ffortissimo is a JAX-based freeform forward-modeling pipeline that fits complex dust distributions and infers scattering properties in KLIP-reduced images of circumstellar disks such as HR 4796A.
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L., P´ erez, L
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abstract
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10 AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees). We obtain a high-fidelity image of the 1.0 mm spectral index ($\alpha$), which ranges from $\alpha\sim2.0$ in the optically-thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km/s consistent with Keplerian motion around a ~1.3 solar mass star, although complicated by absorption at low blue-shifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkHa358 at 2.9 mm.
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representative citing papers
CHIBI is a new hierarchical Bayesian method for multifrequency synthesis radio imaging based on synchrotron spectral parametrization, demonstrated on VLBA MOJAVE data and simulated EHT observations of M87*.
A tree algorithm reduces multi-component coagulation complexity from O(N^{2d}) to O(d N^d log N) by grouping similar interactions and matches direct-method results in tests with analytic solutions.
JWST data on NGTS-10A b shows nightside CH4 depletion caused by day-to-night horizontal transport rather than vertical mixing or non-solar abundances.
Cavity truncation in circumbinary discs is set by binary parameters together with instantaneous cavity eccentricity and relative apsidal orientation, yielding a prescription for pericentre radius Rp and semi-major axis acav.
Presents an observability framework for solar gravitational lens astronomy and reports SSIM values of 0.993, 0.918, 0.973, and 0.923 for scalar reconstructions of four analytic scenes under stated assumptions.
Water binding energy on silicate grains is twice that on ice, enabling local retention and inheritance for terrestrial planets without outer Solar System delivery.
Irregular hexahedral dust grains yield nearly the same polarization morphology and fraction as spherical grains in self-scattering regimes but with up to 2.5 times higher scattering opacity, and are still insufficient to match observed polarization levels.
3D simulations find that initial disc tilt and binary mass ratio determine preferential accretion onto the primary or secondary star, with polar discs showing the slowest mass loss.
N-body simulations find stellar mass-loss effects dominate gravitational scattering in altering giant planet orbits around white dwarfs formed in star clusters, independent of density and initial conditions.
2D radiation-hydrodynamical simulations find accretion outbursts unstable to Rossby-wave instability, forming vortices that suppress planetesimal formation until post-burst quiescence.
Updated DALI models reproduce observed C2H2 fluxes with solar C/O and find the C2H2/H2O flux ratio sensitive to elemental abundances and small-grain abundance in planet-forming disk regions.
Simulations require 2000 Earth masses of pebbles to match observed disc gaps, but this produces mostly gas giants and few super-Earths, contradicting exoplanet data.
Nonlinear shock formation dominates angular momentum deposition from planet-induced density waves, cooling matches it for sub-thermal planets, and viscosity only matters at unrealistically high values.
Sustained mass transfer from a circumbinary disc enables giant planet formation in gamma-Cephei-like binaries by prolonging the lifetime of the circumprimary disc against truncation and photoevaporation.
Radiative-transfer simulations with common dust models generate a range of spectral indices but cannot reach the lowest observed emissivity indices in protostars without invoking unexpectedly large millimeter-sized grains.
H-type objects in IC348 show spatial distributions matching stars and brown dwarfs, unlike the more dispersed distribution of simulated ejected planets, indicating a star-like formation origin.
ALMA survey detects hot corino chemistry in 3/5 Class 0/I protostars with CH3OH column densities 10^17-10^18 cm^{-2} and rotational temperatures 200-250 K, showing two orders of magnitude variation in COM ratios.
Two migrating super-Earths in low-viscosity disks trigger narrow and broad dust substructures with high dust-to-gas ratios favorable for planetesimal formation.
The paper proposes the iSEEDs project to integrate machine learning with astrochemistry for extracting physical conditions and molecular abundances from protostellar disk datasets.
SKAO will enable the first large-scale high-resolution surveys of cm-wavelength disk emission to constrain dust growth, pebble demographics, and planet formation processes.
citing papers explorer
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ffortissimo: A Freeform Forward-Modeling Pipeline for High-Contrast Images of Circumstellar Disks Based on Automatic Differentiation
ffortissimo is a JAX-based freeform forward-modeling pipeline that fits complex dust distributions and infers scattering properties in KLIP-reduced images of circumstellar disks such as HR 4796A.
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Multifrequency Synthesis via CHIBI: Colorful Hierarchical Interferometric Bayesian Imaging
CHIBI is a new hierarchical Bayesian method for multifrequency synthesis radio imaging based on synchrotron spectral parametrization, demonstrated on VLBA MOJAVE data and simulated EHT observations of M87*.
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A fast tree algorithm for multi-component coagulation equation
A tree algorithm reduces multi-component coagulation complexity from O(N^{2d}) to O(d N^d log N) by grouping similar interactions and matches direct-method results in tests with analytic solutions.
-
Horizontal transport as a source of disequilibrium chemistry on the nightside of a hot exoplanet
JWST data on NGTS-10A b shows nightside CH4 depletion caused by day-to-night horizontal transport rather than vertical mixing or non-solar abundances.
-
Revisiting the picture of circumbinary disc truncation
Cavity truncation in circumbinary discs is set by binary parameters together with instantaneous cavity eccentricity and relative apsidal orientation, yielding a prescription for pericentre radius Rp and semi-major axis acav.
-
Ultra-High-Resolution Astronomy with the Solar Gravitational Lens
Presents an observability framework for solar gravitational lens astronomy and reports SSIM values of 0.993, 0.918, 0.973, and 0.923 for scalar reconstructions of four analytic scenes under stated assumptions.
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Astrochemical Inheritance of Terrestrial Planets Water from Local Wet Silicates
Water binding energy on silicate grains is twice that on ice, enabling local retention and inheritance for terrestrial planets without outer Solar System delivery.
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Exploring Polarized Millimeter Emission from Protoplanetary Disks with Irregular Dust Grains
Irregular hexahedral dust grains yield nearly the same polarization morphology and fraction as spherical grains in self-scattering regimes but with up to 2.5 times higher scattering opacity, and are still insufficient to match observed polarization levels.
-
Misaligned circumbinary discs around unequal-mass eccentric binaries: alignment, morphology, and binary accretion variability
3D simulations find that initial disc tilt and binary mass ratio determine preferential accretion onto the primary or secondary star, with polar discs showing the slowest mass loss.
-
White dwarf planets in star clusters: gravitational scattering versus mass-loss effects
N-body simulations find stellar mass-loss effects dominate gravitational scattering in altering giant planet orbits around white dwarfs formed in star clusters, independent of density and initial conditions.
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Planet formation at the inner edge of the dead zone II. Outbursts, rings, vortices, and suppression of planetesimal formation
2D radiation-hydrodynamical simulations find accretion outbursts unstable to Rossby-wave instability, forming vortices that suppress planetesimal formation until post-burst quiescence.
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Chemistry and IR emission of acetylene in planet-forming regions of T Tauri disks. Impact of elemental abundances and dust properties
Updated DALI models reproduce observed C2H2 fluxes with solar C/O and find the C2H2/H2O flux ratio sensitive to elemental abundances and small-grain abundance in planet-forming disk regions.
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Are the observed gaps in protoplanetary discs caused by growing planets?
Simulations require 2000 Earth masses of pebbles to match observed disc gaps, but this produces mostly gas giants and few super-Earths, contradicting exoplanet data.
-
$\alpha\beta q_\mathrm{th}$-mapping of planet-induced density wave damping in protoplanetary discs
Nonlinear shock formation dominates angular momentum deposition from planet-induced density waves, cooling matches it for sub-thermal planets, and viscosity only matters at unrealistically high values.
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A formation pathway for giant planets in S-type discs of {\gamma}-Cephei-like compact binaries
Sustained mass transfer from a circumbinary disc enables giant planet formation in gamma-Cephei-like binaries by prolonging the lifetime of the circumprimary disc against truncation and photoevaporation.
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Pristine composition or size evolution: Can current dust models reproduce emissivities observed in nearby protostars?
Radiative-transfer simulations with common dust models generate a range of spectral indices but cannot reach the lowest observed emissivity indices in protostars without invoking unexpectedly large millimeter-sized grains.
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Planet or brown dwarf? Constraints on the formation of H-type objects in IC348
H-type objects in IC348 show spatial distributions matching stars and brown dwarfs, unlike the more dispersed distribution of simulated ejected planets, indicating a star-like formation origin.
-
Organic complexity in protostellar disk candidates
ALMA survey detects hot corino chemistry in 3/5 Class 0/I protostars with CH3OH column densities 10^17-10^18 cm^{-2} and rotational temperatures 200-250 K, showing two orders of magnitude variation in COM ratios.
-
On the Dust Substructures Triggered by Two Super-Earths Migrating in Low-viscosity Disks
Two migrating super-Earths in low-viscosity disks trigger narrow and broad dust substructures with high dust-to-gas ratios favorable for planetesimal formation.
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Astrochemical Study of Early Embedded Disks
The paper proposes the iSEEDs project to integrate machine learning with astrochemistry for extracting physical conditions and molecular abundances from protostellar disk datasets.
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Demographics of planet-forming disks with the SKAO
SKAO will enable the first large-scale high-resolution surveys of cm-wavelength disk emission to constrain dust growth, pebble demographics, and planet formation processes.