| Abstract | Anomalously high K-band surface brightness fluctuations (SBF) have been reported in NGC 4489 by Pahre & Mould (\cite{pah94}), Jensen et al. (\cite{jen96}) and Jensen et al. (\cite{jen98}). However, these conclusions were uncertain because of relatively low signal-to-noise data. New high signal-to-noise data for NGC 4489 have been obtained at the NOAO/KPNO 2.1 m and the ESO/La Silla 3.5 m NTT telescopes. Adopting the I-band SBF distance modulus determined by Tonry et al. (\cite{ton00b}) and the /line MI versus (V-I) calibration of Tonry et al. (\cite{ton00a}), a value of /line MK =-6.29+/-0.10 mag was derived. Relative to the average empirical /line MK derived for giant ellipticals by Jensen et al. (\cite{jen98}) (/line MK= -5.61+/-0.12 mag), the detection of an anomalous K-band SBF in NGC 4489 is confirmed at the two sigma level. Such anomalous fluctuations could be caused by an extended giant branch, consisting of either intermediate-age AGB stars above the tip of the first-ascent giant branch or high-metallicity first-ascent giants, or by lack of a full understanding of the K-band SBF calibration. This result raises questions about the accuracy of K-band SBF distance measurements for elliptical galaxies with unknown stellar composition and underscores the need for /line MK measurements over a larger range of color and luminosity. Based on observations performed at the European Southern Observatory, La Silla, Chile; ESO program No. 62.N-0876. |
