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Session 10 - Spiral Galaxies.
Display session, Monday, June 10
Great Hall,
In order to investigate the effects of internal extinction in spiral galaxies, we have carried out surface photometry using BRI broadband images of 36 Sc spirals. We expand upon the I-band study of Giovanelli et al. (1994) by applying the same type of analysis to our smaller set of galaxies with multicolor data. We use the images to derive radial brightness profiles in all three colors, and then derive disk structural parameters (such as scale length and central surface brightness) as well as radial color curves. We investigate the relationship between disk inclination and total internal extinction for each of the colors observed, and show that it is consistent with the model presented by Giovanelli et al., which predicts a substantial optical depth in the center of spiral disks, but relative transparency beyond roughly 3 disk scale lengths. In addition, we compare the predictions of realistic models of dust absorption in disks to our observed radial color curves to constrain the distribution of dust in the disks, and to estimate the central optical depth of the absorption layer.
