Young, UV-bright Stars Dominate Dust Heating in Star Forming Galaxies

TL;DR

This study demonstrates that in star forming galaxies, young UV-bright stars are the primary source of dust heating, significantly influencing the infrared emission, as shown through observations and radiative transfer modeling.

Contribution

The paper provides evidence that young stellar populations dominate dust heating in star forming galaxies, using Spitzer data and a new radiative transfer model.

Findings

Young stars contribute over 80% of far-IR luminosity.

Old stellar populations contribute less than 20% to dust heating.

Young stellar populations are the main drivers of dust emission in star forming galaxies.

Abstract

In star forming galaxies, dust plays a significant role in shaping the ultraviolet (UV) through infrared (IR) spectrum. Dust attenuates the radiation from stars, and re-radiates the energy through equilibrium and non-equilibrium emission. Polycyclic aromatic hydrocarbons (PAH), graphite, and silicates contribute to different features in the spectral energy distribution; however, they are all highly opaque in the same spectral region - the UV. Compared to old stellar populations, young populations release a higher fraction of their total luminosity in the UV, making them a good source of the energetic UV photons that can power dust emission. However, given their relative abundance, the question of whether young or old stellar populations provide most of these photons that power the infrared emission is an interesting question. Using three samples of galaxies observed with the Spitzer Space Telescope and our dusty radiative transfer model, we find that young stellar populations (on the order of 100 million years old) dominate the dust heating in star forming galaxies, and old stellar populations (13 billion years old) generally contribute less than 20% of the far-IR luminosity.