Quasar Standardization: Overcoming Selection Biases and Redshift Evolution

Quasars (QSOs) are extremely luminous active galactic nuclei currently observed up to redshift z = 7.642. As such, they have the potential to be the next rung of the cosmic distance ladder beyond Type Ia supernovae, if they can reliably be used as cosmological probes. The main issue in adopting QSOs...

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Bibliographic Details
Published in:The Astrophysical journal 2022-06, Vol.931 (2), p.106
Main Authors: Dainotti, Maria Giovanna, Bargiacchi, Giada, Lenart, Aleksander Łukasz, Capozziello, Salvatore, Ó Colgáin, Eoin, Solomon, Rance, Stojkovic, Dejan, Sheikh-Jabbari, M. M.
Format: Article
Language:English
Subjects:
Active galactic nuclei
Astrophysics
Correlation
Evolution
Gamma ray bursts
Gamma rays
Hubble diagram
Quasars
Red shift
Reliability
Standardization
Statistical methods
Statistical tests
Supernovae
X-ray fluxes
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Summary:Quasars (QSOs) are extremely luminous active galactic nuclei currently observed up to redshift z = 7.642. As such, they have the potential to be the next rung of the cosmic distance ladder beyond Type Ia supernovae, if they can reliably be used as cosmological probes. The main issue in adopting QSOs as standard candles (similarly to gamma-ray bursts) is the large intrinsic scatter in the relations between their observed properties. This could be overcome by finding correlations among their observables that are intrinsic to the physics of QSOs and not artifacts of selection biases and/or redshift evolution. The reliability of these correlations should be verified through well-established statistical tests. The correlation between the ultraviolet and X-ray fluxes developed by Risaliti & Lusso is one of the most promising relations. We apply a statistical method to correct this relation for redshift evolution and selection biases. Remarkably, we recover the the same parameters of the slope and the normalization as Risaliti & Lusso. Our results establish the reliability of this relation, which is intrinsic to the QSO properties and not merely an effect of selection biases or redshift evolution. Hence, the possibility to standardize QSOs as cosmological candles, thereby extending the Hubble diagram up to z = 7.54.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac6593