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Session 108 - Cosmology and Distance Indicators.
Oral session, Thursday, January 16
Optical surface brightness fluctuations (SBFs) have been shown to be a remarkably good distance indicator. Because fluctuations are dominated by red giant stars, SBFs are much brighter in the near-IR than at optical wavelengths, and are potentially useful to greater distances. We have applied the SBF technique to K-band images of elliptical galaxies in the local group, Virgo, Fornax, Eridanus, Hydra, and Coma clusters. Galaxies in the nearer clusters were used to calibrate the K-band SBF distance scale across a range of stellar population properties using both Cepheid distances and I-band SBF measurements. We find that the absolute fluctuation magnitude is consistent with theory and other K-band SBF studies, but has a modest dependence on galaxy color that is not yet understood in terms of simple stellar population models. We also find that the fluctuation amplitude measured is sensitive to residual variance resulting from image reduction artifacts or contamination by globular clusters and background galaxies. It is therefore very important to achieve a high S/N ratio to assure consistency.
Program listing for Thursday