Publication: Spitzer's contribution to the AGN population
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2008-11-01
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American Astronomical Society
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Infrared selection is a potentially powerful way to identify heavily obscured AGNs missed in even the deepest X-ray surveys. Using a 24 μm-selected sample in GOODS-S, we test the reliability and completeness of three infrared AGN selection methods: (1) IRAC color-color selection, (2) IRAC power-law selection, and (3) IR-excess selection; we also evaluate a number of IR-excess approaches. We find that the vast majority of non-power-law IRAC color-selected AGN candidates in GOODS-S have colors consistent with those of star-forming galaxies. Contamination by star-forming galaxies is most prevalent at low 24 μm flux densities (~100 μJy) and high redshifts (z ~ 2), but the fraction of potential contaminants is still high (~50%) at 500 μJy, the highest flux density probed reliably by our survey. AGN candidates selected via a simple, physically motivated power-law criterion ("power-law galaxies," or PLGs), however, appear to be reliable. We confirm that the IR-excess methods successfully identify a number of AGNs, but we also find that such samples may be significantly contaminated by star-forming galaxies. Adding only the secure Spitzer-selected PLG, color-selected, IR-excess, and radio/IR-selected AGN candidates to the deepest X-ray-selected AGN samples directly increases the number of known X-ray AGNs (84) by 54%-77%, and implies an increase to the number of 24 μm-detected AGNs of 71%-94%. Finally, we show that the fraction of MIR sources dominated by an AGN decreases with decreasing MIR flux density, but only down to f_24 μ m = 300 μJy. Below this limit, the AGN fraction levels out, indicating that a nonnegligible fraction (~10%) of faint 24 μm sources (the majority of which are missed in the X-ray) are powered not by star formation, but by the central engine. The fraction of all AGNs (regardless of their MIR properties) exceeds 15% at all 24 μm flux densities.
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© 2008 The American Astronomical Society. All rights reserved.
We thank M. Polletta for providing templates, M. Dickinson, and D. Alexander for providing the list of Daddi et al. (2007a, 2007b) sources. We also thank D. Alexander, F. Fiore, M. Lacy, D. Stern, and the anonymous referee for discussions and comments that improved the paper. Finally, we thank Caltech/JPL for support through contract 1255094 to the University of Arizona. P. G. P.-G. acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA 2006Y02358 and AYA 2006Y15698YC02Y02, and from the Ramón y Cajal Program financed by the Spanish Government and the European Union.
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Alexander, D. M., Vignali, C., Bauer, F. E., Brandt, W. N., Hornschemeier, A. E., Garmire, G. P., & Schneider, D. P. 2002, AJ, 123, 1149
Alexander, D. M., et al. 2003, AJ, 126, 539
———. 2008, ApJ, in press (arXiv: 0803.0636 )
Alonso Herrero, A., et al. 2006, ApJ, 640, 167
Barmby, P., et al. 2006, ApJ, 642, 126
Bevington, P. R., & Robinson, D. K. 2003, Data Reduction and Error Analysis for the Physical Sciences (3rd ed.; Boston: McGraw-Hill)
Bolzonella, M., Miralles, J.-M., & Pelló, R. 2000, A&A, 363, 476
Bouchet, P., Lequeux, J., Maurice, E., Prevot, L., & Prevot-Burnichon, M. L. 1985, A&A, 149, 330
Brand, K., et al. 2006, ApJ, 644, 143
Brusa, M., et al. 2005, A&A, 432, 69
Buat, V., et al. 2005, ApJ, 619, L51
Calzetti, D., Armus, L., Bohlin, R. C., Kinney, A. L., Koornneef, J., & Storchi-Bergmann, T. 2000, ApJ, 533, 682
Calzetti, D., et al. 2007, ApJ, 666, 870
Caputi, K. I., et al. 2006, ApJ, 637, 727
Cardamone, C. N., et al. 2008, ApJ, 680, 130
Daddi, E., et al. 2007a, ApJ, 670, 156
———. 2007b, ApJ, 670, 173
Dale, D. A., & Helou, G. 2002, ApJ, 576, 159
Desai, V., et al. 2008, ApJ, 679, 1204
Dey, A., et al. 2008, ApJ, 677, 943
Doherty, M., Bunker, A. J., Ellis, R. S., & McCarthy, P. J. 2005, MNRAS, 361, 525
Donley, J. L., Rieke, G. H., Pérez González, P. G., Rigby, J. R., & Alonso Herrero, A. 2007, ApJ, 660, 167
Donley, J. L., Rieke, G. H., Rigby, J. R., & Pérez González, P. G. 2005, ApJ, 634, 169
Elvis, M., et al. 1994, ApJS, 95, 1
Fazio, G. G., et al. 2004, ApJS, 154, 10
Ferrarese, L., & Merritt, D. 2000, ApJ, 539, L9
Fiore, F., et al. 2008, ApJ, 672, 94
Franceschini, A., et al. 2003, MNRAS, 343, 1181
Gebhardt, K., et al. 2000, ApJ, 539, L13
Genzel, R., et al. 1998, ApJ, 498, 579
Giacconi, R., et al. 2002, ApJS, 139, 369
Giavalisco, M., et al. 2004, ApJ, 600, L93
Gilli, R., Comastri, A., & Hasinger, G. 2007, A&A, 463, 79
Goldader, J. D., Meurer, G., Heckman, T. M., Seibert, M., Sanders, D. B., Calzetti, D., & Steidel, C. C. 2002, ApJ, 568, 651
Grazian, A., et al. 2006, A&A, 449, 951
Hopkins, P. F., Hernquist, L., Cox, T. J., Di Matteo, T., Robertson, B., & Springel, V. 2006, ApJS, 163, 1
Ivezić, Ž., et al. 2002, AJ, 124, 2364
Iwasawa, K., Matt, G., Guainazzi, M., & Fabian, A. C. 2001, MNRAS, 326, 894
Kennicutt, R. C., Jr. 1998, ApJ, 498, 541
Klaas, U., et al. 2001, A&A, 379, 823
Klesman, A., & Sarajedini, V. 2007, ApJ, 665, 225
Lacy, M., Petric, A. O., Sajina, A., Canalizo, G., Storrie-Lombardi, L. J., Armus, L., Fadda, D., & Marleau, F. R. 2007, AJ, 133, 186
Lacy, M., et al. 2004, ApJS, 154, 166
———. 2005, ApJS, 161, 41
Le Fèvre, O., et al. 2004, A&A, 428, 1043
Lonsdale, C. J., et al. 2003, PASP, 115, 897
Martínez Sansigre, A., Rawlings, S., Lacy, M., Fadda, D., Jarvis, M. J., Marleau, F. R., Simpson, C., & Willott, C. J. 2006, MNRAS, 370, 1479
Marzke, R., et al. 1999, in ASP Conf. Ser. 191, Photometric Redshifts and the Detection of High Redshift Galaxies, ed. R. Waymann et al. (San Francisco: ASP), 148
McGregor, P. J. 1987, ApJ, 312, 195
Mignoli, M., et al. 2005, A&A, 437, 883
Neugebauer, G., Oke, J. B., Becklin, E. E., & Matthews, K. 1979, ApJ, 230, 79
Pérez González, P. G., et al. 2005, ApJ, 630, 82
———. 2008, ApJ, 675, 234
Persic, M., & Rephaeli, Y. 2002, A&A, 382, 843
Persic, M., Rephaeli, Y., Braito, V., Cappi, M., Della Ceca, R., Franceschini, A., & Gruber, D. E. 2004, A&A, 419, 849
Polletta, M., Weedman, D., Hönig, S., Lonsdale, C. J., Smith, H. E., & Houck, J. 2008, ApJ, 675, 960
Polletta, M., et al. 2007, ApJ, 663, 81
Pozzi, F., et al. 2007, A&A, 468, 603
Prevot, M. L., Lequeux, J., Prevot, L., Maurice, E., & Rocca-Volmerange, B. 1984, A&A, 132, 389
Ptak, A., Heckman, T., Levenson, N. A., Weaver, K., & Strickland, D. 2003, ApJ, 592, 782
Ranalli, P., Comastri, A., & Setti, G. 2003, A&A, 399, 39
Richards, E. A. 2000, ApJ, 533, 611
Richards, G. T., et al. 2003, AJ, 126, 1131
Rieke, G. H., et al. 2004, ApJS, 154, 25
Rigby, J. R., et al. 2004, ApJS, 154, 160
———. 2008, ApJ, 675, 262
Sajina, A., Lacy, M., & Scott, D. 2005, ApJ, 621, 256
Sanders, D. B., Mazzarella, J. M., Kim, D.-C., Surace, J. A., & Soifer, B. T. 2003, AJ, 126, 1607
Silva, L., Granato, G. L., Bressan, A., & Danese, L. 1998, ApJ, 509, 103
Steffen, A. T., Brandt, W. N., Alexander, D. M., Gallagher, S. C., & Lehmer, B. D. 2007, ApJ, 667, L25
Stern, D., et al. 2005, ApJ, 631, 163
Szokoly, G. P., et al. 2004, ApJS, 155, 271
Teng, S. H., Wilson, A. S., Veilleux, S., Young, A. J., Sanders, D. B., & Nagar, N. M. 2005, ApJ, 633, 664
Tozzi, P., et al. 2006, A&A, 451, 457
Treister, E., et al. 2006, ApJ, 640, 603
Vandame, B., et al. 2001, preprint (astro-ph/0102300)
Vanzella, E., et al. 2006, A&A, 454, 423
Vijh, U. P., Witt, A. N., & Gordon, K. D. 2003, ApJ, 587, 533
White, N. E., Swank, J. H., & Holt, S. S. 1983, ApJ, 270, 711
Wolf, C., et al. 2004, A&A, 421, 913
Yan, L., et al. 2007, ApJ, 658, 778