Specialized Template Function phot::PhotConvert< PhotSystem::Flambda, PhotSystem::Fnu >

Function Documentation

template<>
constexpr auto phot::PhotConvert<PhotSystem::Flambda, PhotSystem::Fnu>(const double photIn, const double wl) -> double

Convert Flambda (erg/s/[cm^2/]Angstrom) to Fnu (erg/s/[cm^2/]Hz)

F_nu = F_lambda * lambda^2 / c (with every quantity in cgs units: F_lambda in erg/s/[cm^2/]cm, lambda and c in cm and cm/s respectively, giving F_nu in erg/s/[cm^2/]Hz), rewritten so F_lambda’s own conversion from a per-Angstrom to a per-cm density (dividing by utils::Angstrom) and one of lambda’s two powers’ conversion from Angstrom to cm (multiplying by utils::Angstrom) cancel, leaving a single overall factor of utils::Angstrom. This is purely a change of independent variable (wavelength to frequency), so it applies identically whether photIn carries a per-area factor (a genuine flux) or not (a specific luminosity) – unlike a conversion to a magnitude system, this one never needs to adopt any particular distance, since Fnu (unlike ST/AB/Vega) has no standard distance of its own to adopt in the first place.