Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995aj....110..179s&link_type=abstract
Astronomical Journal v.110, p.179
Astronomy and Astrophysics
Astronomy
25
Galaxies: Individual: Ngc 3379, Galaxies: Elliptical And Lenticular
Scientific paper
We present an investigation of the radial behavior of the surface brightness fluctuations of the standard elliptical galaxy NGC 3379, and we demonstrate that it is possible to measure radial changes accurately. Our results are based on a thorough procedure, which takes into account that the unwanted point sources, such as foreground stars, background galaxies, and globular clusters, are located in a background of varying amounts of luminosity and photon fluctuations. Our reduction procedure leaves no systematic effects due to the varying detection threshold of point sources, and we arrive at a significant radial gradient in the surface brightness fluctuations {DELTA}m^bar^_I_/{DELTA} log R = - 0.29 +/- 0.08. If our broadband surface brightness profile of NGC 3379 in I is combined with a corresponding profile in B taken from the literature, the radial behavior of m^bar^_I_, may be expressed as {DELTA}m^bar^_J_,/{DELTA}(B - I) = 1.9 +/- 0.5. The weighted mean of the measured fluctuation magnitudes is m^bar^_I_ = 28.67+/-0.04. Our results have implications on the distance measurements based on surface brightness fluctuations and the discussion of the degenerate effects of age and metallicity on stellar populations of elliptical galaxies. The linear relationship between m^bar^_I_, and B - I establishes an empirical calibration, which is needed for the distance measurements based on surface brightness fluctuations. The slope of the calibration obtained for NGC 3379 seems to be in agreement with the slope achieved earlier by others for Local Group galaxies and the Fornax and Eridanus clusters. The fluctuation magnitude m^bar^_I_, proves to be a sensitive indicator for radial changes in the underlying stellar population. However, the correlation between m^bar^_I_, and B -I together with state-of-the-art synthesized models indicates that these two observables do not give independent information on the underlying stellar population.
Sodemann Marianne
Thomsen Bjarne
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