Accretion properties of X-ray AGN: Evidence for radiation-regulated obscuration with redshift-dependent host galaxy contribution
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2024
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| author | Laloux, Brivael Georgakakis, Antonis Alexander, David M. Buchner, Johannes Andonie, Carolina Acharya, Nischal Aird, James Alonso-Tetilla, Alba V. Bongiorno, Angela Hickox, Ryan C. Lapi, Andrea Musiimenta, Blessing Almeida, Cristina Ramos Villforth, Carolin Shankar, Francesco |
| author_facet | Laloux, Brivael Georgakakis, Antonis Alexander, David M. Buchner, Johannes Andonie, Carolina Acharya, Nischal Aird, James Alonso-Tetilla, Alba V. Bongiorno, Angela Hickox, Ryan C. Lapi, Andrea Musiimenta, Blessing Almeida, Cristina Ramos Villforth, Carolin Shankar, Francesco |
| contents | We adopt a Bayesian X-ray spectral approach to investigate the accretion properties of unobscured ($20<\log(N_{\rm H}/{\rm cm}^{-2}<22$) and obscured ($22< \log(N_{\rm H}/{\rm cm}^{-2}<24$) active galactic nuclei (AGN) to shed light on the orientation vs evolution scenarios for the origin of the obscuring material. For a sample of 3882 X-ray-selected AGN from the {\it Chandra} COSMOS Legacy, AEGIS and CDFS extragalactic surveys, we constrain their stellar masses, $M_\star$, intrinsic X-ray luminosities, $L_{\rm X}$, obscuring column densities, $N_{\rm H}$, and specific accretion rates $λ\propto L_{\rm X}/M_\star$. 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 $z\approx3$, i.e. the probability of a galaxy with mass $M_\star$ at redshift $z$ hosting an AGN with column density $N_{\rm H}$ 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 $\logλ_{\rm break} \sim-2$ 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 $λ-N_{\rm H}$ 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_07109 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Accretion properties of X-ray AGN: Evidence for radiation-regulated obscuration with redshift-dependent host galaxy contribution Laloux, Brivael Georgakakis, Antonis Alexander, David M. Buchner, Johannes Andonie, Carolina Acharya, Nischal Aird, James Alonso-Tetilla, Alba V. Bongiorno, Angela Hickox, Ryan C. Lapi, Andrea Musiimenta, Blessing Almeida, Cristina Ramos Villforth, Carolin Shankar, Francesco Astrophysics of Galaxies We adopt a Bayesian X-ray spectral approach to investigate the accretion properties of unobscured ($20<\log(N_{\rm H}/{\rm cm}^{-2}<22$) and obscured ($22< \log(N_{\rm H}/{\rm cm}^{-2}<24$) active galactic nuclei (AGN) to shed light on the orientation vs evolution scenarios for the origin of the obscuring material. For a sample of 3882 X-ray-selected AGN from the {\it Chandra} COSMOS Legacy, AEGIS and CDFS extragalactic surveys, we constrain their stellar masses, $M_\star$, intrinsic X-ray luminosities, $L_{\rm X}$, obscuring column densities, $N_{\rm H}$, and specific accretion rates $λ\propto L_{\rm X}/M_\star$. 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 $z\approx3$, i.e. the probability of a galaxy with mass $M_\star$ at redshift $z$ hosting an AGN with column density $N_{\rm H}$ 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 $\logλ_{\rm break} \sim-2$ 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 $λ-N_{\rm H}$ 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. |
| title | Accretion properties of X-ray AGN: Evidence for radiation-regulated obscuration with redshift-dependent host galaxy contribution |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2403.07109 |