Veilleux, S. and Rupke, D. S. N. and Kim, D.-C. and Genzel, R. and Sturm, E. and Lutz, D. and Contursi, A. and Schweitzer, M. and Tacconi, L. J. and Netzer, H. and Sternberg, A. and Mihos, J. C. and Baker, A. J. and Mazzarella, J. M. and Lord, S. and Sanders, D. B. and Stockton, A. and Joseph, R. D. and Barnes, J. E. (2009) Spitzer Quasar and Ulirg Evolution Study (QUEST). IV. Comparison of 1 Jy Ultraluminous Infrared Galaxies with Palomar-Green Quasars. Astrophysical Journal Supplement Series, 182 (2). pp. 628-666. ISSN 0067-0049 http://resolver.caltech.edu/CaltechAUTHORS:20090901-084544830
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We report the results from a comprehensive study of 74 ultraluminous infrared galaxies (ULIRGs) and 34 Palomar-Green (PG) quasars within z ~ 0.3 observed with the Spitzer Infrared Spectrograph (IRS). The contribution of nuclear activity to the bolometric luminosity in these systems is quantified using six independent methods that span a range in wavelength and give consistent results within ~±10%-15% on average. This agreement suggests that deeply buried active galactic nuclei (AGNs) invisible to Spitzer IRS but bright in the far-infrared are not common in this sample. The average derived AGN contribution in ULIRGs is ~35%-40%, ranging from ~15%-35% among "cool" (f_(25)/f_(60) ≤ 0.2) optically classified H II-like and LINER ULIRGs to ~50 and ~75% among warm Seyfert 2 and Seyfert 1 ULIRGs, respectively. This number exceeds ~80% in PG QSOs. ULIRGs fall in one of three distinct AGN classes: (1) objects with small extinctions and large polycyclic aromatic hydrocarbon (PAH) equivalent widths are highly starburst-dominated; (2) systems with large extinctions and modest PAH equivalent widths have larger AGN contributions, but still tend to be starburst-dominated; and (3) ULIRGs with both small extinctions and small PAH equivalent widths host AGN that are at least as powerful as the starbursts. The AGN contributions in class 2 ULIRGs are more uncertain than in the other objects, and we cannot formally rule out the possibility that these objects represent a physically distinct type of ULIRGs. A morphological trend is seen along the sequence (1)-(2)-(3), in general agreement with the standard ULIRG–QSO evolution scenario and suggestive of a broad peak in extinction during the intermediate stages of merger evolution. However, the scatter in this sequence, including the presence of a significant number of AGN-dominated systems prior to coalescence and starburst-dominated but fully merged systems, implies that black hole accretion, in addition to depending on the merger phase, also has a strong chaotic/random component, as in local AGNs.
|Additional Information:||© 2009 The American Astronomical Society. Received 2008 December 18; accepted 2009 April 9; published 2009 May 21. This work is based on observations carried out with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contact 1407. Support for this work was provided by NASA through contracts 1263752 (S.V., D.S.N.R., and D.C.K.), 101185-07.E.7991.01.08 (J.M., S.L.), 1264025 (J.C.M.), and 1264791 (D.B.S. A.S., R.D.J., J.E.B.) issued by JPL/Caltech. S. V. acknowledges support from a Senior Award from the Alexander von Humboldt Foundation and thanks the host institution, MPE Garching, where some of this work was performed. We thank the anonymous referee for a critical reading of the manuscript and acknowledge useful conversations with G. Share and J. Gracia Carpio. This work has made use of NASA’s Astrophysics Data System Abstract Service and the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The SMART software package was developed by the IRS team at Cornell University and is available through the Spitzer Science Center at Caltech.|
|Subject Keywords:||galaxies: active; galaxies: interactions; galaxies: Seyfert; galaxies: starburst; infrared: galaxies; quasars: general|
|Official Citation:||Spitzer Quasar and Ulirg Evolution Study (QUEST). IV. Comparison of 1 Jy Ultraluminous Infrared Galaxies with Palomar-Green Quasars S. Veilleux, D. S. N. Rupke, D.-C. Kim, R. Genzel, E. Sturm, D. Lutz, A. Contursi, M. Schweitzer, L. J. Tacconi, H. Netzer, A. Sternberg, J. C. Mihos, A. J. Baker, J. M. Mazzarella, S. Lord, D. B. Sanders, A. Stockton, R. D. Joseph, and J. E. Barnes 2009 ApJS 182 628-666 doi: 10.1088/0067-0049/182/2/628.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||04 Sep 2009 18:45|
|Last Modified:||26 Dec 2012 11:17|
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