J/MNRAS/471/364 Spectral curvature values for AGN sample (Baronchelli+, 2017)
Inferring Compton-thick AGN candidates at z > 2 with Chandra using the >8 keV
rest-frame spectral curvature.
Baronchelli L., Koss M., Schawinski K., Cardamone C., Civano F.,
Comastri A., Elvis M., Lanzuisi G., Marchesi S., Ricci C., Salvato M.,
Trakhtenbrot B., Treister E.
<Mon. Not. R. Astron. Soc., 471, 364-372 (2017)>
=2017MNRAS.471..364B 2017MNRAS.471..364B (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Redshifts ; X-ray sources
Keywords: galaxies: active - galaxies: high-redshift - galaxies: Seyfert -
X-rays: galaxies
Abstract:
To fully understand cosmic black hole growth, we need to constrain the
population of heavily obscured active galactic nuclei (AGNs) at the
peak of cosmic black hole growth (z∼1-3). Sources with obscuring
column densities higher than 1024atoms/cm2, called Compton-thick
(CT) AGNs, can be identified by excess X-ray emission at ∼20-30keV,
called the 'Compton hump'. We apply the recently developed Spectral
Curvature (SC) method to high-redshift AGNs (2<z<5) detected with
Chandra. This method parametrizes the characteristic 'Compton hump'
feature cosmologically redshifted into the X-ray band at observed
energies <10 keV. We find good agreement in CT AGNs found using the SC
method, and bright sources fit using their full spectrum with X-ray
spectroscopy. In the Chandra Deep Field-South, we measure a CT
fraction of 17+19-11% (3/17) for sources with observed luminosity
>5x1043erg/s. In the Cosmological Evolution Survey (COSMOS), we find
an observed CT fraction of 15+4-3% (40/272) or 32±11 per cent
when corrected for the survey sensitivity. When comparing to low
redshift AGNs with similar X-ray luminosities, our results imply that
the CT AGN fraction is consistent with having no redshift evolution.
Finally, we provide SC equations that can be used to find
high-redshift CT AGNs (z>1) for current (XMM-Newton) and future
(eROSITA and ATHENA) X-ray missions.
Description:
We extend the Spectral Curvature (SC) method to high-redshift (z>2)
AGNs where the rest-frame Compton hump feature can be observed with
Chandra. We applied the SC method to deep Chandra observations. Thanks
to the high sensitivity of Chandra, we can find Compton-thick
candidates even at redshift higher than 2. The deepest Chandra surveys
are the CDF-S and the COSMOS legacy survey.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 63 271 Spectral curvature values for the analysed
sample in the COSMOS legacy survey
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See also:
J/ApJ/817/34 : C-COSMOS Legacy sources multiwavelength catalog (Marchesi+ 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- ID Identification number of the source, from
the COSMOS legacy survey (Marchesi et al.
2016, Cat. J/ApJ/817/34)
11- 14 F4.2 --- z Spectroscopic redshift from Marchesi et al.
(2016, Cat. J/ApJ/817/34)
16- 18 I3 ct soft Number of counts in the soft energy
range [8-12]/(1+z)keV
20- 21 I2 ct e_soft rms uncertainty on soft
23- 24 I2 ct mid Number of counts in the mid energy
range [12-16]/(1+z)keV
26 I1 ct e_mid rms uncertainty on soft
28- 29 I2 ct hard Number of counts in the hard energy
range [16-24]/(1+z)keV
31 I1 ct e_hard rms uncertainty on soft
33- 35 I3 ct tot Number of counts in the total energy
range [8-24]/(1+z)keV
37- 38 I2 ct e_tot rms uncertainty on soft
40- 44 F5.2 --- SC Measured Spectral Curvature values
46- 49 F4.2 --- e_SC rms uncertainty on SC
51- 56 F6.2 10+22cm-2 NH1 ?=-99 Column density from Marchesi et al.
(2016, Cat. J/ApJ/817/34) estimated
using a hardness ratio (1022atom/cm2)
58- 63 F6.2 10+22cm-2 NH2 ?=-99 Column density estimated from
Marchesi et al. (2016ApJ...830..100M 2016ApJ...830..100M)
spectral fitting (1022atom/cm2)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-May-2020