The quasar sample selected by cross-correlating the FIRST and the 2dF Quasar Redshift Surveys allows us to explore, for the first time, the faint end of the radio and optical luminosity functions up to z = 2.2. We find indications (~3 \sigma) of a negative evolution for these faint sources at z > 1.8, both in radio and optical bands. This corresponds to a decrement in the space density of faint quasars of about a factor 2 at z=2.2 and confirms the presence of a differential evolution for the population of radio-active quasars. The faint end of both luminosity functions flattens and the comparison with the (optical) number density of the whole quasar population supports a dependence of the fraction of radio detected quasars on the optical luminosity. A progressive decrease in the fraction of quasars in the whole radio source population can be consistently accounted for within the `receding torus' scenario. The population of low luminosity quasars, which the FIRST-2dF detects, appears to depart from the `classical' scheme for radio-loud quasars.

Faint radio-loud quasars: clues on their evolution / Cirasuolo, M.; Magliocchetti, M.; Celotti, Anna Lisa. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 357:4(2005), pp. 1267-1280. [10.1111/j.1365-2966.2005.08729.x]

Faint radio-loud quasars: clues on their evolution

Celotti, Anna Lisa
2005-01-01

Abstract

The quasar sample selected by cross-correlating the FIRST and the 2dF Quasar Redshift Surveys allows us to explore, for the first time, the faint end of the radio and optical luminosity functions up to z = 2.2. We find indications (~3 \sigma) of a negative evolution for these faint sources at z > 1.8, both in radio and optical bands. This corresponds to a decrement in the space density of faint quasars of about a factor 2 at z=2.2 and confirms the presence of a differential evolution for the population of radio-active quasars. The faint end of both luminosity functions flattens and the comparison with the (optical) number density of the whole quasar population supports a dependence of the fraction of radio detected quasars on the optical luminosity. A progressive decrease in the fraction of quasars in the whole radio source population can be consistently accounted for within the `receding torus' scenario. The population of low luminosity quasars, which the FIRST-2dF detects, appears to depart from the `classical' scheme for radio-loud quasars.
2005
357
4
1267
1280
https://doi.org/10.1111/j.1365-2966.2005.08729.x
https://arxiv.org/abs/astro-ph/0412131
Cirasuolo, M.; Magliocchetti, M.; Celotti, Anna Lisa
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/13967
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