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Antonaldo Diaferio Luisa Ostorero 《Monthly notices of the Royal Astronomical Society》2009,393(1):215-223
We run adiabatic N -body/hydrodynamical simulations of isolated self-gravitating gas clouds to test whether conformal gravity, an alternative theory to general relativity, is able to explain the properties of X-ray galaxy clusters without resorting to dark matter. We show that the gas clouds rapidly reach equilibrium with a density profile which is well fitted by a β-model whose normalization and slope are in approximate agreement with observations. However, conformal gravity fails to yield the observed thermal properties of the gas cloud: (i) the mean temperature is at least an order of magnitude larger than the observed and (ii) the temperature profiles increase with the square of the distance from the cluster centre, in clear disagreement with real X-ray clusters. These results depend on a gravitational potential whose parameters reproduce the velocity rotation curves of spiral galaxies. However, this parametrization stands on an arbitrarily chosen conformal factor. It remains to be seen whether a different conformal factor, specified by a spontaneous breaking of the conformal symmetry, can reconcile this theory with observations. 相似文献
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V. A. Hagen-Thorn V. M. Larionov N. V. Efimova E. I. Hagen-Thorn A. A. Arkharov A. Di Paola M. Dolci L. O. Takalo A. Sillanpää L. Ostorero 《Astronomy Reports》2006,50(6):458-467
Multicolor (BV RIJHK) observations of the BL Lac object S5 0716+714 carried out irom 2001–2004 indicate that the spectral energy distribution
of the slowly varying component remained constant over the entire wavelength interval and over the three-year observation
period. The distribution can be represented by the power law F
v
∼ v
−1.12, providing evidence that this component has a synchrotron nature. The color characteristics of very rapid variability detected
on several nights are the same as those for the slowly varying component. An analysis of published data on the color variability
of the object for previous years indicates that the color characteristics of the slowly varying component are stable, independent
of the time intervals considered and the characteristic variability time scales. 相似文献
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