Deepest view of AGN X-ray variability with the 7 Ms Chandra Deep Field-South survey
| Autor: | Maurizio Paolillo, W. N. Brandt, Junyao Li, T. M. Hughes, Mouyuan Sun, Guang Yang, Yongquan Xue, Fabio Vito, Franz E. Bauer, X. C. Zheng, Birong Luo, Shifu Zhu, Teng Liu, Xinwen Shu, Junxian Wang, Cristian Vignali |
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| Přispěvatelé: | Zheng, X. C., Xue, Y. Q., Brandt, W. N., Li, J. Y., Paolillo, M., Yang, G., Zhu, S. F., Luo, B., Sun, M. Y., Hughes, T. M., Bauer, F. E., Vito, F., Wang, J. X., Liu, T., Vignali, C., Shu, X. W. |
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Active galactic nucleus
Cosmology and Nongalactic Astrophysics (astro-ph.CO) Astrophysics::High Energy Astrophysical Phenomena galaxies: active FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Type (model theory) 01 natural sciences Luminosity galaxies: high-redshift 0103 physical sciences quasars: supermassive black hole Xrays: bursts 010303 astronomy & astrophysics Physics High Energy Astrophysical Phenomena (astro-ph.HE) 010308 nuclear & particles physics Spectral density Order (ring theory) Astronomy and Astrophysics Astronomy and Astrophysic Light curve Xrays: burst Astrophysics - Astrophysics of Galaxies Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Chandra Deep Field South galaxies: nuclei Astrophysics - High Energy Astrophysical Phenomena Energy (signal processing) X-rays: galaxie Astrophysics - Cosmology and Nongalactic Astrophysics |
| Zdroj: | NASA Astrophysics Data System |
| Popis: | We systematically analyze X-ray variability of active galactic nuclei (AGNs) in the 7~Ms \textit{Chandra} Deep Field-South survey. On the longest timescale ($\approx~17$ years), we find only weak (if any) dependence of X-ray variability amplitudes on energy bands or obscuration. We use four different power spectral density (PSD) models to fit the anti-correlation between normalized excess variance ($\sigma^2_{\rm nxv}$) and luminosity, and obtain a best-fit power law index $\beta=1.16^{+0.05}_{-0.05}$ for the low-frequency part of AGN PSD. We also divide the whole light curves into 4 epochs in order to inspect the dependence of $\sigma^2_{\rm nxv}$ on these timescales, finding an overall increasing trend. The analysis of these shorter light curves also infers a $\beta$ of $\sim 1.3$ that is consistent with the above-derived $\beta$, which is larger than the frequently-assumed value of $\beta=1$. We then investigate the evolution of $\sigma^2_{\rm nxv}$. No definitive conclusion is reached due to limited source statistics but, if present, the observed trend goes in the direction of decreasing AGN variability at fixed luminosity toward large redshifts. We also search for transient events and find 6 notable candidate events with our considered criteria. Two of them may be a new type of fast transient events, one of which is reported here for the first time. We therefore estimate a rate of fast outbursts $\langle\dot{N}\rangle = 1.0^{+1.1}_{-0.7}\times 10^{-3}~\rm galaxy^{-1}~yr^{-1}$ and a tidal disruption event~(TDE) rate $\langle\dot{N}_{\rm TDE}\rangle=8.6^{+8.5}_{-4.9}\times 10^{-5}~\rm galaxy^{-1}~yr^{-1}$ assuming the other four long outbursts to be TDEs. Comment: 20 pages, 16 figures. Accepted for publication in ApJ |
| Databáze: | OpenAIRE |
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