust-to-gas mass ratio in the disk midplane is highly nonhomogeneous throughout the disk extent and is in general enhanced by a factor of several compared to the fiducial 1:100 value. Low St hinders strong dust accumulation in the spiral arms compared to the rest of the disk and the nonsteady nature of the spirals is also an obstacle. The spatial distribution of pebbles in the disk midplane exhibits a highly nonhomogeneous and patchy character. The total mass of pebbles in the disk increases with time and reaches a few tens of Earth masses after a few tens of thousand years of disk evolution. Abridged.

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arXiv2023

The influence of accretion bursts on methanol and water in massive young stellar objects

The effect of accretion bursts on massive young stellar objects (MYSOs) represents a new research field in the study of young stars and their environment. We aim to investigate the impact of an accretion burst on massive disks with different types of envelopes and to study the effects of an accretion burst on the temperature structure and the chemistry of the disk. We focus on water and methanol as chemical species for this paper. The thermochemical code of PRODIMO (PROtoplanetary DIsk MOdel) is used to perform simulation of high mass protoplanetary disk models with different types of envelopes under the presence of an accretion burst. The models in question represent different evolutionary stages of protostellar objects. We calculate and show the chemical abundances in three phases of the simulation (pre-burst, burst, and post-burst). More heavily embedded disks show higher temperatures. The impact of the accretion burst is mainly characterized by the desorption of chemical species present in the disk and envelope from the dust grains to the gas phase. When the post-burst phase starts, the sublimated species freeze out again. The degree of sublimation depends strongly on the type of envelope the disk is embedded in. An accretion burst in more massive envelopes produces stronger desorption of the chemical species. However, our models show that the timescale for the chemistry to reach the pre-burst state is independent of the type of envelope. The study shows that the disk's temperature increases with a more massive envelope enclosing it. Thus, the chemistry of MYSOs in earlier stages of their evolution reacts stronger to an accretion burst than at later stages where the envelope has lost most of its mass or has been dissipated. The study of the impact of accretion bursts could also provide helpful theoretical context to the observation of methanol masers in massive disks.

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arXiv2023

Computing the gravitational potential on nested meshes using the convolution method

Aims. Our aim is to derive a fast and accurate method for computing the gravitational potential of astrophysical objects with high contrasts in density, for which nested or adaptive meshes are required. Methods. We present an extension of the convolution method for computing the gravitational potential to the nested Cartesian grids. The method makes use of the convolution theorem to compute the gravitational potential using its integral form. Results. A comparison of our method with the iterative outside-in conjugate gradient and generalized minimal residual methods for solving the Poisson equation using nonspherically symmetric density configurations has shown a comparable performance in terms of the errors relative to the analytic solutions. However, the convolution method is characterized by several advantages and outperforms the considered iterative methods by factors 10--200 in terms of the runtime, especially when graphics processor units are utilized. The convolution method also shows an overall second-order convergence, except for the errors at the grid interfaces where the convergence is linear. Conclusions. High computational speed and ease in implementation can make the convolution method a preferred choice when using a large number of nested grids. The convolution method, however, becomes more computationally costly if the dipole moments of tightly spaced gravitating objects are to be considered at coarser grids.

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arXiv2022

The imprint of star formation on stellar pulsations

In the earliest phases of their evolution, stars gain mass through the acquisition of matter from their birth clouds. The widely accepted classical concept of early stellar evolution neglects the details of this accretion phase and assumes the formation of stars with large initial radii that contract gravitationally. In this picture, the common idea is that once the stars begin their fusion processes, they have forgotten their past. By analysing stellar oscillations in recently born stars, we show that the accretion history leaves a potentially detectable imprint on the stars' interior structures. Currently available data from space would allow discriminating between these more realistic accretion scenarios and the classical early stellar evolution models. This opens a window to investigate the interior structures of young pulsating stars that will also be of relevance for related fields, such as stellar oscillations in general and exoplanet studies.

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arXiv2022

Primordial Dusty Rings and Episodic Outbursts in Protoplanetary Discs

We investigate the formation and evolution of "primordial" dusty rings occurring in the inner regions of protoplanetary discs, with the help of long-term, coupled dust-gas, magnetohydrodynamic simulations. The simulations are global and start from the collapse phase of the parent cloud core, while the dead zone is calculated via an adaptive $α$ formulation by taking into account the local ionization balance. The evolution of the dusty component includes its growth and back reaction on to the gas. Previously, using simulations with only a gas component, we showed that dynamical rings form at the inner edge of the dead zone. We find that when dust evolution as well as magnetic field evolution in the flux-freezing limit are included, the dusty rings formed are more numerous and span a larger radial extent in the inner disc, while the dead zone is more robust and persists for a much longer time. We show that these dynamical rings concentrate enough dust mass to become streaming unstable, which should result in rapid planetesimal formation even in the embedded phases of the system. The episodic outbursts caused by the magnetorotational instability have significant impact on the evolution of the rings. The outbursts drain the inner disc of grown dust, however, the period between bursts is sufficiently long for the planetesimal growth via streaming instability.The dust mass contained within the rings is large enough to ultimately produce planetary systems with the core accretion scenario. The low mass systems rarely undergo outbursts and thus, the conditions around such stars can be especially conducive for planet formation.

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arXiv2022

Time-dependent, long-term hydrodynamic simulations of the inner protoplanetary disk II: The importance of stellar rotation

The spin evolution of young protostars, surrounded by an accretion disk, still poses problems for observations and theoretical models. In recent studies, the importance of the magnetic star-disk interaction for stellar spin evolution has been elaborated. The accretion disk in these studies, however, is only represented by a simplified model and important features are not considered. We combined the implicit hydrodynamic TAPIR disk code with a stellar spin evolution model. The influence of stellar magnetic fields on the disk dynamics, the radial position of the inner disk radius, as well as the influence of stellar rotation on the disk were calculated self-consistently. Within a defined parameter space, we can reproduce the majority of fast and slow rotating stars observed in young stellar clusters. Additionally, the back reaction of different stellar spin evolutionary tracks on the disk can be analyzed. Disks around fast rotating stars are located closer to the star. Consequently, the disk midplane temperature in the innermost disk region increases significantly compared to slow rotating stars. We can show the effects of stellar rotation on episodic accretion outbursts. The higher temperatures of disks around fast rotating stars result in more outbursts and a longer outbursting period over the disk lifetime. The combination of a long-term hydrodynamic disk and a stellar spin evolution model allows the inclusion of previously unconsidered effects such as the back-reaction of stellar rotation on the long-term disk evolution and the occurrence of accretion outbursts. However, a wider parameter range has to be studied to further investigate these effects. Additionally, a possible interaction between our model and a more realistic stellar evolution code (e.g., the MESA code) can improve our understanding of the stellar spin evolution and its effects on the pre-main sequence star.

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arXiv2022

A likely flyby of binary protostar Z CMa caught in action

Close encounters between young stellar objects in star forming clusters are expected to dramatically perturb circumstellar disks. Such events are witnessed in numerical simulations of star formation, but few direct observations of ongoing encounters have been made. Here we report sub-0".1 resolution Atacama Large Millimeter Array (ALMA) and Jansky Very Large Array (JVLA) observations towards the million year old binary protostar Z CMa in dust continuum and molecular line emission. A point source ~4700 au from the binary has been discovered at both millimeter and centimeter wavelengths. It is located along the extension of a ~2000 au streamer structure previously found in scattered light imaging, whose counterpart in dust and gas emission is also newly identified. Comparison with simulations shows signposts of a rare flyby event in action. Z CMa is a "double burster", as both binary components undergo accretion outbursts, which may be facilitated by perturbations to the host disk by flybys.

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arXiv2021

Evolution of dust in protoplanetary disks of eruptive stars

Luminosity bursts in young FU Orionis-type stars warm up the surrounding disks of gas and dust, thus inflicting changes on their morphological and chemical composition. In this work, we aim at studying the effects that such bursts may have on the spatial distribution of dust grain sizes and the corresponding spectral index in protoplanetary disks. We use the numerical hydrodynamics code FEOSAD, which simulates the co-evolution of gas, dust, and volatiles in a protoplanetary disk, taking dust growth and back reaction on gas into account. The dependence of the maximum dust size on the water ice mantles is explicitly considered. The burst is initialized by increasing the luminosity of the central star to 100-300 L_sun for a time period of 100 yr. The water snowline shifts during the burst to a larger distance, resulting in the drop of the maximum dust size interior to the snowline position because of more efficient fragmentation of bare grains. After the burst, the water snowline shifts quickly back to its preburst location followed by renewed dust growth. The timescale of dust regrowth after the burst depends on the radial distance so that the dust grains at smaller distances reach the preburst values faster than the dust grains at larger distances. As a result, a broad peak in the radial distribution of the spectral index in the millimeter dust emission develops at \approx 10 au, which shifts further out as the disk evolves and dust grains regrow to preburst values at progressively larger distances. This feature is most pronounced in evolved axisymmetric disks rather than in young gravitationally unstable counterparts, although young disks may still be good candidates if gravitational instability is suppressed. Abridged.

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arXiv2021

Eruptive Behavior of Magnetically Layered Protoplanetary Disks in Low Metallicity Environments

A protoplanetary disk typically forms a dead zone near its midplane at the distance of a few au from the central protostar. Accretion through such a magnetically layered disk can be intrinsically unstable and has been associated with episodic outbursts in young stellar objects. We present the first investigation into the effects of low metallicity environment on the structure of the dead zone as well as the resulting outbursting behavior of the protoplanetary disk. We conducted global numerical hydrodynamic simulations of protoplanetary disk formation and evolution in the thin-disk limit. The consequences of metallicity were considered via its effects on the gas and dust opacity of the disk, the thickness of the magnetically active surface layer, and the temperature of the prestellar cloud core. We show that the metal poor disks accumulate much more mass in the innermost regions, as compared to the solar metallicity counterparts. The duration of the outbursting phase also varies with metallicity - the low metallicity disks showed more powerful luminosity eruptions with a shorter burst phase, which was confined mostly to the early, embedded stages of the disk evolution. The lowest metallicity disks with the higher cloud core temperature showed the most significant differences. The occurrence of outbursts was relatively rare in the disks around low mass stars and this was especially true at lowest metallicities. We conclude that the metal content of the disk environment can have profound effects on both the disk structure and evolution in terms of episodic accretion.

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arXiv2020

Accretion bursts in magnetized gas-dust protoplanetary disks

Aims and Methods. Accretion bursts triggered by the magnetorotational instability (MRI) in the innermost disk regions were studied for protoplanetary gas-dust disks formed from prestellar cores of various mass $M_{\rm core}$ and mass-to-magnetic flux ratio $λ$. Numerical magnetohydrodynamics simulations in the thin-disk limit were employed to study the long-term ($\sim 1.0$~Myr) evolution of protoplanetary disks with an adaptive turbulent $α$-parameter, which depends explicitly on the strength of the magnetic field and ionization fraction in the disk. The numerical models also feature the co-evolution of gas and dust, including the back-reaction of dust on gas and dust growth. Results. Dead zone with a low ionization fraction $x <= 10^{-13}$ and temperature on the order of several hundred Kelvin forms in the inner disk soon after its formation, extending from several to several tens of astronomical units depending on the model. The dead zone features pronounced dust rings that are formed due to the concentration of grown dust particles in the local pressure maxima. Thermal ionization of alkaline metals in the dead zone trigger the MRI and associated accretion burst, which is characterized by a sharp rise, small-scale variability in the active phase, and fast decline once the inner MRI-active region is depleted of matter. The burst occurrence frequency is highest in the initial stages of disk formation, and is driven by gravitational instability (GI), but declines with diminishing disk mass-loading from the infalling envelope. There is a causal link between the initial burst activity and the strength of GI in the disk fueled by mass infall from the envelope. Abridged.

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