X-ray View of Hyper-Luminous Quasars at z = 2 ~ 4: the WISSH project

Degli Agosti, Cecilia (2023) X-ray View of Hyper-Luminous Quasars at z = 2 ~ 4: the WISSH project. [Laurea magistrale], Università di Bologna, Corso di Studio in Astrofisica e cosmologia [LM-DM270]
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Abstract

At the cosmic noon (z≈2-4), hyper-luminous quasars (HyLQSOs) shine at L_bol>10^47 erg/s and the most energetic multiphase winds are predicted to be ejected. These are the most efficient feedback governing AGN-galaxy co-evolution. The WISSH project aims at investigating the multi-wavelength properties of 85 WISE/SDSS selected type 1 (i.e. unobscured) HyLQSOs at the cosmic noon, to study their spectral and wind properties. We focuse on the X-ray emission of this sample, processing Chandra/XMM-Newton data. The slope of the primary power-law (Γ) and possible intrinsic column density (N_H ) are measured. Γ is broadly consistent with the expected range ~1.8-2. About 24% of the sources for which N_H can be estimated exhibits N_H≥10^22 cm^(-2). The observed quasars have an intrinsic 2-10 keV luminosity L_X≈10^(43-46) erg/s. Knowing the bolometric and monochromatic 2500 Å (L_2500 ) luminosities, we derive the bolometric correction (k_bol ) and X-ray - to - optical index (α_OX ). In the L_bol-k_bol and L_2500-α_OX, WISSH QSOs arrange anomalously with respect to literature relations, i.e. covering a wide range of k_bol and α_OX for a given bolometric or monochromatic luminosity. This evidence highlights a possible different coupling in the accretion disk - corona. The offset of the observed α_OX from the expected one (from literature relations) defines ∆(α_OX). Having ∆(α_OX )<-0.2, ~22% of WISSH sources are “X-ray weak”, i.e. characterised by a lower relative contribution of the X-ray emission to L_bol compared to lower-luminous samples. From M_BH, Eddington ratio is evaluated as λ_Edd≈0.1-3. Previously found correlations with Γ do not seem to work at λ_Edd ~ 1, where data are highly dispersed. In the λ_Edd-N_H plane, WISSH blue quasars occupy the “forbidden region” (i.e. high-λ_Edd/high-N_H), identified by Fabian+08 and typically associated with red sources (E(B-V)>0.15).

Abstract
Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Degli Agosti, Cecilia
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Ordinamento Cds
DM270
Parole chiave
hyper-luminous quasars cosmic noonX-ray emission Chandra/XMM-Newton WISSH project feedback
Data di discussione della Tesi
29 Settembre 2023
URI

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