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[92.01] Ellipticals: core-Sérsic vs Nuker

D. F. Bartlett (University of Colorado)

HST has given the first look at elliptical galaxies on scales <1". Lauer et al (1995) used the Wide Field Planetary Camera (WFPC -1) to map the intensity of light I(r) in the inner 10" of 45 type E and S0 galaxies. They discovered that about 40% of the 39 ellipticals could not be described by a single power law. These galaxies have a core region where the power law I \propto r^-\gamma is less steep than the outer region I \propto r^-\beta. The resulting Nuker law allows for a smooth transition between these regions at a break radius r_b. The physical r_b varies widely: 30 pc < r_b < 1200 pc. Rest et al (2001) used WFPC -2 to confirm the original WFPC -1 results with additional galaxies.

Using the full WFPC -2 mosaic, Trujillo, Erwin, Ramos, and Graham (2004) have extended the angular range of Rest et al by a factor between 3 and 8. They find that the extended outer region is incompatible with a Nuker law. Rather the power law for the outer region must be replaced by the Sérsic law, I(r) \propto e^{-b_n r^{1/n}}. They also find that the break radius is generally much reduced. Their published study of 9 core-Sérsic galaxies has 20 pc< r_b <150 pc.

The new range of r_b fits well within 1 wavelength \lambda of the non-Newtonian sinusoidal gravity. Here the potential of a point mass is GM cos(2 \pi r/\lambda)/r and \lambda=425 pc. (Bartlett 2001, 2004). With this gravity, the potential towards the center of any spherical mass distribution varies as ±sin(2 \pi r/\lambda)/r. I identify the + sign with the core-Sérsic galaxies and the - sign with the pure Sérsic galaxies. I will relate Sérsic's n to cosmological time t.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.