J/A+A/694/A241 Identifying CT-AGNs in the COSMOS. I. (Guo+, 2025)
Identifying Compton-thick AGNs in the COSMOS.
I. Among X-ray AGNs with low photon counts.
Guo X., Gu Q., Fang G., Chen Y., Ding N., Yu X., Wang H.
<Astron. Astrophys. 694, A241 (2025)>
=2025A&A...694A.241G 2025A&A...694A.241G (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; X-ray sources
Keywords: galaxies: active - galaxies: nuclei - X-rays: diffuse background -
X-rays: galaxies
Abstract:
Compton-thick active galactic nuclei (CT-AGNs), characterized by a
significant absorption with column densities of
NH≥1.5x1024cm-2, emit feeble X-ray radiation, even undetectable
by X-ray instruments, making them difficult to identify. The X-ray
radiations from AGNs are the predominant origin of the cosmic X-ray
background (CXB). Based on the AGN synthesis models for the CXB, the
fraction of CT-AGNs should constitute a substantial portion,
approximately 30% or more.
The fraction of CT-AGNs discovered in the Cosmological Evolution
Survey (COSMOS) is significantly lower than this value. These mean
that many CT-AGNs may be hidden in AGNs that exhibit low photon counts
or that have not been detected by X-ray instruments. This work focuses
on identifying CT-AGNs hidden in AGNs with low photon counts.
Firstly, we selected 440 AGNs with abundant multiwavelength data as
our sample. Secondly, we analyzed multiwavelength data, extracting
crucial physical parameters required for the CT-AGN diagnosis.
Finally, we used the multiwavelength approaches to identify CT-AGNs.
We have successfully identified 18 CT-AGNs in our sample. Among the
CT-AGNs, four AGNs showed discrepant results across different
diagnostic methods. We discussed the potential reasons behind these
diagnostic discrepancies. We explored the impact of estimating
[OIII]λ5007 luminosities based on [OII]λ3727
luminosities for the CT-AGN diagnosis. We also found that the
properties of host galaxies for CT-AGNs and non-CT-AGNs did not show
significant discrepancies.
Description:
We have used multiwavelength approaches to identify CT-AGNs with low
photon counts in COSMOS. Firstly, we constructed a sample containing
440 AGNs with abundant multiwavelength data.
The table lists physical properties of our AGN sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 125 440 Physical properties of our AGN sample
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See also:
J/ApJ/819/62 : The COSMOS-Legacy Survey (CLS) catalog (Civano+, 2016)
J/ApJ/817/34 : C-COSMOS Legacy sources multiwavelength catalog (Marchesi+ 2016)
J/ApJ/858/77 : DEIMOS 10K spectroscopic survey in COSMOS field (Hasinger+ 2018)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- XID IDs of X-ray sources from the 7Ms catalog,
Civano et al., 2016ApJ...819...62C 2016ApJ...819...62C,
Cat. J/ApJ/819/62
11- 18 F8.4 deg RAdeg Right ascension (J2000) of the X-ray source
from the 7Ms catalog, Civano et al.,
2016ApJ...819...62C 2016ApJ...819...62C, Cat. J/ApJ/819/62
20- 25 F6.4 deg DEdeg Declination (J2000) of the X-ray source
from the 7Ms catalog, Civano et al.,
2016ApJ...819...62C 2016ApJ...819...62C, Cat. J/ApJ/819/62
27- 31 F5.3 --- z Redshift
33- 40 A8 --- f_z Type of redshift, including "spec", "photo"
and "my-photo"
42- 50 A9 --- r_z References of redshift (1)
52 A1 --- l_logLX [<] < for lower limit on logLX
53- 58 F6.3 [10-7W] logLX Log of observed 2-10keV luminosity in
the rest-frame
60- 65 F6.3 [10-7W] logL6um ?=- Log of 6um luminosity for an AGN in
the rest-frame
67- 73 F7.5 --- AlphaAGN ?=- Confidence of AGN components
for SED fitting
75- 80 F6.3 [Msun] logMass ?=- Log of the stellar mass
82- 87 F6.3 [Msun/yr] logSFR ?=- Log of the star formation rate
89- 94 F6.3 [10-7W] logLOIII ?=- Log of [OIII] luminosity
96-100 F5.2 --- SNR-OIII ?=- Signal-to-noise ratio of the [OIII]
emission line
102-107 F6.3 [10-7W] logLOII ?=- Log of [OII] luminosity
109-113 F5.2 --- SNR-OII ?=- Signal-to-noise ratio of the [OII]
emission line
115-120 F6.3 [10-7W] logLNeV ?=- Log of [NeV] luminosity
122-125 F4.2 --- SNR-NeV ?=- Signal-to-noise ratio of the [NeV]
emission line
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Note (1): References of redshift as follows:
H18 = Hasinger et al., 2018ApJ...858...77H 2018ApJ...858...77H, Cat. J/ApJ/858/77
M16 = Marchesi et al., 2016ApJ...817...34M 2016ApJ...817...34M, Cat. J/ApJ/817/34
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Acknowledgements:
Xiaotong Guo, guoxiaotong(at)aqnu.edu.cn
(End) Patricia Vannier [CDS] 17-Jan-2025