Unveiling Obscured Accretion in the Chandra Deep Field-South

By F. Fiore, A. Grazian, P. Santini, S. Puccetti, M. Brusa, C. Feruglio, A. Fontana, E. Giallongo, A. Comastri, C. Gruppioni and 3 more. 2007

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We make use of deep HST, VLT, Spitzer, and Chandra data on the Chandra Deep Field-South to constrain the number of Compton-thick AGNs in this field. We show that sources with high 24 μm-to-optical flux ratios and red colors form a distinct source population, and that their infrared luminosity is dominated by AGN emission. Analysis of the X-ray properties of these extreme sources shows that most of them (80% ± 15%) are indeed likely to be highly obscured, Compton-thick AGNs. The number of infrared-selected, Compton-thick AGNs with 5.8 μm luminosity higher than 1044.2 ergs s−1 turns out to be similar to that of X-ray-selected, unobscured, and moderately obscured AGNs with 2-10 keV luminosity higher than 1043 ergs s−1 in the redshift bin 1.2-2.6. This “factor of 2” source population is exactly what is needed to solve the discrepancies between model predictions and X-ray AGN selection.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/ffece7fde913ba0e97b46f5d02a967f9fedf4296

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MID-INFRARED SELECTION OF ACTIVE GALACTIC NUCLEI WITH THE WIDE-FIELD INFRARED SURVEY EXPLORER. I. CHARACTERIZING WISE-SELECTED ACTIVE GALACTIC NUCLEI IN COSMOS (2012, background): “…from deep Chandra and Spitzer imaging of targeted surveys, significant advances have come in recent years at understanding the full census of AGN (e.g., Polletta et al. 2006; Hickox et al. 2007; Fiore et al. 2008; Gorjian et al. 2008; Comastri et al. 2011; Hickox et al. 2011; Mullaney et al. 2011).”
The evolution of the dust and gas content in galaxies (2013, background): “…we remove all known AGNs from the catalogues (∼2.5% of the total final sample), by considering X-ray detected sources (the AGN sample of Santini et al. 2012b), highly obscured AGNs detected through their mid-IR (MIR) excess (following Fiore et al. 2008), and IRAC selected AGNs (Donley et al. 2012).”
Multiwavelength Study of Massive Galaxies at z ~ 2. II. Widespread Compton-thick Active Galactic Nuclei and the Concurrent Growth of Black Holes and Bulges (2007, background): “In parallel to this work, Fiore et al. (2007) detected a similar population ofz∼ 2 obscured AGNs from X-ray stacking of galaxies with large 24µm to optical flux ratios.”
THE RISE AND FALL OF PASSIVE DISK GALAXIES: MORPHOLOGICAL EVOLUTION ALONG THE RED SEQUENCE REVEALED BY COSMOS (2009, background): “We note that a significant fraction of 24µm emission, especially among the passive population, might arise from AGN (e.g., Fiore et al. 2008).”
IDENTIFYING LUMINOUS ACTIVE GALACTIC NUCLEI IN DEEP SURVEYS: REVISED IRAC SELECTION CRITERIA (2012, background): “While many MIR-based selection criteria are therefore designed to specifically target heavily obscured AGN (e.g., Daddi et al. 2007b; Fiore et al. 2008, 2009), Spitzer IRAC selection is sensitive to the hot dust signature present in ∼> 80 − 95% of luminous AGN regardless of obscuration (Hao et al.…”
Star formation and mass assembly in high-redshift galaxies (2009, methodology): “Following a different approach, Fiore et al. (2008) identified a population of highly obscured AGNs candidates in the entireKs–selected sample, selected on the basis of their very red spectrum (F24µm/F(R) > 1000 and R−Ks > 4.5) (see also Dey et al. 2008).”
Dusty Star Forming Galaxies at High Redshift (2014, unknown): “Fiore et al. (2008) present a similarly selected population of galaxies as DOGs, although they approached the analysis using the fact that all of their targets were 9 Assuming a modified blackbody fit where the optical depth is unity at ∼100 µm. also AGN candidates.”
The Blast Wave Model for AGN Feedback: Effects on AGN Obscuration (2008, background): “In this respect, the observational selection of Compton-thick sources by combining midinfrared to near-infrared and optical photometry of galaxies (Fiore et al. 2008a, 2008b) will provide crucial constraints on the relative role of obscuration and BH depletion in low-mass galactic halos.”
Cosmic X-ray surveys of distant active galaxies (2015, background): “High 24 µm-to-optical flux ratios and red optical/NIR colors (e.g., Fiore et al 2008, 2009; Treister et al 2009a).”
THE SPACE DENSITY OF COMPTON-THICK ACTIVE GALACTIC NUCLEUS AND THE X-RAY BACKGROUND (2009, methodology): “Similarly, Fiore et al. (2008) used a combination of red optical-to-near-IR colors and high 24 µm luminosity to select CT AGN candidates at z∼2.”
A synthesis model for AGN evolution: supermassive black holes growth and feedback modes (2008, result): “2007; Fiore et al. 2008) seem to show quite a good agreement with the predictions of the XRB synthesis models adopted here.”
What drives the growth of black holes (2011, methodology): “…where the absorbing column densities are so high that not even X-ray photons can escape (e.g., Lacy et al., 2004; Stern et al., 2005; Donley et al., 2005, 2008; Alonso-Herrero et al., 2006; Daddi et al., 2007a; Hickox et al., 2007; Fiore et al., 2008, 2009; Bauer et al., 2010; Luo et al., 2011).”
Defining the intrinsic AGN infrared spectral energy distribution and measuring its contribution to the infrared output of composite galaxies (2011, methodology): “…rely on either observed AGN SEDs that likely include considerable amounts of host-galaxy contamin tion at infrared wavelengths or predictions from radiative transfer models which are often poorly constrained (e.g. Polletta et al.2007; Fiore et al. 2008, 2009; Pozzi et al. 2010; Hatziminaoglou etal.”
Faint high-redshift AGN in the Chandra deep field south: the evolution of the AGN luminosity function and black hole demography (2011, background): “At higher redshift, the fraction of Compton thick AGN is more uncertain, but it can be as high as one third of the full AGN population (Fiore et al. 2008, 2009), or even higher (Daddi et al. 2007; Treister et al. 2010).”
OBSCURATION-DEPENDENT EVOLUTION OF ACTIVE GALACTIC NUCLEI (2015, background): “Also, our results are in rough agreement with previous estimates (Fiore et al. 2008; Alexander et al. 2011).”
THE XMM-NEWTON WIDE-FIELD SURVEY IN THE COSMOS FIELD (XMM-COSMOS): DEMOGRAPHY AND MULTIWAVELENGTH PROPERTIES OF OBSCURED AND UNOBSCURED LUMINOUS ACTIVE GALACTIC NUCLEI (2010, background): “Given the high X–ray column density, most of these sources may remain undetected even in the deepest X–ray exposures and their AGN nature can be unvealed only through stacking analysis (Daddi et al. 2007, Fiore et al. 2008, 2009, Lanzuisi et al. 2009).”
THE EVOLUTION OF SWIFT/BAT BLAZARS AND THE ORIGIN OF THE MeV BACKGROUND (2009, methodology): “Generally, given the lack of sufficient signal, the source intrinsic absorption is derived by an hardness-ratio analysis (e.g. Fiore et al. 2008; Brusa et al. 2008).”