TY - JOUR
T1 - Accretion properties of X-ray AGN: evidence for radiation-regulated obscuration with redshift-dependent host galaxy contribution
AU - Laloux, Brivael
AU - Georgakakis, Antonis
AU - Alexander, David M.
AU - Buchner, Johannes
AU - Andonie, Carolina
AU - Acharya, Nischal
AU - Aird, James
AU - Alonso-Tetilla, Alba V.
AU - Bongiorno, Angela
AU - Hickox, Ryan C.
AU - Lapi, Andrea
AU - Musiimenta, Blessing
AU - Almeida, Cristina Ramos
AU - Vellforth, Carolin
AU - Shankar, Francesco
N1 - Submitted to MNRAS
PY - 2024/8/1
Y1 - 2024/8/1
N2 - We adopt a Bayesian X-ray spectral approach to investigate the accretion properties of unobscured (20 < log(NH /cm−2 < 22) and obscured (22 < log(NH /cm−2 < 24) active galactic nuclei (AGNs) to shed light on the orientation versus evolution scenarios for the origin of the obscuring material. For a sample of 3882 X-ray-selected AGN from the Chandra COSMOS Legacy, AEGIS, and CDFS extragalactic surveys, we constrain their stellar masses, M , intrinsic X-ray luminosities, LX , obscuring column densities, NH , and specific accretion rates λ ∝ LX /M . By combining these observables within a Bayesian non-parametric approach, we infer, for the first time, the specific accretion rate distribution (SARD) of obscured and unobscured AGN to z ≈ 3, i.e. the probability of a galaxy with mass M at redshift z hosting an AGN with column density NH and specific accretion rate λ. Our findings indicate that (1) both obscured and unobscured SARDs share similar shapes, shifting towards higher accretion rates with redshift, (2) unobscured SARDs exhibit a systematic offset towards higher λ compared to obscured SARD for all redshift intervals, (3) the obscured AGN fraction declines sharply at log λbreak ∼ −2 for z < 0.5, but shifts to higher λ values with increasing redshift, (4) the incidence of AGN within the theoretically unstable blow-out region of the λ − NH plane increases with redshift. These observations provide compelling evidence for AGN ‘downsizing’ and radiation-regulated nuclear-scale obscuration with an increasing host galaxy contribution towards higher redshifts.
AB - We adopt a Bayesian X-ray spectral approach to investigate the accretion properties of unobscured (20 < log(NH /cm−2 < 22) and obscured (22 < log(NH /cm−2 < 24) active galactic nuclei (AGNs) to shed light on the orientation versus evolution scenarios for the origin of the obscuring material. For a sample of 3882 X-ray-selected AGN from the Chandra COSMOS Legacy, AEGIS, and CDFS extragalactic surveys, we constrain their stellar masses, M , intrinsic X-ray luminosities, LX , obscuring column densities, NH , and specific accretion rates λ ∝ LX /M . By combining these observables within a Bayesian non-parametric approach, we infer, for the first time, the specific accretion rate distribution (SARD) of obscured and unobscured AGN to z ≈ 3, i.e. the probability of a galaxy with mass M at redshift z hosting an AGN with column density NH and specific accretion rate λ. Our findings indicate that (1) both obscured and unobscured SARDs share similar shapes, shifting towards higher accretion rates with redshift, (2) unobscured SARDs exhibit a systematic offset towards higher λ compared to obscured SARD for all redshift intervals, (3) the obscured AGN fraction declines sharply at log λbreak ∼ −2 for z < 0.5, but shifts to higher λ values with increasing redshift, (4) the incidence of AGN within the theoretically unstable blow-out region of the λ − NH plane increases with redshift. These observations provide compelling evidence for AGN ‘downsizing’ and radiation-regulated nuclear-scale obscuration with an increasing host galaxy contribution towards higher redshifts.
KW - galaxies: active
KW - X-rays: galaxies - infrared
KW - galaxies
U2 - 10.1093/mnras/stae1649
DO - 10.1093/mnras/stae1649
M3 - Article
SN - 0035-8711
VL - 532
SP - 3459
EP - 3479
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -