J/ApJ/802/89 Luminosity function of X-ray-selected AGNs (Buchner+, 2015)
Obscuration-dependent evolution of active galactic nuclei.
Buchner J., Georgakakis A., Nandra K., Brightman M., Menzel M.-L., Liu Z.,
Hsu L.-T., Salvato M., Rangel C., Aird J., Merloni A., Ross N.
<Astrophys. J., 802, 89 (2015)>
=2015ApJ...802...89B 2015ApJ...802...89B
ADC_Keywords: Redshifts ; Active gal. nuclei ; Surveys ; X-ray sources
Keywords: galaxies: active; quasars: supermassive black holes; surveys;
X-rays: galaxies
Abstract:
We aim to constrain the evolution of active galactic nuclei (AGNs) as
a function of obscuration using an X-ray-selected sample of ∼2000 AGNs
from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS, and
XMM-XXL fields. The spectra of individual X-ray sources are analyzed
using a Bayesian methodology with a physically realistic model to
infer the posterior distribution of the hydrogen column density and
intrinsic X-ray luminosity. We develop a novel non-parametric method
that allows us to robustly infer the distribution of the AGN
population in X-ray luminosity, redshift, and obscuring column
density, relying only on minimal smoothness assumptions. Our analysis
properly incorporates uncertainties from low count spectra,
photometric redshift measurements, association incompleteness, and the
limited sample size. We find that obscured AGNs with NH>1022/cm2
account for 77-5+4% of the number density and luminosity density
of the accretion supermassive black hole population with
LX>1043erg/s, averaged over cosmic time. Compton-thick AGNs
account for approximately half the number and luminosity density of
the obscured population, and 38-7+8% of the total. We also find
evidence that the evolution is obscuration dependent, with the
strongest evolution around NH~1023/cm2. We highlight this
by measuring the obscured fraction in Compton-thin AGNs, which
increases toward z∼3, where it is 25% higher than the local value. In
contrast, the fraction of Compton-thick AGNs is consistent with being
constant at ~35%, independent of redshift and accretion
luminosity. We discuss our findings in the context of existing models
and conclude that the observed evolution is, to first order, a side
effect of anti-hierarchical growth.
Description:
We combined deep and shallow, wide-area X-ray surveys conducted by
Chandra and XMM-Newton (including Chandra Deep Field South (CDFS; Xue
et al. 2011, J/ApJS/195/10), the All Wavelength Extended Groth strip
International Survey (AEGIS; Davis et al. 2007ApJ...660L...1D 2007ApJ...660L...1D), the
Cosmological evolution Survey (COSMOS, Scoville et al.
2007ApJS..172....1S 2007ApJS..172....1S), and the equatorial region of the XMM-XXL survey
(PI: Pierre)) to constrain the space density of X-ray-selected AGNs as
a function of accretion luminosity, obscuring column density, and
redshift.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 41 780 Space density estimates as a function of luminosity,
redshift and obscuration
figure4.dat 33 130 Total AGN Intrinsic 2-10keV Luminosity function,
including Compton-thick
figure7.dat 57 30 Obscured and Compton-thick fractions as a function
of luminosity and redshift
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 [10+7W] logL0 [42/46] Lower edge of model luminosity bin (G1)
6- 9 F4.1 [10+7W] logL1 [42/46] Upper edge of model luminosity bin (G1)
11- 13 F3.1 --- z0 [0/4] Lower edge of model redshift bin
15- 17 F3.1 --- z1 [0.1/7] Upper edge of model redshift bin
19- 22 F4.1 [cm-2] logNH0 [20/24] Lower edge of model neutral hydrogen
equivalent column density bin (G1)
24- 27 F4.1 [cm-2] logNH1 [21/26] Upper edge of model neutral hydrogen
equivalent column density bin (G1)
29- 34 F6.3 [Mpc-3] logphi0 [-9.2/-4.1] The 10% quantile of space density
posterior (2)
36- 41 F6.3 [Mpc-3] logphi1 [-7.1/-3.3] The 90% quantile of space density
posterior (2)
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Note (2): The density of AGN was estimated across both priors, as adopted
throughout the paper. In logarithmic units.
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Byte-by-byte Description of file: figure4.dat
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Bytes Format Units Label Explanations
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1- 4 F4.2 --- z0 [0/4] Lower edge of redshift bin
6- 9 F4.2 --- z1 [0.1/7] Upper edge of redshift bin
11- 14 F4.1 [10+7W] logL0 [42/46] Lower edge of luminosity bin (G1)
16- 19 F4.1 [10+7W] logL1 [42/46] Upper edge of luminosity bin (G1)
21- 26 F6.3 [Mpc-3] logphilo 10% quantile of the posterior of the space
density (G1)
28- 33 F6.3 [Mpc-3] logphihi 90% quantile of the posterior of the space
density (G1)
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Byte-by-byte Description of file: figure7.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 [10+7W] logL0 [42/46] Lower edge of luminosity bin (G1)
6- 9 F4.1 [10+7W] logL1 [42/46] Upper edge of luminosity bin (G1)
11- 13 F3.1 --- z0 [0/4] Lower edge of redshift bin
15- 17 F3.1 --- z1 [0.1/7] Upper edge of redshift bin
19- 22 F4.2 --- obscflo [0/1] Compton-thin obscured fraction
10% quantile
24- 27 F4.2 --- obscfhi [0/1] Compton-thin obscured fraction
90% quantile
29- 32 F4.2 --- obscfpch [0/1] Compton-thin constant-value estimate
34- 37 F4.2 --- obscfpcs [0/1] Compton-thin obscured fraction
constant-slope estimate
39- 42 F4.2 --- CTKflo [0/1] Compton-thick fraction 10% quantile
44- 47 F4.2 --- CTKfhi [0/1] Compton-thick fraction 90% quantile
49- 52 F4.2 --- CTKfpch [0/1] Compton-thick fraction
constant-value estimate
54- 57 F4.2 --- CTKfpcs [0/1] Compton-thick fraction
constant-slope estimate
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Global notes:
Note (G1): In logarithmic units.
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History:
* 27-Aug-2015: From electronic version of the journal
* 18-Oct-2017: figure4 and figure7 added, from author
(Johannes Buxhner, jbuchner(at)astro.puc.cl)
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Jul-2015