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Ongoing and Co-Evolving Star Formation in zCOSMOS Galaxies Hosting Active Galactic Nuclei

Silverman, J. D. and Lamareille, F. and Maier, C. and Lilly, S. J. and Mainieri, V. and Brusa, M. and Cappelluti, N. and Hasinger, G. and Zamorani, G. and Scodeggio, M. and Bolzonella, M. and Contini, T. and Carollo, C. M. and Jahnke, K. and Kneib, J.-P. and Le Fèvre, O. and Merloni, A. and Bardelli, S. and Bongiorno, A. and Brunner, H. and Caputi, K. and Civano, F. and Comastri, A. and Coppa, G. and Cucciati, O. and de la Torre, S. and de Ravel, L. and Elvis, M. and Finoguenov, A. and Fiore, F. and Franzetti, P. and Garilli, B. and Gilli, R. and Iovino, A. and Kampczyk, P. and Knobel, C. and Kovač, K. and Le Borgne, J.-F. and Le Brun, V. and Mignoli, M. and Pello, R. and Peng, Y. and Perez Montero, E. and Ricciardelli, E. and Tanaka, M. and Tasca, L. and Tresse, L. and Vergani, D. and Vignali, C. and Zucca, E. and Bottini, D. and Cappi, A. and Cassata, P. and Fumana, M. and Griffiths, R. and Kartaltepe, J. and Koekemoer, A. and Marinoni, C. and McCracken, H. J. and Memeo, P. and Meneux, B. and Oesch, P. and Porciani, C. and Salvato, M. (2009) Ongoing and Co-Evolving Star Formation in zCOSMOS Galaxies Hosting Active Galactic Nuclei. Astrophysical Journal, 696 (1). pp. 396-410. ISSN 0004-637X.

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We present a study of the host galaxies of active galactic nucleus (AGN) selected from the zCOSMOS survey to establish if accretion onto supermassive black holes (SMBHs) and star formation are explicitly linked up to z ~ 1. We identify 152 galaxies that harbor AGN, based on their X-ray emission (L_(0.5-10 keV) > 10^(42) erg s^(–1)) detected by XMM-Newton observations of 7543 galaxies (i_(acs) < 22.5). Star formation rates (SFRs), including those weighted by stellar mass, of a subsample are determined using the [O II]λ3727 emission-line luminosity, corrected for an AGN contribution based on the observed [O III]λ5007 strength or that inferred by their hard (2-10 keV) X-ray luminosity. We find that an overwhelming majority of AGN host galaxies have significant levels of star formation with a distribution spanning ~1-100 M⊙ yr^(–1); their average SFR is higher than that of galaxies with equivalent stellar mass (M_* > 4 × 10^(10) M⊙). The close association between AGN activity and star formation is further substantiated by an increase in the fraction of galaxies hosting AGN with the youthfulness of their stars as indicated by the rest-frame color (U–V) and spectral index D_n(4000); we demonstrate that a mass-selected sample is required to alleviate an artificial peak in the AGN fraction falling in the transition region due to the fact that many "blue cloud" galaxies have low mass-to-light ratios in luminosity-limited samples. We also find that the SFRs of AGN hosts evolve with cosmic time in a manner that closely mirrors the overall galaxy population and naturally explains the low SFRs in AGNs (z < 0.3) from the SDSS. We conclude that the conditions most conducive for AGN activity are a massive host galaxy and a large reservoir of gas. Furthermore, a direct correlation between mass-accretion rate onto SMBHs and SFR is shown to be weak although the average ratio (~10–2) is constant with redshift, effectively shifting the evidence for a co-evolution scenario in a statistical manner to smaller physical scales (i.e., within the same galaxies). The order-of-magnitude increase in this ratio compared to the locally measured value of M_(BH)/M_(bulge) is consistent with an AGN lifetime substantially shorter than that of star formation. Our findings illustrate an intermittent scenario with underlying complexities regarding fueling over vastly different physical (and temporal) scales yet to be firmly determined.

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Additional Information:© 2009 The American Astronomical Society. Received 2008 July 15; accepted 2009 January 13; published 2009 April 15. We are most grateful to the referee for providing a critical review that significantly improved the paper and to Minjin Kim for allowing us to use his emission-line measurements of SDSS AGNs and fielding subsequent communications. This work is fully based on observations undertaken at the European Southern Observatory (ESO) Very Large Telescope (VLT) under the Large Program 175.A-0839 (PI: S. Lilly). Facilities: XMM, VLT:Melipal (VIMOS).
Subject Keywords:galaxies: active; galaxies: evolution; quasars: emission lines; quasars: general; X-rays: galaxies
Record Number:CaltechAUTHORS:20090831-140313251
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Official Citation:Ongoing and Co-Evolving Star Formation in zCOSMOS Galaxies Hosting Active Galactic Nuclei J. D. Silverman, F. Lamareille, C. Maier, S. J. Lilly, V. Mainieri, M. Brusa, N. Cappelluti, G. Hasinger, G. Zamorani, M. Scodeggio, M. Bolzonella, T. Contini, C. M. Carollo, K. Jahnke, J.-P. Kneib, O. Le Fèvre, A. Merloni, S. Bardelli, A. Bongiorno, H. Brunner, K. Caputi, F. Civano, A. Comastri, G. Coppa, O. Cucciati, S. de la Torre, L. de Ravel, M. Elvis, A. Finoguenov, F. Fiore, P. Franzetti, B. Garilli, R. Gilli, A. Iovino, P. Kampczyk, C. Knobel, K. Kovač, J.-F. Le Borgne, V. Le Brun, M. Mignoli, R. Pello, Y. Peng, E. Perez Montero, E. Ricciardelli, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, C. Vignali, E. Zucca, D. Bottini, A. Cappi, P. Cassata, M. Fumana, R. Griffiths, J. Kartaltepe, A. Koekemoer, C. Marinoni, H. J. McCracken, P. Memeo, B. Meneux, P. Oesch, C. Porciani, and M. Salvato 2009 ApJ 696 396-410 doi: 10.1088/0004-637X/696/1/396.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15493
Deposited By: Tony Diaz
Deposited On:14 Sep 2009 19:09
Last Modified:07 Jul 2015 20:13

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