Planet Array Generator Scripts

This repository provides two sampling scripts for generating synthetic planet (and low–mass star / brown dwarf) properties useful for microlensing / population studies.

Distributions implemented:

• SUMI2023_draw_planet_arrays.py – Composite Sumi-style mass function: a sum of two independent power-law segments in base-10 logarithmic mass space:

  • Planet (free-floating / wide orbit) component: ( \frac{dN}{d\log{10} M} = Z{\rm planet} \,( M / M{\rm pivot,planet} )^{-\alpha4} ) with published parameters (\alpha4 = 0.96), (Z{\rm planet}=2.18\, \mathrm{dex^{-1}\,star^{-1}}), pivot (M{\rm pivot,planet}=8\,M\oplus), validity approximately 0.33–6660 (M\oplus) (1e-6–0.02 M(\odot)). Integrates to ~21 planets per star over that range.
  • Rising star + brown dwarf (BD) low-mass tail: ( \frac{dN}{d\log{10} M} = A{\rm BD} \,( M / M{\rm pivot,BD} )^{-\alpha3} ) with (\alpha3 = -0.82) (negative ⇒ rises with increasing mass), pivot (M{\rm pivot,BD}=38\,M\oplus). The amplitude (A{\rm BD}) is solved internally from a target number of brown dwarfs per star in a chosen interval (default: 0.2 objects in 0.012–0.08 M(\odot)). Validity adopted: 3×10⁻⁴–0.8 M(\odot) (~100–2.6×10⁵ M(_\oplus)).
  • The total differential frequency is the sum of the two segments wherever they overlap. There is no rejection; sampling uses analytic inverse CDFs and mixture weights from exact integrals.
  • Output includes a component label column (comp): 0 = planet segment, 1 = star/BD segment.

• uniform_draw_planet_arrays.py – Log-uniform baseline: masses drawn log-uniform between 0.1–10,000 M(_\oplus); semi-major axes log-uniform (0.3–30 au); inclinations isotropic; orbital phase uniform.

Requirements

• Python 3.11+ (tested)
• NumPy

Optional (for exploration / plotting): matplotlib, pandas (used in the notebook).

Input

Both scripts read a source file (default: gulls_surot2d_H2023.sources) whose first whitespace–delimited column lists integer field identifiers. For each field, nf files of nl sampled objects are produced (parallelized across CPU cores).

Output

Files are written under planets/<run_name>/ as:

<run_name>.planets.<field_number>.<file_index>

Columns:

• mass (M_Sun) – Mass in solar masses (sampled internally in Earth masses).
• a (au) – Semi–major axis (au, log–uniform between configured bounds).
• inc (deg) – Signed inclination (deg) from an isotropic distribution.
• p (deg) – Orbital phase (deg) uniform in [0, 360).
• comp (0=planet,1=starbd) – (Only in SUMI composite script) segment identifier.

Usage

1. Composite Sumi-style Mass Function

Generates a mixture of the declining planetary power law and the rising star+BD segment; mixture weights are exact integrals over the requested mass interval. Supports deterministic runs via FIXED_BASE_SEED.

bash python SUMI2023_draw_planet_arrays.py

2. Log-Uniform Mass Function

Baseline sampler with purely log-uniform mass distribution (0.1–10,000 M(_\oplus)).

bash python uniform_draw_planet_arrays.py

Customization

Key parameters (edit near top of each script):

• nl – number of objects per output file.
• nf – number of files per field.
• rundes – run descriptor used in output directory & filenames.
• sources_file – path to field list.
• file_ext – set to .npy for NumPy binary output; empty for CSV-like text.
• overwrite_existing – if False existing files are left intact.
• FIXED_BASE_SEED – set an integer for reproducible deterministic sampling across processes.

Composite-only parameters (defaults derived from literature):

• Z_PLANET, ALPHA_PLANET (α4), PIVOT_PLANET.
• A_BD (solved amplitude), ALPHA3, PIVOT_BD.
• Global mass truncation (mmin, mmax) and semi–major axis log bounds (amin, amax).

Notes

• Multiprocessing: a pool sized by mp.cpu_count() is used; each task derives a unique RNG seed when FIXED_BASE_SEED is set.
• Mass sampling in the composite script is analytic (no rejection), ensuring efficiency even for large draws.
• Component labels enable downstream filtering (e.g., isolate planetary segment only).
• The uniform script omits the label column by design.

Example Output

Example composite output header (text mode):

```

mass (M_Sun), a (au), inc (deg), p (deg), comp (0=planet,1=starbd)

```

Example uniform output header:

```

mass (M_Sun), a (au), inc (deg), p (deg)

```

For questions or issues, please contact the script author.