skyscapes.disk.grater

skyscapes.disk.grater#

GraterDisk: Augereau 1999 scattered-light disk as an eqx.Module.

The Augereau et al. 1999 model is a two-power-law dust density distribution with a flared vertical profile, scattering with a single Henyey-Greenstein phase function. This module exposes the model in skyscapes’ eqx.Module idiom so its parameters are PyTree leaves (fittable through the standard scene-as-PyTree pattern).

References:

Augereau, J.-C., Lagrange, A.-M., Mouillet, D., Papaloizou, J. C. B., & Grorod, P. A. 1999, A&A, 348, 557 grater-jax (Kondapalli, Lewis, Ashcraft, Millar-Blanchaer):

Notes on convention:

Disk orientation (incl_deg / pa_deg) is passed in at surface_brightness time rather than stored on the disk – the System’s midplane_inc_deg / midplane_pa_deg drives every component consistently and there is one source of truth.

Wavelength dependence enters via the HG asymmetry parameter g_HG and the albedo-like scaling Ag, both stored as 1-D grids over wavelengths_nm and interpolated at call time with a cubic spline. The geometric kernel itself is wavelength-independent, so surface_brightness keeps its scalar-in / (ny, nx)-out shape contract; vmap over wavelength gives a cube without changing the interface.

The LOS-around-midplane sampling diverges at edge-on geometry (cos(incl) -> 0); surface_brightness raises via eqx.error_if if the requested inclination is closer to edge-on than the disk’s geometric capacity allows. The threshold is arctan(rmax_AU / zmax_AU) where zmax_AU is evaluated at the outer disk radius after flaring.

Classes#

GraterDisk

Augereau 1999 scattered-light disk.

Functions#

henyey_greenstein(cos_phi, g)

Henyey-Greenstein single-scattering phase function.

two_power_law_density(r, z, sma_AU, alpha_in, ...)

Augereau 1999 two-power-law radial density with flared vertical profile.

Module Contents#

skyscapes.disk.grater.henyey_greenstein(cos_phi, g)[source]#

Henyey-Greenstein single-scattering phase function.

Args:

cos_phi: Cosine of scattering angle, any broadcastable shape. g: Asymmetry parameter in (-1, 1). g > 0 is forward-peaked,

g < 0 is backward-peaked, g = 0 is isotropic.

Returns:

Phase function value, same shape as cos_phi.

Parameters:

  • cos_phi (jaxtyping.Array)

  • g (jaxtyping.Array)

Return type:

jaxtyping.Array

skyscapes.disk.grater.two_power_law_density(r, z, sma_AU, alpha_in, alpha_out, ksi0_AU, gamma, beta)[source]#

Augereau 1999 two-power-law radial density with flared vertical profile.

Args:
r: Cylindrical radius in disk frame [AU]. Must be strictly positive;

callers are responsible for masking r values that are too small for the radial power law to evaluate cleanly in the chosen dtype (e.g. r_ratio^(-2 alpha_in) overflows float32 below r/sma ~ 1e-3 at alpha_in = 5).

z: Height above disk midplane [AU]. sma_AU: Reference radius (radial profile peak) [AU]. alpha_in: Inner power-law slope (positive convention). alpha_out: Outer power-law slope (negative convention). ksi0_AU: Vertical scale height at r = sma_AU [AU]. gamma: Vertical profile exponent (2 = Gaussian, 1 = exponential). beta: Flaring index (0 = none, 1 = linear).

Returns:

Density in arbitrary units (relative), same shape as r and z.

Parameters:

  • r (jaxtyping.Array)

  • z (jaxtyping.Array)

  • sma_AU (jaxtyping.Array)

  • alpha_in (jaxtyping.Array)

  • alpha_out (jaxtyping.Array)

  • ksi0_AU (jaxtyping.Array)

  • gamma (jaxtyping.Array)

  • beta (jaxtyping.Array)

Return type:

jaxtyping.Array

class skyscapes.disk.grater.GraterDisk[source]#

Bases: skyscapes.disk.base.AbstractDisk

Augereau 1999 scattered-light disk.

Attributes (PyTree leaves, fittable):

sma_AU: Reference radius [AU] (radial profile peak). alpha_in: Inner power-law slope (positive). alpha_out: Outer power-law slope (negative). ksi0_AU: Vertical scale height at sma_AU [AU]. gamma: Vertical profile exponent (2 = Gaussian). beta: Flaring index (0 = none, 1 = linear). rmin_AU: Inner truncation radius [AU]. rmax_AU: Outer truncation radius [AU]. wavelengths_nm: 1-D wavelength grid for g_HG_grid /

Ag_grid, shape (n_wave,) [nm]. Must be sorted. surface_brightness calls outside this range return NaN.

g_HG_grid: Henyey-Greenstein asymmetry at each grid wavelength. Ag_grid: Albedo-like scaling at each grid wavelength.

Static attributes (compilation-time constants):

nx, ny: Output image shape. pixel_scale_arcsec: Pixel scale [arcsec/pixel]. dist_pc: System distance [pc]. n_slices_los: Number of LOS integration slices. n_scale_heights: LOS half-extent in units of the local scale

height at rmax_AU (default 6.0).

sma_AU: jaxtyping.Array#
alpha_in: jaxtyping.Array#
alpha_out: jaxtyping.Array#
ksi0_AU: jaxtyping.Array#
gamma: jaxtyping.Array#
beta: jaxtyping.Array#
rmin_AU: jaxtyping.Array#
rmax_AU: jaxtyping.Array#
wavelengths_nm: jaxtyping.Array#
g_HG_grid: jaxtyping.Array#
Ag_grid: jaxtyping.Array#
nx: int#
ny: int#
pixel_scale_arcsec: float#
dist_pc: float#
n_slices_los: int#
n_scale_heights: float#
_zmax_AU()[source]#

LOS half-extent in disk-frame z, evaluated at rmax_AU.

For a flared disk, the scale height grows with radius, so the LOS depth that captures the vertical tails at the outer edge is larger than n_scale_heights * ksi0_AU at sma_AU.

Return type:

jaxtyping.Array

surface_brightness(wavelength_nm, time_jd, incl_deg, pa_deg)[source]#

Render the Augereau 1999 scattered-light disk on a sky-plane grid.

wavelength_nm selects g_HG and Ag via cubic-spline interpolation over wavelengths_nm / g_HG_grid / Ag_grid. Queries outside the grid return NaN. time_jd is part of the AbstractDisk interface but ignored (static disk).

Parameters:

  • wavelength_nm (jaxtyping.Array)

  • time_jd (jaxtyping.Array)

  • incl_deg (jaxtyping.Array)

  • pa_deg (jaxtyping.Array)

Return type:

jaxtyping.Array

spatial_extent()[source]#

Return (width_arcsec, height_arcsec).

Return type:

tuple[float, float]

__repr__()[source]#

Compact summary of radial/vertical/HG parameters + image/Ag grid.

Return type:

str