The radio luminosity function from the low-frequency 3CRR, 6CE and 7CRS complete samples

By C. Willott, S. Rawlings, K. Blundell, M. Lacy, S. Eales. 2000

247 citations recorded by the source corpus.

We measure the radio luminosity function (RLF) of steep-spectrum radio sources using three redshift surveys of flux-limited samples selected at low (151 and 178 MHz) radio frequency, low-frequency source counts and the local RLF. The redshift surveys used are the new 7C Redshift Survey (7CRS) and the brighter 3CRR and 6CE surveys totalling 356 sources with virtually complete redshift z information. This yields unprecedented coverage of the radio luminosity versus z plane for steep-spectrum sources, and hence the most accurate measurements of the steep-spectrum RLF yet made. We find that a simple dual-population model for the RLF fits the data well, requiring differential density evolution (with z) for the two populations. The low-luminosity population can be associated with radio galaxies with weak emission lines, and includes sources with both FRI and FRII radio structures; its comoving space density ρ rises by about one dex between z∼0 and 1 but cannot yet be meaningfully constrained at higher redshifts. The high-luminosity population can be associated with radio galaxies and quasars with strong emission lines, and consists almost exclusively of sources with FRII radio structure; its ρ rises by nearly three dex between z∼0 and 2. These results mirror the situation seen in X-ray and optically selected samples of AGN where: (i) low-luminosity objects exhibit a gradual rise in ρ with z that crudely matches the rises seen in the rates of global star formation and galaxy mergers; and (ii) the density of high-luminosity objects rises much more dramatically. The integrated radio luminosity density of the combination of the two populations is controlled by the value of ρ at the low-luminosity end of the RLF of the high-luminosity population, a quantity which has been directly measured at z∼1 by the 7CRS. We argue that robust determination of this quantity at higher redshifts requires a new redshift survey based on a large (∼1000 source) sample about five times fainter than the 7CRS.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/f3d01c3de0c44ead7f3655762d44404c467348ef

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Citations in the corpus

THE EVOLUTION OF SWIFT/BAT BLAZARS AND THE ORIGIN OF THE MeV BACKGROUND (2009, background): “Indeed, the two blazar sub-populations, BL Lacertae (BL Lac) objects and flat spectrum radio quasars (FSRQs), are thought to be the beamed counterparts of low- and high-luminosity radio galaxies, respectively (Wall & Jackson 1997; Willott et al. 2001).”
Radio and millimeter continuum surveys and their astrophysical implications (2009, result): “The latter findings are consistent with those by Willott et al. (2001), who used emission-line strength rather than morphology (FR I/FR II) to discriminate between radio-source populations.”
Science with ASKAP (2008, background): “The space density of radio active objects is handed over at z < 1 from the highluminosity FRII radio galaxies of the ‘evolution bulge’ to the mildy evolving and lower-luminosity radio galaxies which dominate the space density at local epochs [87, 175, 279].”
A semi-empirical simulation of the extragalactic radio continuum sky for next generation radio telescopes (2008, methodology): “For the classical double-lobed radio-loud AGN, we use the 151 MHz luminosity function derived by Willott et al. (2001) from a compilation of low-frequency-selected samples.”
Distant radio galaxies and their environments (2008, background): “The number density of radio sources with this luminosity in the redshift range 2 < z < 5 is a few times 10−8 Mpc−3, with large uncertainties (Dunlop and Peacock 1990; Willott et al 2001; Venemans et al 2007).”
Protoclusters associated with z > 2 radio galaxies - I. Characteristics of high redshift protoclusters (2006, background): “Using the more recent radio luminosity function at 151 MHz as derived by Willott et al. (2001) and assuming a spectral slope ofα ≃ −1.0 gives a number density that is similar within a factor of 2.”
Evidence for powerful AGN winds at high redshift: dynamics of galactic outflows in radio galaxies during the “Quasar Era” (2008, background): “Willott et al. (2001) studied the redshift evolution of the radio luminosity function and find a population of galaxies with radio powers P151MHz ∼ 10 26.5−29.5 W Hz−1 at 151 MHz, which shows a strong peak near z∼ 2 and rapidly declines towards lower redshifts.”
THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS (2013, background): “…slowing down of the evolution with decreasing source luminosity has been observed in many kinds of AGN, including the population of radio galaxies (Longair 1966; Schmidt 1972; Willott et al. 2001), but an inversion of the evolution at very low luminosity as observed here is difficult to interpret.”
On the evolution of the black‐hole/spheroid mass ratio (2005, background): “Indeed, the 3CRR quasar sample is known to be consistent with being randomly distributed with respect to our line of sight, with orientation angles restricted to≤ 53◦ (Willott et al. 2001).”
CONTRIBUTION OF GAMMA-RAY-LOUD RADIO GALAXIES’ CORE EMISSIONS TO THE COSMIC MeV AND GeV GAMMA-RAY BACKGROUND RADIATION (2011, methodology): “The RLF is given by ρr (Lr, z) = η(z) × [ρr,FRI(Lr, z) + ρr,FRII(Lr, z)], (7) where η(z) is the conversion factor of cosmology, ρr,FRI is the FRI RLF, and ρr,FRII is the FRII RLF.”
SIMULATIONS OF THE MICROWAVE SKY (2009, background): “These two populations can be roughly identified with the type II and I classification of radio sources by Fanaroff & Riley (1974), respectively (however, see discussions in Willott et al. 2001).”
The anti‐hierarchical growth of supermassive black holes (2004, methodology): “…physical arguments invoking the same inner engine for radio and X-ray selected AGN, there are indeed strong similarities between the cosmic evolution of radio sources and of X-ray and optically selected AGN (Dunlop 1998; Willott et al. 2001), a further hint of the correctness of this assumption.”
The star formation history of K-selected galaxies (2008, background): “The evolution of these two types of radio-emitting AGN differs, with FR ii sources undergoing strong evolution (Dunlop & Peacock 1990; Willott et al. 2001) while FR i sources undergo a weaker evolution or possibly maintain a constant co-moving space density (Clewley & Jarvis 2004; Sadler et al.…”