X-ray spectroscopic survey of highly-accreting AGN
| Autor: | Laurenti, M., Piconcelli, E., Zappacosta, L., Tombesi, F., Vignali, C., Bianchi, S., Marziani, P., Vagnetti, F., Bongiorno, A., Bischetti, M., del Olmo, A., Lanzuisi, G., Luminari, A., Middei, R., Perri, M., Ricci, C., Vietri, G. |
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| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | A&A 657, A57 (2022) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/202141829 |
| Popis: | Improving our understanding of the nuclear properties of high-Eddington ratio ($\lambda_\mathrm{Edd}$) active galactic nuclei (AGN) is necessary since the bulk of X-ray spectroscopic studies have been focused on low-Eddington AGN. We present here the X-ray spectral analysis of 14 radio-quiet, $\lambda_\mathrm{Edd}\gtrsim1$ AGN at $0.4\leq z \leq 0.75$, observed with XMM-Newton. Optical/UV data from simultaneous Optical Monitor observations have been also considered. These AGN have been selected to have relatively high values of black hole mass ($M_\mathrm{BH}\sim10^{8-8.5}M_\odot$) and bolometric luminosity ($L_\mathrm{bol} \sim 10^{46}$ erg s$^{-1}$), in order to complement previous studies of high-Eddington AGN at lower $M_\mathrm{BH}$ and $L_\mathrm{bol}$. We studied the relation between $\lambda_\mathrm{Edd}$ and other key X-ray spectral parameters, such as the photon index of the power-law continuum $\Gamma$, the X-ray bolometric correction $k_\mathrm{bol,X}$ and $\alpha_\mathrm{ox}$. Despite the homogeneous optical and SMBH accretion properties, the X-ray properties of these high-Eddington AGN are quite heterogeneous. We measured values of $\Gamma$ comprised between 1.3 and 2.5, at odds with the expectations based on previously reported $\Gamma-\lambda_\mathrm{Edd}$ relations, by which $\Gamma\geq2$ would be an ubiquitous hallmark of AGN with $\lambda_\mathrm{Edd}\sim1$. We found that $\sim30\%$ of the sources are X-ray weak, with an X-ray emission about a factor of $\sim10-80$ fainter than that of typical AGN at similar UV luminosities. The X-ray weakness seems to be intrinsic and not due to intervening obscuration. This may indicate that high-Eddington AGN commonly undergo periods of intrinsic X-ray weakness. Furthermore, results from a follow-up monitoring with Swift of one of these X-ray weak AGN suggest that these periods can last for several years. Comment: 17 pages, 8 figures (with 2 more figures in Appendix A and B). Accepted for publication in A&A |
| Databáze: | arXiv |
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