Multicolor Photometry of Barred Spiral Galaxies

Extract

B – V and R – I color maps (from CCD imagery obtained at Cerro Tololo Inter-American Observatory) of six barred spiral galaxies have been used (Horst 1992) to investigate stellar populations within the bars and nuclei. Two-color diagrams show that the distribution of pixel colors largely parallels the expected locus for normal unreddened stars. If the “reddening” law is assumed to remain fairly constant, and if the slope of the vector associated with this reddening law is additionally assumed to be commensurate with that derived from models which take into account both absorption and scattering (Witt et al. 1992), one concludes that the overall effects of internal extinction are remarkably uniform along the bars and within the nuclei of all six galaxies. It thus appears reasonable as a first approximation to shift the observed data along the assumed reddening vector to estimate the spectral types of stars that are present and to investigate differences between bar and bulge populations. Nevertheless, to correct surface brightness distributions for the effects of internal extinction, and hence to proceed with more detailed attempts to model the various luminosity components (i. e., the bulge, bar, etc.), is a complex problem which must be addressed through numerical models explicitly designed to reproduced barred systems.