J/ApJ/908/185 X-Ray luminosities for ∼41000 AGNs (Carroll+, 2021)
A Large Population of Luminous Active Galactic Nuclei Lacking X-Ray Detections:
Evidence for Heavy Obscuration?
Carroll C.M., Hickox R.C., Masini A., Lanz L., Assef R.J., Stern D.,
Chen C.-T.J., Ananna T.T.
<Astrophys. J., 908, 185 (2021)>
=2021ApJ...908..185C 2021ApJ...908..185C
ADC_Keywords: X-ray sources; Infrared; Active gal. nuclei; QSOs; Redshifts
Keywords: Active galaxies ; Infrared galaxies ; Quasars ; Surveys
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)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 rest-frame 2-10 keV (LX) and
rest-frame AGN 6um (LMIR), 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
(RLX), we find a significant fraction of sources with column
densities approaching NH>1024/cm2, suggesting that
multiwavelength observations are necessary to account for the
population of heavily obscured AGNs. We simulate the underlying NH
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.
Description:
The sample described in this paper consists of 40935 optically
detected sources by the Sloan Digital Sky Survey (SDSS), matched to
sources detected by the Wide-field Infrared Survey Explorer (WISE),
that co-exist within one or more of our X-ray data sets, consisting of
the archives and survey fields of the Chandra, XMM, and NuSTAR
observatories.
The sample is comprised of sources observed by one or more of the
following X-ray observatories: Chandra, XMM, or NuSTAR. In this work,
we utilized five X-ray survey data sets: the Chandra Source Catalog 2
(CSC2), the 3XMM-DR8 catalog, and the combined NuSTAR catalogs of
COSMOS and UDS, as well as the NuSTAR serendipitous survey (SSC). For
an X-ray observation to be considered, the specific observation must
be included in one of the five X-ray survey data sets used in this
work.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 123 40935 Source positions and X-ray luminosity estimates by
observatory
table4.dat 121 40935 SED modeling output parameters.
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See also:
IX/45 : The Chandra Source Catalog, Release 1.1 (Evans+ 2012)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/335 : Catalog of GALEX UV sources (GUVcat_AIS GR6+7) (Bianchi+ 2017)
IX/55 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR8 (XMM-SSC, 2018)
IX/57 : The Chandra Source Catalog (CSC), Release 2.0 (Evans+, 2019)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/662/808 : Cusp radius in luminous elliptical galaxies (Lauer+, 2007)
J/AJ/136/2373 : Type 2 quasars from SDSS (Reyes+, 2008)
J/ApJ/713/970 : Low-resolution SED templates for AGNs & galaxies (Assef+, 2010)
J/ApJS/200/8 : AGES; the AGN and Galaxy Evolution Survey (Kochanek+, 2012)
J/ApJS/208/24 : Spitzer MIR AGN survey. I. (Lacy+, 2013)
J/ApJ/808/185 : NuSTAR surveys; COSMOS catalog (Civano+, 2015)
J/ApJ/807/129 : X-ray to MIR luminosities relation of AGNs (Stern, 2015)
J/ApJS/234/23 : The WISE AGN candidates catalogs (Assef+, 2018)
J/ApJ/865/43 : Xray stacking analysis of Chandra-COSMOS gal (Fornasini+, 2018)
J/ApJS/235/17 : NuSTAR Extragalactic Surveys; UDS field (Masini+, 2018)
J/ApJ/876/50 : Xray & MIR AGNs Stripe 82 with eBOSS spectra (LaMassa+, 2019)
J/ApJS/243/3 : Chandra observations of SINGS galaxies (Lehmer+, 2019)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- SDSS SDSS ObjID
21- 32 F12.8 deg RAdeg [0/360] Right Ascension in degrees (J2000)
34- 47 F14.10 deg DEdeg [-22/82] Declination in degrees (J2000)
49- 49 A1 --- l_Lxcha Upper limit flag for Chandra source
51- 60 E10.4 W Lxcha ?=0.0000e+00 X-ray luminosity for Chandra source
62- 71 E10.4 W e_Lxcha ?=0.0000e+00 X-ray luminosity error for Chandra
source
73- 73 A1 --- l_Lxxmm Upper limit flag for XMM source
75- 84 E10.4 W Lxxmm ?=0.0000e+00 X-ray luminosity for XMM source
86- 95 E10.4 W e_Lxxmm ?=0.0000e+00 X-ray luminosity error for XMM
source
97- 97 A1 --- l_Lxnst Upper limit flag for NuSTAR source
99-108 E10.4 W Lxnst ?=0.0000e+00 X-ray luminosity for NuSTAR source
110-119 E10.4 W e_Lxnst ?=0.0000e+00 X-ray luminosity error for NuSTAR
source
121-123 A3 --- Field Final X-ray field used for analysis (1)
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Note (1): Column 13 (field); Final X-ray field used for analysis is
blank if not used.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.3 --- z [0/0.8] Redshift (1)
7- 11 F5.3 --- e_z [0/0.5] Redshift error
13- 17 F5.2 --- (B-V) [0/50.1] Color excess (1)
19- 23 F5.2 --- e_(B-V) [0/51] Color excess error (2)
25- 37 E13.7 --- cAGN [5e-19/4e-14]?=0.0000000e+00 AGN template
normalization (1)
39- 51 E13.7 --- cell [1e-20/2.9e-13]?=0.0000000e+00 Elliptical
template normalization (1)
53- 65 E13.7 --- cSFG [4e-20/2e-13]?=0.0000000e+00 Star-forming
template normalization (1)
67- 79 E13.7 --- cIRR [9e-20/9e-14]?=0.0000000e+00 Irregular/starburst
template normalization (1)
81- 90 F10.2 --- chi2 [0.14/9692874] Chi-squared (1)
92- 93 I2 --- dchi2 [2/12] Degrees of Freedom
95- 97 I3 % pAGN [0/100] Percent of realisations with AGN (3)
99-108 E10.4 W LIR ?=0.0000e+00 AGN 6um IR luminosity (1)
110-119 E10.4 W e_LIR ?=0.0000e+00 AGN 6um IR luminosity error (2)
121-121 I1 --- wiseAGN [0/1] WISE AGN flag (0=false, 1=true)
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Note (1): Modeling output parameters.
Note (2): Uncertainties on ebv and lir were estimated via the median absolute
deviation of all source realisations containing AGN contribution.
Note (3): Column 11 (pAGN): Percent of realisations out of 1000 with cAGN>0.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 26-Feb-2024