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2000ApJ...544..671W - Astrophys. J., 544, 671-685 (2000/December-1)
Empirical determinations of key physical parameters related to classical double radio sources.
WAN L., DALY R.A. and GUERRA E.J.
Abstract (from CDS):
A sample of 14 radio galaxies and eight radio-loud quasars with redshifts between 0 and 2 was studied in detail; each source has enough radio information to be able to determine each of the physical parameters listed above. The beam power was determined for each beam of each AGN (so there are two numbers for each source); these AGNs are highly symmetric in terms of beam powers. Typical beam powers are about 1045 ergs.s–1. No strong correlation is seen between the beam power and the core-hot spot separation, which suggests that the beam power is roughly constant over the lifetime of a source. The beam power increases with redshift, which is significant after excluding correlations between the radio power and redshift. The relationship between beam power and radio power is not well constrained by the current data.
The characteristic or total time the AGN will actively produce a collimated outflow is estimated. Typical total lifetimes are ~(107-108) yr. Total source lifetimes decrease with redshift. This decrease in total lifetime with increasing redshift can explain the decrease in the average source size (hot spot-hot spot separation) with redshift. Thus, high-redshift sources are smaller because they have shorter lifetimes; note that higher redshift sources grow more rapidly than low-redshift sources.
A new method of estimating the thermal pressure of the ambient gas in the vicinity of a powerful classical double radio source is presented. This new estimate is independent of synchrotron and inverse Compton aging arguments, and depends only upon the properties of the radio lobe and the shape of the radio bridge. A detailed radio map of the radio bridge at a single radio frequency can be used to estimate the thermal pressure of the ambient gas. Thermal pressures on the order of 10–10 dynes.cm–2, typical of gas in low-redshift clusters of galaxies, are found for the environments of the sources studied here. It is shown that appreciable amounts of cosmic microwave background diminution (the Sunyaev-Zeldovich effect) are expected from many of these clusters. This could be detected at high frequency where the emission from the radio sources is weak.
The total gravitational mass of the host cluster of galaxies is estimated using the composite pressure profile and the equation of hydrostatic equilibrium for cluster gas. Total masses, and mass-density profiles, similar to those of low-redshift clusters of galaxies, are obtained. Thus, some clusters of galaxies, or cores of clusters, exist at redshifts of 1-2. The redshift evolution of the cluster mass is not well determined at present. The current data do not indicate any negative evolution of the cluster mass, which may have implications for models of evolution of structure in the universe.
Abstract Copyright: ∼
Journal keyword(s): Cosmology: Observations - Galaxies: Active - Galaxies: Quasars: General - Radio Continuum: Galaxies
Simbad objects: 23
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