skyscapes.disk.exovista_parametric

skyscapes.disk.exovista_parametric#

ExovistaParametricDisk: Simplified JAX forward model of ExoVista’s disk model.

Reproduces the per-component disk-density formula from ExoVista’s C++ Image::disk_imager (the kernel underlying distribute_diskpoints) deterministically using the LOS-around-midplane kernel shared with GraterDisk. Multi-component scenes (warm + cold + halo, etc.) are built via CompositeDisk.

What’s reproduced (Stark 2022 / Image.cpp):

  • Vertical Gaussian with constant opening angle hor and per-radius normalization (mass per unit r preserved).

  • Four-region radial profile:

    r > r0+dr: exp(-0.5) * (r/(r0+dr))^-1.5 (outer halo) |r-r0|<dr: exp(-0.5 (r-r0)^2 / dr^2) (Gaussian ring) r0-dr>r>0: inward decay from Wyatt 1999, eq 3.36,

    exp(-0.5) / (1 + 4 eta (1 - sqrt(r/(r0-dr))))

    r <= rinner: additional (r/rinner)^3 cubic ramp

  • Three-component Henyey-Greenstein phase function sum_i(w_i * HG(g_i)), with scalar (g_i, w_i) parameters.

  • nzodis density scaling (zodi units).

  • 1/r^2 stellar illumination dilution (applied by the LOS kernel via division by the squared distance to the star).

What’s intentionally simplified vs the full ExoVista pipeline:

  • No Dohnanyi grain-size integration weighted by Qsca(s, lambda). Wavelength dependence is parameterized phenomenologically through Ag_grid instead.

  • No sublimation cutoff T < T_sublimate (would need stellar Teff and rstar).

  • No stellar-surface-radius cutoff r > r_star.

  • eta is treated as a single grain-size-averaged value, not a per-size quantity (the Image.cpp tempeta = eta * rdust/rblow produces a color gradient absent here).

The class is intentionally faithful to the ExoVista parameterization (r0_AU, dror, rinner_AU, hor, nzodis, eta, three HG (g_i, w_i)) rather than a smaller user-friendly subset. CompositeDisk is the right way to build full multi-component scenes.

References:

Stark, C. C. 2022, AJ, 163, 105

Classes#

ExovistaParametricDisk

ExoVista-style disk component (faithful per-component reproduction).

Functions#

three_component_hg(cos_phi, g0, g1, g2, w0, w1, w2)

Three-component Henyey-Greenstein phase function.

exovista_density(r, z, *, r0_AU, dror, rinner_AU, hor, ...)

ExoVista per-component disk density (Image.cpp formula).

Module Contents#

skyscapes.disk.exovista_parametric.three_component_hg(cos_phi, g0, g1, g2, w0, w1, w2)[source]#

Three-component Henyey-Greenstein phase function.

pfunc = w0 HG(g0) + w1 HG(g1) + w2 HG(g2). The caller is responsible for choosing weights that sum to 1 (we do not normalize here).

Parameters:

  • cos_phi (jaxtyping.Array)

  • g0 (jaxtyping.Array)

  • g1 (jaxtyping.Array)

  • g2 (jaxtyping.Array)

  • w0 (jaxtyping.Array)

  • w1 (jaxtyping.Array)

  • w2 (jaxtyping.Array)

Return type:

jaxtyping.Array

skyscapes.disk.exovista_parametric.exovista_density(r, z, *, r0_AU, dror, rinner_AU, hor, nzodis, eta)[source]#

ExoVista per-component disk density (Image.cpp formula).

Args:

r: Disk-frame cylindrical radius [AU]. Must be strictly positive. z: Disk-frame height [AU]. r0_AU: Ring center [AU]. dror: Fractional ring width, dr = dror * r0_AU. rinner_AU: Inner truncation radius [AU]. Below this, an additional

(r/rinner)^3 cubic ramp suppresses the density.

hor: Opening angle. The local 1-sigma Gaussian vertical scale at

radius r is h = r * hor.

nzodis: Density normalization (zodi units). eta: Poynting-Robertson drag / collision-timescale ratio for the

inward-decay component.

Returns:

Per-LOS-sample density (relative units), same shape as r and z. The caller multiplies by phase function and divides by squared distance to the star.

Parameters:

  • r (jaxtyping.Array)

  • z (jaxtyping.Array)

  • r0_AU (jaxtyping.Array)

  • dror (jaxtyping.Array)

  • rinner_AU (jaxtyping.Array)

  • hor (jaxtyping.Array)

  • nzodis (jaxtyping.Array)

  • eta (jaxtyping.Array)

Return type:

jaxtyping.Array

class skyscapes.disk.exovista_parametric.ExovistaParametricDisk[source]#

Bases: skyscapes.disk.base.AbstractDisk

ExoVista-style disk component (faithful per-component reproduction).

Attributes (PyTree leaves, fittable):

r0_AU: Ring center radius [AU]. dror: Ring fractional width Delta r / r0 (dimensionless). rinner_AU: Inner truncation radius [AU]; below this the density

is suppressed by (r/rinner_AU)^3. Set to a value smaller than rmin_AU to disable.

hor: Opening angle (Gaussian vertical scale / radius). nzodis: Density normalization in zodi units. eta: PR-drag / collision-timescale ratio at r0 - dr. g0, g1, g2: Three-component HG asymmetry parameters. w0, w1, w2: Three-component HG weights. Should sum to 1; not

enforced.

rmin_AU: LOS-integration inner bound [AU]. rmax_AU: LOS-integration outer bound [AU]. wavelengths_nm: 1-D wavelength grid for Ag_grid. Queries

outside this range return NaN.

Ag_grid: Phenomenological albedo scaling vs wavelength.

Static attributes:

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 scale height at

rmax_AU (default 6.0).

r0_AU: jaxtyping.Array#
dror: jaxtyping.Array#
rinner_AU: jaxtyping.Array#
hor: jaxtyping.Array#
nzodis: jaxtyping.Array#
eta: jaxtyping.Array#
g0: jaxtyping.Array#
g1: jaxtyping.Array#
g2: jaxtyping.Array#
w0: jaxtyping.Array#
w1: jaxtyping.Array#
w2: jaxtyping.Array#
rmin_AU: jaxtyping.Array#
rmax_AU: jaxtyping.Array#
wavelengths_nm: 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 the ring center.

For ExoVista-style disks the mass is concentrated near r0_AU (ring + nearby halo + inward profile), and the radial profile decays as r^-1.5 outside. Using r0_AU rather than the LOS-bound rmax_AU gives an LOS extent matched to where the density actually lives, so per-slice dz scales with the scale height at the ring rather than with the (much larger) LOS-bound.

Return type:

jaxtyping.Array

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

Render the ExoVista-style disk on a sky-plane grid.

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 ring/density/HG parameters + image/Ag grid.

Return type:

str