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Date and Time of the Query: 2019-05-26 T12:35:49 PDT
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For refcode 2002ApJ...564..216L:
Retrieve 23 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2002ApJ...564..216L Surface Brightness Fluctuations of Fornax Cluster Galaxies: Calibration of Infrared Surface Brightness Fluctuations and Evidence for Recent Star Formation Michael C. Liu and James R. Graham Astronomy Department, University of California, Berkeley, CA 94720; mliu@ifa.hawaii.edu and Stephane Charlot Institut d'Astrophysique de Paris, CNRS, 75014 Paris, France Received 2001 March 14; accepted 2001 September 9 ABSTRACT We have measured K_S_-band (2.0-2.3 microns) surface brightness fluctuations (SBFs) of 19 early-type galaxies in the Fornax Cluster. Fornax is ideally suited both for calibrating SBFs as distance indicators and for using SBFs to probe the unresolved stellar content of early-type galaxies. Combining our results with published data for other nearby clusters, we calibrate K_S_-band SBFs using Hubble Space Telescope (HST) Cepheid cluster distances and I-band SBF distances to individual galaxies. With the latter, the resulting calibration is M^bar^_K_S__ = (-5.84 +/- 0.04) + (3.6 +/- 0.8)[(V - I_c_)_0_ - 1.15], valid for 1.05 < (V - I_c_)_0_ < 1.25 and not including any systematic errors in the HST Cepheid distance scale. The fit accounts for the covariance between V - I_c_ and M^bar^_K_S__ when calibrated in this fashion. The intrinsic cosmic scatter of M^bar^_K_S__ appears to be larger than that of I-band SBFs. S0 galaxies may follow a different relation, although the data are inconclusive. The discovery of correlation between K_S_-band fluctuation magnitudes and colors with V - I_c_ is a new clue into the star formation histories of early-type galaxies. This relation naturally accounts for galaxies previously claimed to have anomalously bright K-band SBFs, namely, M32 and NGC 4489. Models indicate that the stellar populations dominating the SBF signal have a significant range in age; some scatter in metallicity may also be present. The youngest ages imply some galaxies have very luminous giant branches, akin to those in intermediate-age (few Gyr) Magellanic Cloud clusters. The inferred metallicities are roughly solar, although this depends on the choice of theoretical models. A few Fornax galaxies have unusually bright K_S_-band SBFs, perhaps originating from a high-metallicity burst of star formation in the last few Gyr. The increased spread and brightening of the K_S_-band SBFs with bluer V - I_c_ suggest that the lower mass cluster galaxies (<~0.1L*) may have had more extended and more heterogeneous star formation histories than those of the more massive galaxies. Subject headings: distance scale - galaxies: distances and redshifts - galaxies: elliptical and lenticular, cD - galaxies: stellar content - infrared: galaxies
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