Dust attenuation laws of the SINGS/KINGFISH galaxies using Swift/UVOT

We study the variety of dust attenuation laws in the SINGS/KINGFISH galaxies derived via spectral energy distribution (SED) fitting, incorporating new NUV observations from the Swift UV/Optical Telescope (UVOT). The addition of Swift/UVOT integrated light photometry to archival multi-wavelength data improves our ability to determine the slope of the attenuation law and the strength of the 2175 Å dust bump. Due to the degeneracy between dust and the age of the underlying stellar population, we perform SED fitting using three different star formation history (SFH) parameterizations: a decaying exponential, double power law, and nonparametric piecewise function. We find that the slope of the average attenuation law can vary depending on SFH used. Additionally, we find that fits with UVOT data result in systematically lower bump strengths compared to fits with GALEX alone, demonstrating the utility of UVOT data in determining dust attenuation laws in the local universe. We argue for the use of the nonparametric piecewise SFH as it does not impose a rigid shape like parametric methods. Future work is needed on a larger sample to study population level trends and to account for any selection bias effects.