Affected Repositories

• PyAutoGalaxy (primary)
• PyAutoLens
• autolens_workspace

Branch Survey

Suggested branch: feature/magnification-maps-image-plane

Implementation Steps

1. PyAutoGalaxy, autogalaxy/galaxy/plot/galaxies_plots.py (or a sibling module): plot_magnification_2d(mass_obj, grid, contour_levels=(2, 5, 10, 20, 50, 100), include_critical_curves=True, vmax=None, title=..., output_path=..., output_format=..., ax=None).
   • μ from LensCalc.from_mass_obj(mass_obj).magnification_2d_from(grid=grid).
   • Plot log10|μ| via plot_array(ax=...) with the colour range capped (default from percentiles, so the divergences near the critical lines don't set it).
   • Draw ax.contour at log10 of the chosen μ levels on the native grid, with labels.
   • Overlay critical curves from _critical_curves_from(mass_obj, grid) through the existing lines= route.
2. Export from autogalaxy/plot/__init__.py.
3. Tests in test_autogalaxy/galaxy/plot/: renders to file, with and without contours and critical curves, single isothermal galaxy.
4. PyAutoLens: export from autolens/plot/__init__.py; test with a two-plane Tracer.
5. autolens_workspace: replace the manual aplt.plot_array(magnification) in scripts/guides/lens_calc.py; add the map to scripts/imaging/source_science.py; run regenerate_navigator.py autolens; smoke both scripts.

Key Files

• autogalaxy/galaxy/plot/galaxies_plots.py — new function
• autogalaxy/util/plot_utils.py — plot_array, _critical_curves_from
• autogalaxy/operate/lens_calc.py — magnification_2d_from
• autolens/plot/__init__.py — aplt export
• autolens_workspace/scripts/guides/lens_calc.py, scripts/imaging/source_science.py

Magnification maps 8a: image-plane log|mu| map with constant-mu contours and critical curves

Type: feature
Target: PyAutoGalaxy
Repos:

• PyAutoGalaxy
• PyAutoLens
• autolens_workspace
  Themes:
• visualization
• cluster
  Epic: cluster-strong-lensing
  Phase: 8a
  Parent: draft/feature/autolens/magnification_maps_visualization.md
  Difficulty: medium
  Autonomy: supervised
  Priority: high
  Status: formalised
  Consequence: judge
  Review-minutes: 25
  Unattended: no
  Filed: 2026-11-02

Original request (human, 2026-11-02)

yes go ahead with 8a

(Slice of phase 8 magnification_maps_visualization.md, sliced 8a→8d after a 2026-11-02 re-audit.)

Re-audit (2026-11-02)

• The image-plane magnification is only the 9th panel of subplot_fit in fit_imaging_plots.py (~l.730/789) and
  fit_interferometer_plots.py (~l.612/685), on a LINEAR colour scale; no standalone plot function; no aplt export.
• plot_array(contours=int) (autoarray/plot/array.py, _apply_contours in autoarray/plot/utils.py:849) takes a level
  COUNT only — no explicit mu levels.
• Critical curves: _critical_curves_from(mass_obj, grid) in autogalaxy/util/plot_utils.py:492.
• guides/lens_calc.py (~l.318) plots magnification manually with aplt.plot_array.

Work

1. (Dropped 2026-11-02: PyAutoArray is claimed by rectangular-gradient-rtu-sparse; no PyAutoArray change —
   plot_array takes ax, so the explicit-level contours are drawn on that axes inside the PyAutoGalaxy function.)
2. PyAutoGalaxy: plot_magnification_2d(mass_obj, grid, ...) — log10|mu| image-plane map, colour range capped near the
   critical lines, constant-mu contours (default 2, 5, 10, 20, 50, 100), optional critical-curve overlay; works for any
   mass object (Galaxies, Tracer); exported from autogalaxy.plot. Unit tests.
3. PyAutoLens: export via aplt; Tracer test (incl. multi-plane).
4. autolens_workspace: use it in guides/lens_calc.py and imaging/source_science.py; regenerate the navigator
   catalogue (regenerate_navigator.py autolens); smoke.

Witness: aplt.plot_magnification_2d(tracer, grid) renders log|mu| with labelled constant-mu contours and critical
curves for the imaging simple__no_lens_light lens and a multi_galaxy lens; library tests pass; workspace scripts
smoke clean.