Dust reddening in star-forming galaxies

TL;DR

This paper derives empirical relations linking dust reddening in star-forming galaxies to properties like luminosity, metallicity, and inclination, facilitating better modeling of dust effects in galaxy evolution studies.

Contribution

It provides new empirical formulae for dust reddening based on a large SDSS galaxy sample, incorporating multiple galaxy properties for improved accuracy.

Findings

Reddening correlates with Halpha luminosity, surface brightness, metallicity, and inclination.

Edge-on galaxies show more attenuation than face-on at similar intrinsic luminosities.

Empirical relations have a scatter of only 0.07 mag, suitable for modeling purposes.

Abstract

We present empirical relations between the global dust reddening and other physical galaxy properties including the Halpha luminosity, Halpha surface brightness, metallicity and axial ratio for star-forming disc galaxies. The study is based on a large sample of ~22 000 well-defined star-forming galaxies selected from the Sloan Digital Sky Survey (SDSS). The reddening parameterized by color excess E(B-V) is derived from the Balmer decrement. Besides the dependency of reddening on Halpha luminosity / surface brightness and gas phase metallicity, it is also correlated with the galaxy inclination, in the sense that edge-on galaxies are more attenuated than face-on galaxies at a give intrinsic luminosity. In light of these correlations, we present the empirical formulae of E(B-V) as a function of these galaxy properties, with a scatter of only 0.07 mag. The empirical relation can be reproduced if most dust attenuation to the HII region is due to diffuse interstellar dust distributing in a disc thicker than that of HII regions. The empirical formulae can be incorporated into semi-analytical models of galaxy formation and evolution to estimate the dust reddening and enable comparison with observations more practically.