Aims: We present a catalog of 213 type-2 AGN selected from the zCOSMOS survey. The selected sample covers a wide redshift range (0.15 < z < 0.92) and is deeper than any other previous study, encompassing the luminosity range 105.5Lâ< L[OIII]< 109.1Lâ. We explore the intrinsic properties of these AGN and the relation to their X-ray emission (derived from the XMM-COSMOS observations). We study their evolution by computing the [OIII]λ5007 à line luminosity function (LF) and we constrain the fraction of obscured AGN as a function of luminosity and redshift. Methods: The sample was selected on the basis of the optical emission line ratios, after applying a cut to the signal-to-noise ratio (S/N) of the relevant lines.We used the standard diagnostic diagrams ([OIII]/Hβ versus [N ii]/Hα and [OIII]/Hβ versus [S ii]/Hα) to isolate AGN in the redshift range 0.15 < z < 0.45 and the diagnostic diagram [OIII]/Hβ versus [O II]/Hβ to extend the selection to higher redshift (0.5 < z < 0.92). Results: Combining our sample with one drawn from SDSS, we found that the best description of the evolution of type-2 AGN is a luminositydependent density evolution model. Moreover, using the type-1 AGN LF we were able to constrain the fraction of type-2 AGN to the total (type-1 + type-2) AGN population. We found that the type-2 fraction decreases with luminosity, in agreement with the most recent results, and shows signs of a slight increase with redshift. However, the trend with luminosity is visible only after combining the SDSS+zCOSMOS samples. From the COSMOS data points alone, the type-2 fraction seems to be quite constant with luminosity.
The [O III] emission line luminosity function of optically selected type-2 AGN from zCOSMOS / A. Bongiorno, M. Mignoli, G. Zamorani, F. Lamareille, G. Lanzuisi, T. Miyaji, M. Bolzonella, C.M. Carollo, T. Contini, J.P. Kneib, O. Le Fèvre, S.J. Lilly, V. Mainieri, A. Renzini, M. Scodeggio, S. Bardelli, M. Brusa, K. Caputi, F. Civano, G. Coppa, O. Cucciati, S. De La Torre, L. De Ravel, P. Franzetti, B. Garilli, C. Halliday, G. Hasinger, A.M. Koekemoer, A. Iovino, P. Kampczyk, C. Knobel, K. Kovač, J.-. Le Borgne, V. Le Brun, C. Maier, A. Merloni, P. Nair, R. Pello, Y. Peng, E. Perez Montero, E. Ricciardelli, M. Salvato, J. Silverman, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, E. Zucca, U. Abbas, D. Bottini, A. Cappi, P. Cassata, A. Cimatti, L. Guzzo, A. Leauthaud, D. Maccagni, C. Marinoni, H.J. Mccracken, P. Memeo, B. Meneux, P. Oesch, C. Porciani, L. Pozzetti, N. Scaramella R.. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 510:1(2010), pp. A56.1-A56.15.
The [O III] emission line luminosity function of optically selected type-2 AGN from zCOSMOS
L. Guzzo;
2010
Abstract
Aims: We present a catalog of 213 type-2 AGN selected from the zCOSMOS survey. The selected sample covers a wide redshift range (0.15 < z < 0.92) and is deeper than any other previous study, encompassing the luminosity range 105.5Lâ< L[OIII]< 109.1Lâ. We explore the intrinsic properties of these AGN and the relation to their X-ray emission (derived from the XMM-COSMOS observations). We study their evolution by computing the [OIII]λ5007 à line luminosity function (LF) and we constrain the fraction of obscured AGN as a function of luminosity and redshift. Methods: The sample was selected on the basis of the optical emission line ratios, after applying a cut to the signal-to-noise ratio (S/N) of the relevant lines.We used the standard diagnostic diagrams ([OIII]/Hβ versus [N ii]/Hα and [OIII]/Hβ versus [S ii]/Hα) to isolate AGN in the redshift range 0.15 < z < 0.45 and the diagnostic diagram [OIII]/Hβ versus [O II]/Hβ to extend the selection to higher redshift (0.5 < z < 0.92). Results: Combining our sample with one drawn from SDSS, we found that the best description of the evolution of type-2 AGN is a luminositydependent density evolution model. Moreover, using the type-1 AGN LF we were able to constrain the fraction of type-2 AGN to the total (type-1 + type-2) AGN population. We found that the type-2 fraction decreases with luminosity, in agreement with the most recent results, and shows signs of a slight increase with redshift. However, the trend with luminosity is visible only after combining the SDSS+zCOSMOS samples. From the COSMOS data points alone, the type-2 fraction seems to be quite constant with luminosity.
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