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Session 40 - Starburst Galaxies.
Display session, Wednesday, June 11
South Main Hall,
We present the results of a study aimed at establishing the properties of the host galaxies of blue compact dwarfs (BCDs). These galaxies represent the most extreme cases of active star-formation in low-luminosity systems (M_B of -12 to -17). Surface brightness fitting routines were applied to deep CCD images to produce radial brightness profiles for 17 BCDs and 11 non-active dwarf irregular galaxies. From these we derive scale lengths, central surface brightnesses, and an estimate of the starbursts' contribution to the total galaxian light. Our fitting technique avoided (as much as possible) the light from the BCD starburst itself, and therefore allows us to make a direct comparison between the structural parameters of the BCDs and the dIs.
We find that the BCDs exhibit exponential profiles at large radii, outside of the starburst regions. However, the extrapolated central surface brightness of the exponential component of the BCDs (which does not include the light from the starburst) tends to be systematically higher than corresponding values for the dwarf irregulars. This suggests that the BCDs may be hosted preferentially by galaxies with higher central mass densities. The BCDs also have smaller scale lengths than dIs of the same luminosity. This difference persists even after correcting for the luminosity enhancement of the BCDs, again suggesting that BCDs may not be hosted by typical dI galaxies. In fact, several of the BCDs appear to consist of starbursts located in dwarf elliptical galaxies. We comment on how these results may constrain proposed evolutionary scenarios for dwarf galaxies.
Program listing for Wednesday