Simulations of Dust in Interacting Galaxies. I. Dust Attenuation

A new Monte-Carlo radiative-transfer code, Sunrise, is used in conjunctionwith hydrodynamic simulations of major galaxy mergers to calculate the effectsof dust in such systems. The simulations are in good agreement withobservations of dust absorption in starburst galaxies, and the dust has aprofound effect on their appearance. The dust attenuation increases withluminosity such that at peak luminosities ~90% of the bolometric luminosity isabsorbed by dust. In general, the detailed appearance of the merging eventdepends on the stage of the merger and the geometry of the encounter. Thefraction of bolometric energy absorbed by the dust, however, is a robustquantity that can be predicted from the intrinsic properties bolometricluminosity, baryonic mass, star-formation rate, and metallicity of the system.This paper presents fitting formulae, valid over a wide range of masses andmetallicities, from which the absorbed fraction of luminosity (and consequentlyalso the infrared dust luminosity) can be predicted. The attenuation of theluminosity at specific wavelengths can also be predicted, albeit with a largerscatter due to the variation with viewing angle. These formulae for dustattenuation appear to be valid for both isolated and interacting galaxies, areconsistent with earlier studies, and would be suitable for inclusion intheoretical models, e.g. semi-analytic models of galaxy formation.Comment: 12 pages, 10 figures, submitted to Ap