EMU/GAMA: Understanding the link between dust geometry and star formation rate in galaxies

We investigate the link between dust obscuration and star formation rate (SFR) estimators using Hα luminosities, LHα and radio luminosities, Lradio. While the Balmer Decrement (BD) is the standard tool for attenuating Hα, it can fail to account for optically thick dust regions from which Hα cannot escape. The ratio of SFRs estimated from radio luminosity and LHα corrected for dust attenuation using the BD can be used as a probe of the degree of optically thick dust affecting Hα. We explore this combining Evolutionary Map of the Universe (EMU) Early Science data at 887.5 MHz in the Galaxy and Mass Assembly (GAMA) G23 field with the GAMA data. We draw on dust estimates using both the BD and the dust mass, Md, demonstrating systematic underlying dependencies with Lradio/LHα. By combining the BD and Md, we quantify how they relate to Lradio/LHα and other galaxy properties. We use this approach to establish an Hα SFR (SFRHα) estimator that accounts for optically thick dust, demonstrating its consistency with conventional SFR indicators. Rather than proposing a replacement for standard correction methods, we aim to demonstrate the effectiveness of a dust geometry model that integrates both BD and Md parameters. This Hdust parameter provides a more physically complete representation of optically thick environments that traditional methods may overlook, and can produce SFR estimates consistent with traditional techniques.