Radiation fields in star-forming galaxies: the disk, thin disk and bulge

TL;DR

This paper presents a library of radiation fields in spiral galaxies derived from stellar radiation transfer models, enabling self-consistent multi-wavelength analysis of galaxy observables and providing analytic solutions for various galaxy components.

Contribution

It introduces a comprehensive library of radiation fields for galaxy components, with analytic solutions and self-consistent integration with spectral energy distributions.

Findings

Radiation fields vary significantly between disks, thin disks, and bulges.

Analytic solutions for optically thin disks are exact, aiding benchmarking.

Bulge radiation fields depend strongly on Sersic index.

Abstract

We provide and describe a library of diffuse stellar radiation fields in spiral galaxies derived using calculations of the transfer of stellar radiation from the main morphological components - disks, thin disks, and bulges - through the dusty interstellar medium. These radiation fields are self-consistent with the solutions for the integrated panchromatic spectral energy distributions (SEDs) previously presented using the same model. Because of this, observables calculated from the radiation fields, such as gamma-ray or radio emission, can be self-consistently combined with the solutions for the ultraviolet/optical/submillimeter SEDs, thus expanding the range of applicability of the radiation transfer model to a broader range of wavelengths and physical quantities. We also give analytic solutions for radiation fields in optically thin stellar disks, in stellar disks with one dust disk and in stellar disks with two dust disks. The analytic solutions for the direct light are exact and can be used as benchmarks. The analytic solutions with scattering are only approximate, becoming exact only in the extreme optically thick limit. We find strongly contrasting solutions for the spatial distribution of the radiation fields for disks, thin disks and bulges. For bulges we find a strong dependence of the radiation fields on Sersic index.