A Large Population of Luminous Active Galactic Nuclei Lacking X-ray Detections: Evidence for Heavy Obscuration?

Abstract

We present a large sample of infrared-luminous candidate active galactic nuclei (AGNs) that lack X-ray detections in Chandra, XMM-Newton, and NuSTAR fields. We selected all optically detected SDSS sources with redshift measurements, combined additional broadband photometry from WISE, UKIDSS, 2MASS, and GALEX, and modeled the spectral energy distributions (SEDs) of our sample sources. We parameterize nuclear obscuration in our SEDs with $E(B-V{)}_{\text{AGN}}$ and uncover thousands of powerful obscured AGNs that lack X-ray counterparts, many of which are identified as AGN candidates based on straightforward WISE photometric criteria. Using the observed luminosity correlation between restframe 2-10 keV ($L_{\text{X}}$) and restframe AGN 6 $\mu \text{m}$ ($L_{\text{MIR}}$), we estimate the intrinsic X-ray luminosities of our sample sources and combine these data with flux limits from X-ray catalogs to determine lower limits on nuclear obscuration. Using the ratio of intrinsic-to-observed X-ray luminosity ($R_{L_{\text{X}}}$), we find a significant fraction of sources with column densities approaching $N_{\text{H}}>$ 10${}^{\text{24}}$ cm${}^{-\text{2}}$, suggesting that multiwavelength observations are necessary to account for the population of heavily obscured AGNs. We simulate the underlying $N_{\text{H}}$ distribution for the X-ray non-detected sources in our sample through survival analysis, and confirm the presence of AGN activity via X-ray stacking. Our results point to a considerable population of extremely obscured AGNs undetected by current X-ray observatories.

arXiv comment15 pages, 6 tables, 10 figures. Accepted to ApJ. For the associated catalogs (tables 3 and 4), see http://dartgo.org/ccarroll_xagn_cat

References in corpus (48)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Sloan Digital Sky Survey: Technical Summary
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Mid-Infrared Selection of Active Galaxies
• Active Galactic Nuclei: what's in a name?
• The Chandra Source Catalog
• Obscured Active Galactic Nuclei
• Revised Catalog of GALEX Ultraviolet Sources. I. The All-sky Survey: GUVcat_AIS
• The Masses of Nuclear Black Holes in Luminous Elliptical Galaxies and Implications for the Space Density of the Most Massive Black Holes
• The XMM-Newton serendipitous survey. VII. The third XMM-Newton serendipitous source catalogue
• unWISE: unblurred coadds of the WISE imaging
• Resolving the mid-infrared cores of local Seyferts
• Low Resolution Spectral Templates For AGNs and Galaxies From 0.03 -- 30 microns
• A synthesis model for AGN evolution: supermassive black holes growth and feedback modes
• Space density of optically-selected type 2 quasars
• The WISE AGN Catalog
• Starburst-like Dust Extinction in the Small Magellanic Cloud
• Chasing highly obscured QSOs in the COSMOS field
• New Spectral Model for Constraining Torus Covering Factors from Broadband X-ray Spectra of Active Galactic Nuclei
• A correlation between star formation rate and average black hole accretion in star forming galaxies
• Photometric redshifts for the SDSS Data Release 12
• AGES: The AGN and Galaxy Evolution Survey
• The Accretion History of AGN I: Supermassive Black Hole Population Synthesis Model
• The role of star-formation and AGN in dust heating of z = 0.3-2.8 galaxies - I. Evolution with redshift and luminosity
• The X-Ray to Mid-Infrared Relation of AGN at High Luminosity
• A large population of mid-infrared selected, obscured active galaxies in the Bootes field
• X-ray Binary Luminosity Function Scaling Relations for Local Galaxies Based on Subgalactic Modeling
• The Spitzer mid-infrared AGN survey. I - optical and near-infrared spectroscopy of candidate obscured and normal AGN selected in the mid-infrared
• NuSTAR Reveals Extreme Absorption in z < 0.5 Type 2 Quasars
• The NuSTAR Extragalactic Surveys: Overview and Catalog from the COSMOS Field
• The Angular Clustering of Infrared-Selected Obscured and Unobscured Quasars
• Spectroscopic Identification of Type 2 Quasars at Z < 1 in SDSS-III/BOSS
• Mass without radiation: heavily obscured AGN, the X-ray Background and the Black Hole Mass Density
• The X-ray and Mid-Infrared luminosities in Luminous Type 1 Quasars
• Crossing the Line: Active Galactic Nuclei in the Star-forming region of the BPT Diagram
• The NuSTAR Serendipitous Survey: Hunting for The Most Extreme Obscured AGN at >10 keV
• SDSS-IV eBOSS Spectroscopy of X-ray and WISE AGN in Stripe 82X: Overview of the Demographics of X-ray and Mid-Infrared Selected Active Galactic Nuclei
• Weighing obscured and unobscured quasar hosts with the CMB
• A Large Population of Obscured AGN in Disguise as Low Luminosity AGN in Chandra Deep Field South
• Galaxy-scale Bars in Late-type Sloan Digital Sky Survey Galaxies Do Not Influence the Average Accretion Rates of Supermassive Black Holes
• Low-luminosity AGN and X-ray binary populations in COSMOS star-forming galaxies
• The NuSTAR Extragalactic Surveys: source catalog and the Compton-thick fraction in the UDS field
• A Spectroscopic Survey of WISE-selected Obscured Quasars with the Southern African Large Telescope
• NuSTAR and Keck Observations of Heavily Obscured Quasars Selected by WISE

Cited by in corpus (18)

• CEERS Key Paper VI: JWST/MIRI Uncovers a Large Population of Obscured AGN at High Redshifts
• AGN Selection and Demographics in GOODS-S/HUDF from X-ray to Radio
• Compton-Thick AGN in the NuSTAR era VI: The observed Compton-thick fraction in the Local Universe
• Infrared Spectral Energy Distribution and Variability of Active Galactic Nuclei: Clues to the Structure of Circumnuclear Material
• The eROSITA Final Equatorial-Depth Survey (eFEDS): A multiwavelength view of WISE mid-infrared galaxies/active galactic nuclei
• A Catalog of Host Galaxies for WISE-Selected AGN: Connecting Host Properties with Nuclear Activity and Identifying Contaminants
• BAT AGN Spectroscopic Survey-XXIII. A New Mid-Infrared Diagnostic for Absorption in Active Galactic Nuclei
• A High Fraction of Heavily X-ray Obscured Active Galactic Nuclei
• Variable AGN in the GALEX Time Domain Survey
• Chandra Observations of Excess Fe K$\alpha$ Line Emission in Galaxies with High Star Formation Rates: X-ray Reflection on Galaxy Scales?
• Identifying type II quasars at intermediate redshift with few-shot learning photometric classification
• Black hole-galaxy co-evolution and the role of feedback
• X-ray Analysis of AGN from the GALEX Time Domain Survey
• pop-cosmos: Insights from generative modeling of a deep, infrared-selected galaxy population
• Exploring the physical properties of Type II Quasar candidates at intermediate redshifts with CIGALE
• Identifying Compton-thick active galactic nuclei in the COSMOS. II. Searching among mid-infrared selected AGNs
• pop-cosmos: Star formation over 12 Gyr from generative modelling of a deep infrared-selected galaxy catalogue
• BASS XXX: Distribution Functions of DR2 Eddington-ratios, Black Hole Masses, and X-ray Luminosities