CERIDWEN Stellar Population Grids: Standard SSPs, BPASS, and Alpha Enhancement

Stellar population synthesis grids ssp_data_mist_miles.h5 FSPS v3.2 grid generated with python-fsps v0.4.7 using MIST isochrones, MILES spectra, and a Chabrier (2003) IMF. Property Value Isochrones MIST Spectral library MILES IMF Chabrier (2003), imf_type = 1 FSPS version 0.5.0 Schema version 1.0 Build arguments {'imf_type': 1} Metallicity grid 13 points in log10(Z), spanning [-4.233, -1.233] Age grid 107 points in log10(age/Gyr), spanning [-4.000, +1.300] Age range 0.0001-20 Gyr Wavelength grid 5,994 points spanning 91-100,000,000 Angstrom Flux-array shape (13, 107, 5994) Axis order (n_met, n_age, n_wave) Flux units L_sun Hz^-1 M_sun^-1 Data type float64 Approximate size 63.6 MB Library resolution sigma_v [43.7, 8937.9] km/s over [91, 100000000] AA (100% of pixels; NaN elsewhere) Resolution source grid 2-pixel sampling floor derived from ssp_wave (sigma_v = 0.8493 c dlambda/lambda); element-wise max with library LSF: MILES FWHM 2.54A (Falcon-Barroso et al. 2011, A&A 532, A95) The metallicity values represent the absolute metallicity mass fraction, Z, rather than Z/Z_sun. ssp_data_bpass.h5 Grid generated from the pre-integrated BPASS v2.x simple stellar population models. The IMF and binary stellar-evolution assumptions are fixed by the BPASS SSP tables. Property Value Isochrone type bpss Spectral library bpass Recorded FSPS parameters {'imf_type': 1} FSPS version 0.4.9.dev16+gc18b87021 Schema version 1.0 Metallicity grid 12 points in log10(Z), spanning [-4.000, -1.398] Age grid 43 points in log10(age/Gyr), spanning [-3.000, +1.200] Age range 0.001-15.8 Gyr Wavelength grid 15,000 points spanning 1-100,000,000 Angstrom Flux-array shape (12, 43, 15000) Axis order (n_met, n_age, n_wave) Flux units L_sun Hz^-1 M_sun^-1 Data type float64 Approximate size 59.1 MB Library resolution sigma_v [25.5, 279736.0] km/s over [1, 100000000] AA (100% of pixels; NaN elsewhere) Resolution source grid 2-pixel sampling floor derived from ssp_wave (sigma_v = 0.8493 c dlambda/lambda) The metallicity values represent the absolute metallicity mass fraction, Z, rather than Z/Z_sun. amist_c3k_hr_krou_afe.h5 - high resolution FSPS-compatible alpha-enhanced SSP grid generated from MIST v2.5 isochrones and the high-resolution C3K v2.3 spectral library. Property Value Isochrones MIST v2.5 (aMIST, alpha-variable) Spectral library C3K v2.3 high resolution (c3k_hr, vt = 10 km/s) IMF Kroupa, imf_type = 2 FSPS version — Schema version 2.0 Source file ssp_final_mistv2.5_c3kv2.3vt10allfal_250722.fits Provider M. J. Park (2025-07-22) Solar metallicity reference Z_sun = 0.0185 [Fe/H] to log Z conversion log10(Z) = [Fe/H] + log10(Z_sun) Recorded wavelength limits 100.0-99,595,854.863 Angstrom [alpha/Fe] grid 5 points: [-0.2, 0.0, 0.2, 0.4, 0.6] Metallicity grid 13 points in log10(Z), spanning [-4.233, -1.233] Age grid 107 points in log10(age/Gyr), spanning [-4.000, +1.300] Age range 0.0001-20 Gyr Wavelength grid 10,992 points spanning 100.0-99,595,854.9 Angstrom Flux-array shape (5, 13, 107, 10992) Axis order (n_afe, n_met, n_age, n_wave) Flux units L_sun Hz^-1 M_sun^-1 Data type float64 Approximate size 583.3 MB Library resolution sigma_v [23.2, 2546.3] km/s over [100, 99595855] AA (100% of pixels; NaN elsewhere) Resolution source grid 2-pixel sampling floor derived from ssp_wave (sigma_v = 0.8493 c dlambda/lambda) The metallicity values represent the absolute total metallicity mass fraction, Z, rather than Z/Z_sun or [Fe/H].