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 10(5.5) L-circle dot < L-[OIII] < 10(9.1) L-circle dot. 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]lambda 5007 angstrom 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 ([O III]/H beta versus [N II]/H alpha and [OIII]/H beta versus [S II]/H alpha) to isolate AGN in the redshift range 0.15 < z < 0.45 and the diagnostic diagram [O III]/H beta versus [O II]/H beta 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 luminosity-dependent 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$^{ m,}$ / Bongiorno, A.; Mignoli, M.; Zamorani, G.; Lamareille, F.; Lanzuisi, G.; Miyaji, T.; Bolzonella, M.; Carollo, C. M.; Contini, T.; Kneib, J. P.; Le Fèvre, O.; Lilly, S. J.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Brusa, M.; Caputi, K.; Civano, F.; Coppa, G.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Halliday, C.; Hasinger, G.; Koekemoer, A. M.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J. -F.; Le Brun, V.; Maier, C.; Merloni, A.; Nair, P.; Pello, R.; Peng, Y.; Perez Montero, E.; Ricciardelli, E.; Salvato, M.; Silverman, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Abbas, U.; Bottini, D.; Cappi, A.; Cassata, P.; Cimatti, A.; Guzzo, L.; Leauthaud, A.; Maccagni, D.; Marinoni, C.; Mccracken, H. J.; Memeo, P.; Meneux, B.; Oesch, P.; Porciani, C.; Pozzetti, L.; Scaramella, R.. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - 510:(2010), p. A56. [10.1051/0004-6361/200913229]
The [O iii] emission line luminosity function of optically selected type-2 AGN from zCOSMOS$^{ m,}$
Coppa, G.;
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 10(5.5) L-circle dot < L-[OIII] < 10(9.1) L-circle dot. 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]lambda 5007 angstrom 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 ([O III]/H beta versus [N II]/H alpha and [OIII]/H beta versus [S II]/H alpha) to isolate AGN in the redshift range 0.15 < z < 0.45 and the diagnostic diagram [O III]/H beta versus [O II]/H beta 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 luminosity-dependent 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.| File | Dimensione | Formato | |
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