Physical properties of very powerful FRII radio galaxies

Abstract

Aims. We estimate the ages and physical properties of powerful radio galaxies.Methods. An analysis of new multi-wavelength VLA observations of eleven very powerful classical double (FRIIb) radio galaxies with redshifts between 0.4 and 1.3 is presented. We estimate ages and velocities for each side of each source. The eleven new sources are combined with previously studied samples and the characteristics of the full sample of 31 sources are studied; the full sample includes sources with redshifts between 0.056 and 1.79, and core-hot spot sizes of about 30 to 400 kpc. Results. The velocities are independent of core-hotspot separation, suggesting the rate of growth of a given source is roughly constant over the source lifetime. We combine the rate of growth, width, and pressure of a source to study the beam power, lifetime, energy, and ambient gas density using standard methods previously applied to smaller samples. Typical beam powers are in the range from 10 44 to 10 46 erg/s; we show that this quantity is insensitive to assumptions regarding minimum energy conditions. The beam powers are independent of core-hotspot separation suggesting that the beam power of a given source is roughly constant over the source lifetime. Typical total source lifetimes are found to be about a few ×(10 6 −10 7 ) years, and typical total outflow energies (E/c 2 ) are found to be about 5 × (10 5 −10 6 ) M . Ambient gas densities are found to decrease with increasing core-hotspot distance, but have no redshift dependence. Overall, the results obtained with the sample of 31 sources studied here are consistent with those obtained earlier with smaller samples.

Accretion Properties of High- And Low-Excitation Young Radio Galaxies

“…The ages of compact radio galaxies are typically estimated as t age = 10 2 -10 3 years (e.g., Orienti et al 2007;Fanti 2009;Giroletti & Polatidis 2009), while the lifetime of extended (up to a few hundred kpc) radio sources are about 10 6 -10 7 years (e.g., Alexander & Leahy 1987;Carilli et al 1991;Fanti et al 1995;O'Dea et al 2009). …”

“…Recently, a substantial amount of such compact radio galaxies have been detected and classified with various characteristics: compact symmetric objects (CSO) with a linear scale 1 kpc, gigahertz-peaked spectrum (GPS; 1 kpc) sources, mediumsize symmetric objects (1-10 kpc), and compact steep-spectrum (CSS; 20 kpc) sources (see O'Dea et al 2009). These young radio galaxies (YRGs) are a good laboratory to investigate the physical link between AGN jets and accretion disks.…”

Doppler Boosting May Have Played No Significant Role in the Finding Surveys of Radio-Loud Quasars

“…Deceleration of the flow in the kpc-scale jet has also been examined by several previous investigators [17][18][19][20][21][22] and the flow is found to slow down quickly to near 0.1c beyond a few kpc from the core. As a result radiation from most of the kpc-scale jet must then also be un-boosted.…”

“…When a jetted source contains giant lobes with internal hotspots these features will almost certainly contain most of the source flux. Since outward motion in the lobes has been shown to be close to 0.02c ± 0.01c [15][16][17] the radiation from the lobes will be un-boosted.…”

Radio interferometric observations of two core-dominated triple radio sources atz > 3

“…Liu et al 1992;O'Dea et al 2009). Even if we use this boundary, we can explain the source without any misalignment; e.g., if the approaching inner and outer jets are both inclined by φ = 20 • to the line of sight, then a bulk jet speed β inn = 0.9903 would be consistent with the measured Doppler factor in the inner region (Eq.…”