The WISSH Quasars Project III. X-ray properties of hyper-luminous quasars

S. Martocchia; E. Piconcelli; L. Zappacosta; F. Duras; G. Vietri; C. Vignali; S. Bianchi; M. Bischetti; A. Bongiorno; M. Brusa; G. Lanzuisi; A. Marconi; S. Mathur; G. Miniutti; F. Nicastro; G. Bruni; F. Fiore

doi:10.1051/0004-6361/201731314

paper

The WISSH Quasars Project III. X-ray properties of hyper-luminous quasars

arXiv:1708.00452 · doi:10.1051/0004-6361/201731314

Abstract

We perform a survey of the X-ray properties of 41 objects from the WISE/SDSS selected Hyper-luminous (WISSH) quasars sample, composed by 86 broad-line quasars (QSOs) with bolometric luminosity $L_{B o l} \geq 2 \times 1 0^{47} er g s^{- 1}$ , at z~2-4. All but 3 QSOs show unabsorbed 2-10 keV luminosities $L_{2 - 10} \geq 1 0^{45} er g s^{- 1}$ . Thanks to their extreme radiative output across the Mid-IR-to-X-ray range, WISSH QSOs offer the opportunity to significantly extend and validate the existing relations involving $L_{2 - 10}$ . We study $L_{2 - 10}$ as a function of (i) X-ray-to-Optical (X/O) flux ratio, (ii) mid-IR luminosity ( $L_{M I R}$ ), (iii) $L_{B o l}$ as well as (iv) $α_{O X}$ vs. the 2500 $A ˚$ luminosity. We find that WISSH QSOs show very low X/O(<0.1) compared to typical AGN values; $L_{2 - 10} / L_{M I R}$ ratios significantly smaller than those derived for AGN with lower luminosity; large X-ray bolometric corrections $k_{Bol, X} \sim$ 100-1000; and steep $- 2 < α_{O X} < - 1.7$ . These results lead to a scenario where the X-ray emission of hyper-luminous quasars is relatively weaker compared to lower-luminosity AGN. Models predict that such an X-ray weakness can be relevant for the acceleration of powerful high-ionization emission line-driven winds, commonly detected in the UV spectra of WISSH QSOs, which can in turn perturb the X-ray corona and weaken its emission. Accordingly, hyper-luminous QSOs represent the ideal laboratory to study the link between the AGN energy output and wind acceleration. Additionally, WISSH QSOs show very large BH masses ( $lo g [M_{BH} / M_{⊙}]$ >9.5). This enables a more robust modeling of the $Γ - M_{B H}$ relation by increasing the statistics at high masses. We derive a flatter $Γ$ dependence than previously found over the broad range 5 < $lo g (M_{BH} / M_{⊙})$ < 11.

20 pages, 14 Figures. Accepted for publication on A&A

The WISSH Quasars Project III. X-ray properties of hyper-luminous quasars

Abstract

References in corpus (30)

Cited by in corpus (50)