Open AccessOn the radio properties of the highest redshift quasars
Author(s) -
Cirasuolo M.,
Magliocchetti M.,
Gentile G.,
Celotti A.,
Cristiani S.,
Danese L.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10695.x
Subject(s) - quasar , physics , astrophysics , redshift , sky , ovv quasar , astronomy , luminosity , cosmology , population , luminosity function , active galactic nucleus , universe , galaxy , demography , sociology
We present deep radio observations of the most distant complete quasar sample drawn from the Sloan Digital Sky Survey. Combining our new data with those from literature, we obtain a sample which is ∼100 per cent complete down to S 1.4 GHz = 60 μJy over the redshift range 3.8 ≤ z ≤ 5 . The fraction of radio detections is relatively high (∼43 per cent), similar to what observed locally in bright optical surveys. Even though the combined radio and optical properties of quasars remain overall unchanged from z ∼ 5 to the local Universe, there is some evidence for a slight overabundance of radio‐loud (RL) sources at the highest redshifts when compared with the lower‐ z regime. Exploiting the deep radio Very Large Array observations, we present the first attempt to directly derive the radio luminosity function of bright quasars at z ≳ 4 . The unique depth – both in radio and optical – allows us to thoroughly explore the population of optically bright Fanaroff–Riley type II (FR II) quasars up to z ∼ 5 and opens a window on the behaviour of the brightest FR I sources. A close investigation of the space density of RL quasars also suggests a differential evolution, with the more luminous sources showing a less‐pronounced cut‐off at high z when compared with the less‐luminous ones.