The [O III] emission line luminosity function of optically selected type-2 AGN from zCOSMOS

Creators: 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.; Pellò, R.; Peng, Y.; Pérez-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.

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_☉ < L_([O III]) < 10^(9.1) L_☉. 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 [O III]λ5007 Å 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]/Hβ versus [N II]/Hα and [O III]/Hβ versus [S II]/Hα) to isolate AGN in the redshift range 0.15 < z < 0.45 and the diagnostic diagram [O III]/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 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.

Additional Information

© ESO 2010. Received 2 September 2009. Accepted 17 November 2009. A.B. wishes to thank the referee for the useful suggestions that significantly improved the manuscript. A.B. also thank H. Netzer for the the stimulating discussion, R. Fassbender for helping to improve the manuscript and S. Savaglio for sharing the expertise. This work is based on the zCOSMOS ESO Large Program Number 175.A-0839 and was supported by an INAF contract PRIN/2007/1.06.10.08, and an ASI grant ASI/COFIS/WP3110 I/026/07/0, Partial support of this work is provided by NASA ADP NNX07AT02G, CONACyT 83564, and PAPIITIN110209. These results are also based in part on observations obtained with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

Attached Files

Published - Bongiorno2010p7476Astron_Astrophys.pdf

Files

Bongiorno2010p7476Astron_Astrophys.pdf

Files (1.0 MB)

Name	Size	Download all
Bongiorno2010p7476Astron_Astrophys.pdf md5:6266367e9c01abe70726108b623dfdfe	1.0 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes