Radiative transfer in disc galaxies -- III. The observed kinematics of dusty disc galaxies

Abstract

We present SKIRT (Stellar Kinematics Including Radiative Transfer), a new Monte Carlo radiative transfer code that allows the calculation of the observed stellar kinematics of a dusty galaxy. The code incorporates the effects of both absorption and scattering by interstellar dust grains, and calculates the Doppler shift of the emerging radiation exactly by taking into account the velocities of the emitting stars and the individual scattering dust grains. The code supports arbitrary distributions of dust through a cellular approach, whereby the integration through the dust is optimized by means of a novel efficient trilinear interpolation technique.We apply our modelling technique to calculate the observed kinematics of realistic models for dusty disc galaxies. We find that the effects of dust on the mean projected velocity and projected velocity dispersion are severe for edge-on galaxies. For galaxies which deviate more than a few degrees from exactly edge-on, the effects are already strongly reduced. As a consequence, dust attenuation cannot serve as a possible way to reconcile the discrepancy between the observed shallow slopes of the inner rotation curves of low surface brightness galaxies and the predictions of cold dark matter cosmological models. For face-on galaxies, the velocity dispersion increases with increasing dust mass owing to scattering, but the effects are limited, even for extended dust distributions. Finally, we show that serious errors can be made when the individual velocities of the dust grains are neglected in the calculations.

TheHerschelVirgo Cluster Survey

“…We first determined a representative dust temperature using the assumption that the dust is in thermal equilibrium with the interstellar radiation field. We used the Monte Carlo code SKIRT, which was initially developed to investigate the effects of dust extinction on the photometry and kinematics of galaxies (Baes et al 2003), but evolved into a flexible tool that can model the absorption, scattering, and thermal emission of circumstellar discs and dusty galaxies (e.g Vidal & Baes 2007;Baes et al 2010). The stellar body of each galaxy was represented as an exponential profile, with parameters taken from the Goldmine database.…”

Hierarchical octree andk-d tree grids for 3D radiative transfer simulations

“…The goal of this paper is to investigate these issues using the 3D Monte Carlo dust radiative transfer code SKIRT (Baes et al 2003(Baes et al , 2011) and a set of challenging 3D test models. While our tests are performed within the specific framework of the Monte Carlo technique applied to continuum radiative transfer in dusty systems, the results and conclusions should be generally applicable to most if not all radiative transfer simulation codes.…”

FitSKIRT: genetic algorithms to automatically fit dusty galaxies with a Monte Carlo radiative transfer code

“…Fortunately, several powerful 3D radiative transfer A&A 550, A74 (2013) codes with these characteristics have recently been developed (e.g. Gordon et al 2001;Baes et al 2003Jonsson 2006;Bianchi 2008;Robitaille 2011).…”