VOIIVHII_lookupTable

This is a 6D lookup table computed by HIILines (https://github.com/Sheng-Qi-Yang/HIILines). It takes the HII region gas density, metallicity, temperature, and the incident spectrum. It provides OIII/HII region volume ratios and OII/HII region volume ratios that can be used to post-process ISM emission line signals for high-resolution simulations.

The 'age' field lists an array of stellar population age grid in unit of Gyr.

The 'metallicity' field lists an array of log_10 (Z_*) grid. Here Z_* is the stellar metallicity in unit of solar metallicity.

'age' and 'metallicity' fields determines the shape of stellar radiation spectra, provided by FSPS lookup table (https://zenodo.org/record/6338462 SSP_Spectra_Conroy-et-al_v2.5_imfChabrier.hdf5) 

The 'logQ' field lists an array of log_10(Q_HI) grid. Here Q_HI is the hydrogen ionization photon generation rate of the stellar population in unit of s^-1. This field determines the amplitude of the stellar radiation spectra.

The 'lognH' field lists an array of log_10(n_H) grid. Here n_H is the HII region gas density in unit of cm^-3.

The 'logZ' field lists an array of log_10(Z_gas) grid. Here  Z_gas is the HII region gas-phase metallicity in unit of solar metallicity.

The 'T4' field lists an array of T/10000 K grid. Here T is the HII region gas temperature in unit of K.

The 'VOII2VHII' and 'VOIII2VHII' fields provides a 6D lookup table of OIII and OII volume correction factors given the above 6 parameters. As an example, a VOII/VHII function can be defined as:

VOII2VHIIf     = scipy.interpolate.RegularGridInterpolator((logQGrid,lognHGrid,logZismGrid,T4Grid,logZstarGrid,ageGrid),VOII2VHII)