Spectra

Synthesizer enables the generation of multiple different spectra which are associated with galaxies (Galaxy objects) or their components. The flowchart below shows how these different spectra are generated by different components. Full details on each component are provided below.

Flowchart showing the different spectra generation components in synthesizer

Components

  • incident spectra are the spectra that serve as an input to the photoionisation modelling. In the context of stellar population synthesis these are the spectra that are produced by these codes and equivalent to the “pure stellar” spectra.

  • transmitted spectra is the incident spectra that is transmitted through the gas in the photoionisation modelling. Functionally the main difference between transmitted and incident is that the transmitted has little flux below the Lyman-limit, since this has been absorbed by the gas. This depends on fesc.

  • nebular is the nebular continuum and line emission predicted by the photoionisation model. This depends on fesc.

  • reprocessed is the emission which has been reprocessed by the gas. This is the sum of nebular and transmitted emission.

  • escaped is the incident emission that escapes reprocessing by gas. This is fesc * incident. This is not subsequently affected by dust.

  • intrinsic is the sum of the escaped and reprocessed emission, essentially the emission before dust attenuated.

  • attenuated is the reprocessed emission with attenuation by dust.

  • emergent is the combined emission including dust attenuation and is the sum of reprocessed_attenuated and escaped. NOTE: this does not include thermal dust emission, so is only valid from the UV to near-IR.

  • dust is the thermal dust emission calculated using an energy balance approach, and assuming a dust emission model.

  • total is the sum of attenuated and dust, i.e. it includes both the effect of dust attenuation and dust emission.

  • For two component dust models (e.g. Charlot & Fall 2000) we also generate the individual spectra of the young and old component. This includes young_incident, young_nebular, young_attenuated etc. young and old are equivalent to total for the young and old components.