A Study of 3CR Radio Galaxies from [ITAL][CLC]z[/CLC][/ITAL] = 0.15 to [ITAL][CLC]z[/CLC][/ITAL] = 0.65. II. Evidence for an Evolving Radio Structure

Abstract

Radio morphology data have been collected for a sample of radio galaxies from the Revised Third Cambridge Catalog in the redshift range 0.15 < z < 0.65. Radio structure parameters including largest physical size, projected bending angle ( ), lobe length asymmetry (Q), and hot spot placement (Fanaroff-Riley ratio) have been measured from the highest-quality radio maps available. Combined with similar data for quasars in the same redshift range, these morphology data are used in conjunction with a quantification of the richness of the cluster environment around these objects (the amplitude of the galaxy-galaxy spatial covariance function, B gg ) to search for indirect evidence of a dense intracluster medium (ICM). This is accomplished by searching for confinement and distortions of the radio structure that are correlated with B gg . Correlations between physical size and hot spot placement with B gg show evidence for an ICM only at z 0.4, but there are no correlations at z ! 0.4, suggesting an epoch of z $ 0.4 for the formation of the ICM in these Abell richness class 0-1, FR2-selected clusters. X-ray-selected clusters at comparable redshifts, which contain FR1 type sources exclusively, are demonstrably richer than the FR2-selected clusters found in this study. The majority of the radio sources with high B gg values at z 0.4 can be described as '' fat doubles '' or intermediate FR2-FR1s. The lack of correlation between B gg and or B gg and Q suggests that these types of radio source distortion are caused by something other than interaction with a dense ICM. Therefore, a large cannot be used as an unambiguous indicator of a rich cluster around powerful radio sources. These results support the hypothesis made in our earlier paper that cluster quasars fade to become FR2s, then FR1s, on a timescale of 0.9 Gyr (for H 0 = 50 km s À1 Mpc À1 ).

Nature and evolution of powerful radio galaxies at z ∼ 1 and their link with the quasar luminosity function

“…This implies that size evolution at z > 1 only affects sources smaller than d = 150 kpc and thus support the idea that FR II size evolution is determined by the interaction of the jet with gas close to the host galaxy, as suggested by Neeser et al (1995). The lack of a correlation between cluster richness and physical size for 3CR sources at z > 0.4 (Harvanek & Stocke 2002) is further evidence that size evolution is due to changes on scales below 10 2 kpc. Strong evidence for evolution of the radio-loud fraction with redshift and luminosity has been observed by Jiang et al (2007).…”

ACHANDRAOBSERVATION OF 3C 288—REHEATING THE COOL CORE OF A 3 keV CLUSTER FROM A NUCLEAR OUTBURST atz= 0.246

“…However, "high-excitation" FR II sources tend to lie in low gas mass atmospheres at least at low redshifts (Ellingson et al 1991a(Ellingson et al , 1991b(Ellingson et al , 1991cHarvanek et al 2001Harvanek et al , 2002Isobe et al 2005;Kraft et al 2007), unless the mechanical power of the jet is unusually high (e.g., Cygnus A; Smith et al 2002). This strongly suggests that the jet power and the interaction between jets and the hot gas in their vicinity play pivotal roles in governing the overall morphology (FR I versus FR II) of the radio source.…”

The interaction of 3C 401 with the surrounding intracluster medium

“…In this paper, we describe an observation of the moderately powerful ( P 20 cm = 5 × 10 26 W Hz −1 ) radio galaxy 3C 401 ( z = 0.201) by Chandra . Despite having Fanaroff–Riley type II (FRII) radio power, this source has been classified as intermediate between an FRI and FRII morphologically (Harvanek & Stocke 2002), raising the possibility that it might be an example of a fading radio source. Specifically, 3C 401 contains no highly concentrated ‘hotspots’ at the leading edges of its two lobes, and the brightest portion of its extended structure is a luminous jet in the southern lobe.…”

“…3C 401 is also much broader compared to its length than a typical FRII – thus, the nickname given to sources with this morphology: ‘fat doubles’. See Harvanek & Stocke (2002) for an identification and discussion of other ‘fat doubles’, including Hercules A. 3C 401 is surrounded by a cluster of galaxies with optical galaxy density (with the galaxy–galaxy two‐point correlation function B gg ≈ 1100 Mpc 1.77 ; Harvanek et al 2001), equivalent to Abell richness class I–II.…”