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Published May 1, 2009 | Erratum + Published
Journal Article Open

Cosmic Evolution of Radio Selected Active Galactic Nuclei in the Cosmos Field


We explore the cosmic evolution of radio luminous active galactic nuclei (AGNs) with low radio powers (L_(1.4 GHz) ≾ 5 × 10^(25) W Hz^(–1)) out to z = 1.3 using to date the largest sample of ~600 low-luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio-luminosity function for these AGNs, and its evolution with cosmic time assuming two extreme cases: (1) pure luminosity and (2) pure density evolution. The former and latter yield L_* α (1 + z)^(0.8 ± 0.1), and Φ_* α (1 + z)^(1.1 ± 0.1), respectively, both implying a fairly modest change in properties of low-radio-power AGNs since z = 1.3. We show that this is in stark contrast with the evolution of powerful (L_(1.4 GHz) > 5 × 10^25 W Hz^(–1)) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willot et al. We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGNs. Our findings suggest that high- and low-radio-power AGN activities are triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z ~ 1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the "radio mode" in cosmological models.

Additional Information

© 2009 The American Astronomical Society. Received 2008 September 25; accepted 2009 January 21; published 2009 April 13. The authors are grateful to P. N. Best for especially deriving the SDSS/NVSS radio source fractions as a function of stellar mass with a radio luminosity cut that matches the VLA– COSMOS survey data. C.C. acknowledges support from the Max-Planck Society and the Alexander von Humboldt Foundation through the Max-Planck-Forschungspreis 2005. G.Z. and S.B. acknowledge support from an INAF contract PRIN- 2006/ and an ASI grant ASI/COFIS I/026/07/0. TP acknowledges support from PSC-CUNY grant no. 69612-00 38.


ERRATUM: "Cosmic Evolution of Radio Selected Active Galactic Nuclei in the COSMOS Field" (2009, ApJ, 696, 24) V. Smolčić, G. Zamorani, E. Schinnerer, S. Bardelli, M. Bondi, L. Bîrzan, C. L. Carilli, P. Ciliegi, M. Elvis, C. D. Impey, A. M. Koekemoer, A. Merloni, T. Paglione, M. Salvato, M. Scodeggio, N. Scoville, and J. R. Trump. doi: 10.1088/0004-637X/708/1/909 The scale of the volume-averaged heating rate for the VLA-COSMOS AGN, presented in Figure 14 of the paper, requires a systematic (positive) correction due to a bug in the code used to produce this plot. The modified figure is shown below. We would like to note that the applied correction does not alter any results presented in the paper, but only strengthens the agreement between the observations and the Croton et al. (2006) cosmological model in terms of the relevance of radio mode AGN feedback in the process of massive galaxy formation. Published 2009 December 15

Attached Files

Published - Smolcic2009p2253Astrophys_J.pdf

Erratum - Smolcic2010p6760Astrophys_J.pdf


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