Dust Attenuation in Hydrodynamic Simulations of Spiral Galaxies

Abstract

We study the effects of dust in hydrodynamic simulations of spiral galaxies when different radial metallicity gradients are assumed. SUNRISE, a Monte-Carlo radiative-transfer code, is used to make detailed calculations of the internal extinction of disk galaxies caused by their dust content. SUNRISE is used on eight different Smooth Particle Hydrodynamics (SPH) simulations of isolated spiral galaxies. These galaxies vary mainly in mass and hence luminosity, spanning a range in luminosities from -16 to -22 magnitudes in the B band. We focus on the attenuation in different wavelength bands as a function of the disk inclination and the luminosity of the models, and compare this to observations. Observations suggest different metallicity gradients for galaxies of different luminosities. These metallicity gradients were explored in our different models, finding that the resulting dust attenuation matches observations for edge-on galaxies, but do not show a linear behaviour in log axis ratio as some observations have suggested. A quadratic law describing the dependence of attenuation on inclination, as proposed by more recent observations, reconciles the attenuation of the simulations at intermediate inclinations with observations. We also compare the total infrared-to-ultraviolet flux ratios for the simulated galaxies with those of the SINGS sample and find general agreement. Finally we compare our results with those from simpler models that do not take into account structure such as spiral arms, finding that the inclusion of sub-structure on the size scale of spiral arms does not change conclusions about the attenuation dependence on inclination or wavelength.

12 pages, 8 figures, all figures require colors, accepted for publication in MNRAS. Major changes from v1 include: Comparison of the calculated infrared-to-ultraviolet ratios in our models to those observed by SIGNS, clearer fonts in our plots and clearer justification of the rationale behind the adopted gradients. Changes from v2: Added journal-ref

References in corpus (4)

• The effect of galaxy mass ratio on merger--driven starbursts
• An Ultraviolet-to-Radio Broadband Spectral Atlas of Nearby Galaxies
• Sunrise: Polychromatic Dust Radiative Transfer in Arbitrary Geometries
• Modelling the spectral energy distribution of galaxies. IV Correcting apparent disk scalelengths and central surface brightnesses for the effect of dust at optical and near-infrared wavelengths

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• Inclination-Dependent Extinction Effects in Disk Galaxies in the Sloan Digital Sky Survey
• Evaluating and Improving Semi-analytic modelling of Dust in Galaxies based on Radiative Transfer Calculations
• Color Distributions, Number and Mass Densities of Massive Galaxies at 1.5 < z < 3: Comparing Observations with Merger Simulations