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Published April 10, 1999 | Submitted + Published
Journal Article Open

Detection of surface brightness fluctuations in NGC 4373 using the Hubble Space Telescope


Surface brightness fluctuations (SBF) have been detected for three elliptical galaxies-NGC 3379 in the Leo group, NGC 4406 in the Virgo cluster, and NGC 4373 in the Hydra-Centaurus supercluster-using marginally sampled, deep images taken with the Planetary Camera of the WFPC2 instrument on the Hubble Space Telescope (HST). The power spectrum of the fluctuations image is well fitted by an empirical model of the point-spread function constructed using point sources identified in the held. Comparison with high-quality ground-based observations of all three galaxies show excellent agreement in the measurement of the distance modulus over a substantial range in distance. This demonstrates the capability of the Planetary Camera of WFPC2 to measure distances using the SBF technique despite the marginal sampling and small spatial coverage of the images. The residual variance due to unresolved sources in all three galaxies is only 2%-5% of the detected fluctuations signal, which confirms the advantage of HST imaging in minimizing the uncertainty of this SBF correction. Extensive consistency checks, including an independent SBF analysis using an alternate software package, suggest that our internal uncertainties are <0.02 mag. The fluctuations magnitude for NGC 4373 is /_(F814W) = 31.31±0.05 mag, corresponding to a distance modulus of (m-M)_0 = 32.99±0.11. This implies a peculiar velocity for this galaxy of 415±330 km s^(-1), which is smaller than derived from the D_n-σ relation.

Additional Information

© 1999 American Astronomical Society. Received 1997 November 25; accepted 1998 November 12. We acknowledge many helpful discussions with J. Blakeslee and G. Worthey, and the insightful comments and careful reading of the manuscript by the referee, J. Tonry. This work was supported by NASA grant NAS7-1260 to the WFPC2 IDT. M. A. P. received partial support from NSF grant AST-9157412 and Hubble Fellowship grant HF-01099.01-97A from STScI (which is operated by AURA under NASA contract).

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