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Session 75 - Dust & PAHs in Galaxies.
Display session, Friday, January 09
We present a series of numerical simulations for radiative transfer of disk galaxies with clumpy dust distribution. Previous models of radiative transfer for spiral galaxies usually assumed smooth distribution of stars and dust. In our models, we considered different distributions of dust, i.e. dust clouds of different sizes in different numbers, while maintaining the same total amount of dust content. In each simulation, we have computed dust absorption in three passbands; B, V and I. Standard galaxy surface photometry techniques have been applied to numerical model galaxies. From our analysis, we conclude that the internal extinction effects, such as total extinction and color excess, depend strongly on clumpy nature of dust distribution. The apparent extinction significance is dominated by the volume filling factor of dust. If the filling factor is very small (\leq0.1), the extinction by dust is negligible except at high inclination (i\geq70^\circ). When the filling factor increases to \sim0.2, the extinction by clumpy dust becomes significant; we can use a smooth dust distribution to imitate the effect only if the inclination is very high so that the clumpiness effect is averaged out. The clumpy nature of dust can seriously affect the estimate of the dust opacity of galaxies. In order to investigate the dust content and opacity with more accuracy, we will need to understand more about dust filling factor in spiral galaxies by further observations.
Program listing for Friday