Characterizing Dust Attenuation in Local Star Forming Galaxies: UV and Optical Reddening

TL;DR

This study analyzes dust attenuation in approximately 10,000 local star-forming galaxies using UV and optical data, revealing a generally consistent attenuation curve with notable scatter and correlations with galaxy properties.

Contribution

It provides a new characterization of dust attenuation curves in local galaxies, including the first derivation of a single effective curve applicable to most galaxies and insights into its relation with galaxy properties.

Findings

Derived a universal attenuation curve with lower UV attenuation than previous models.

Found no significant 2175Å feature in the average attenuation curve.

Identified correlations between dust reddening and galaxy metallicity, mass, and SFR.

Abstract

The dust attenuation for a sample of $\sim$10000 local ($z\lesssim0.1$) star forming galaxies is constrained as a function of their physical properties. We utilize aperture-matched multi-wavelength data available from the Galaxy Evolution Explorer (GALEX) and the Sloan Digital Sky Survey (SDSS) to ensure that regions of comparable size in each galaxy are being analyzed. We follow the method of Calzetti et al. (1994) and characterize the dust attenuation through the UV power-law index, $\beta$, and the dust optical depth, which is quantified using the difference in Balmer emission line optical depth, $\tau_B^l=\tau_{\mathrm{H}\beta} - \tau_{\mathrm{H}\alpha}$. The observed linear relationship between $\beta$ and $\tau_B^l$ is similar to the local starburst relation, but the large scatter ($\sigma_{\mathrm{int}}=0.44$) suggests there is significant variation in the local Universe. We derive a selective attenuation curve over the range $1250\mathrm{\AA}<\lambda<8320\mathrm{\AA}$ and find that a single attenuation curve is effective for characterizing the majority of galaxies in our sample. This curve has a slightly lower selective attenuation in the UV compared to previously determined curves. We do not see evidence to suggest that a 2175\AA\ feature is significant in the average attenuation curve. Significant positive correlations are seen between the amount of UV and optical reddening and galaxy metallicity, mass, star formation rate (SFR), and SFR surface density. This provides a potential tool for gauging attenuation where the stellar population is unresolved, such as at high-$z$.