Nebular emission and choice of IMF, stellar library

[rrgupta]

Hi. I was reading through the arXiv paper by @nell-byler about implementing nebular continuum and emission into python-fsps and had a question. If I understand correctly, the user can switch on nebular continuum and emission for both the Padova+Geneva isochrones and the MIST isochrones and have the nebular effects be implemented self-consistently for both. However, for other choices (e.g., IMF and stellar libraries) is it true that the nebular effects are only self-consistent for the selection of the Kroupa (2001) IMF and the BaSeL 3.1 spectral library and that changing these will result in inconsistent results?
For example, if I need the higher wavelength resolution of the MILES library and want to include nebular effects, do I need to worry that my nebular fluxes are not really correct? Thanks.

[bd-j]

MILES should be fine since it is only different than BaSeL in the optical (I think) while it is the ionizing spectra that matter for the emission line ratios. But yes, changing the IMF or or anything else beyond stellar metallicity that might affect the ionizing continuum will result in loss of consistency. The degree of this loss depends on the degree of difference in the ionizing stellar continuum.

[bd-j]

Just to clarify a bit, the Hydrogen emission lines will still be largely consistent, since they have only a very weak dependence on the shape of the ionizing spectrum (through a nebular T_e^(1/2) dependence), but scale directly with the number of ionizing photons, which is calculated self-consistently on-the-fly, including IMF effects, etc.

It is only the metal line ratios that might be significantly affected by changes from the assumptions of Byler et al.