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Open AccessArticle

Quasars: From the Physics of Line Formation to Cosmology

National Institute for Astrophysics (INAF), Astronomical Observatory of Padova, IT-35122 Padova, Italy
Astronomical Observatory, 11060 Belgrade, Serbia
Instituto de Astrofisíca de Andalucía, IAA-CSIC, Glorieta de la Astronomia s/n, E-18008 Granada, Spain
Dipartimento di Fisica & Astronomia “Galileo Galilei”, Università di Padova, IT-35122 Padova, Italy
Instituto de Astronomía, UNAM, Mexico D.F. 04510, Mexico
INAF, Osservatorio di Astrofisica e Scienza dello Spazio, IT-40129 Bologna, Italy
Author to whom correspondence should be addressed.
Atoms 2019, 7(1), 18;
Received: 26 November 2018 / Revised: 28 January 2019 / Accepted: 28 January 2019 / Published: 4 February 2019
(This article belongs to the Special Issue SPIG2018)
Quasars accreting matter at very high rates (known as extreme Population A (xA) or super-Eddington accreting massive black holes) provide a new class of distance indicators covering cosmic epochs from the present-day Universe up to less than 1 Gyr from the Big Bang. The very high accretion rate makes it possible that massive black holes hosted in xA quasars can radiate at a stable, extreme luminosity-to-mass ratio. This in turn translates into stable physical and dynamical conditions of the mildly ionized gas in the quasar low-ionization line emitting region. In this contribution, we analyze the main optical and UV spectral properties of extreme Population A quasars that make them easily identifiable in large spectroscopic surveys at low- ( z 1 ) and intermediate-z (2 z 2.6), and the physical conditions that are derived for the formation of their emission lines. Ultimately, the analysis supports the possibility of identifying a virial broadening estimator from low-ionization line widths, and the conceptual validity of the redshift-independent luminosity estimates based on virial broadening for a known luminosity-to-mass ratio. View Full-Text
Keywords: black hole physics; cosmology; quasar spectroscopy; cosmological parameters; ionized gas; broad line region black hole physics; cosmology; quasar spectroscopy; cosmological parameters; ionized gas; broad line region
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Marziani, P.; Bon, E.; Bon, N.; del Olmo, A.; Martínez-Aldama, M.L.; D’Onofrio, M.; Dultzin, D.; Negrete, C.A.; Stirpe, G.M. Quasars: From the Physics of Line Formation to Cosmology. Atoms 2019, 7, 18.

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