Detection of Radial Surface Brightness Fluctuations and Color Gradients in Elliptical Galaxies with the Advanced Camera for Surveys

Abstract

We study surface brightness fluctuations (SBFs) in a sample of eight elliptical galaxies using the Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) data drawn from the Hubble Space Telescope archive. SBF magnitudes in the F814W bandpass and galaxy colors from F814W, F435W, and F606W images, when available, are presented. Galaxy surface brightness profiles are determined as well. We present the first SBF-broadband color calibration for the ACS WFC F814W bandpass and (relative) distance moduli estimates for seven of our galaxies. We detect and study in detail the SBF variations within individual galaxies as a probe of possible changes in the underlying stellar populations. Inspecting both the SBF and color gradients in comparison to model predictions, we argue that SBFs and SBF gradients can in principle be used for unraveling the different evolutionary paths taken by galaxies, although a more comprehensive study of this issue would be required. We confirm that the radial variation of galaxy stellar population properties is mainly connected to the presence of radial chemical abundance gradients, with the outer galaxy regions being more metal-poor than the inner ones. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with programs 9427, 9293, and 9399.