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Session 95 - Cosmological Parameters and Large Scale Structure Formation.
Oral session, Friday, January 09
International Ballroom Center,
New methods of using classical double radio sources to track evolution of structure and to estimate cosmological parameters will be discussed. It will be shown that the radio properties of a classical double radio source may be used to estimate the density and temperature of the ambient gas in the vicinity of a source. Typical values of density and temperature obtained using a sample of about 20 sources with redshifts between zero and two indicate that the sources are in cluster-like gaseous environments. This is substantiated by the fact that the composite density and temperature profiles are very similar to profiles seen in low-redshift galaxy clusters. The redshift evolution of the density and temperature can be used to track the redshift evolution of gas in the clusters, which in turn may be used to track the evolution of the dark matter in the clusters. Detailed studies of radio power selection effects and projection effects indicate these are unlikely to be important in the determination of the density and temperature, so some general conclusions about evolution of structure and the present value of the density parameter may be inferred from these results.
In addition, the sources may be used as a modified yardstick in much the same way that supernovae are used as a modified candle, to measure the global geometry of the universe. Present results favor a low-density universe, and are consistent with a flat matter-dominated universe at about the two sigma level.
