Dust Properties and Star-Formation Rates in Star-Forming Dwarf Galaxies

TL;DR

This study uses Spitzer data to analyze dust properties in star-forming dwarf galaxies, revealing variations in dust composition and their impact on star-formation rate estimates, especially related to metallicity effects.

Contribution

It provides new insights into how dust properties and metallicity influence mid-infrared star-formation rate indicators in dwarf galaxies.

Findings

Dwarf galaxies have more hot dust and smaller grains compared to larger galaxies.

PAH emission decreases with metallicity in these galaxies.

Star-formation rate estimates vary significantly due to ISM property differences.

Abstract

We have used the Spitzer Space Telescope to study the dust properties of a sample of star-forming dwarf galaxies. The differences in the mid-infrared spectral energy distributions for these galaxies which, in general, are low metallicity systems, indicate differences in the physical properties, heating, and/or distribution of the dust. Specifically, these galaxies have more hot dust and/or very small grains and less PAH emission than either spiral or higher luminosity starburst galaxies. As has been shown in previous studies, there is a gradual decrease in PAH emission as a function of metallicity. Because much of the energy from star formation in galaxies is re-radiated in the mid-infrared, star-formation rate indicators based on both line and continuum measurements in this wavelength range are coming into more common usage. We show that the variations in the interstellar medium properties of galaxies in our sample, as measured in the mid-infrared, result in over an order of magnitude spread in the computed star-formation rates.