SPACE seminar: Micol Benetti - "Quasar Cosmology and tensions with cosmological probes" —CANCELLED—

Tuesday 26 May 2026, 12:00 → 13:00 Europe/Rome

Aula 4 (San Marcellino)

Speaker:  Prof. Micol Benetti (SSM)

Title: Quasar Cosmology and tensions with cosmological probes

Abstract: 

In recent years, the possibility of employing quasars as standard candles through the UV–X-ray luminosity relation has been the subject of significant debate. These probes offer the potential to extend the Hubble diagram up to z ∼ 7, thereby accessing high-redshift regimes that remain largely unexplored by conventional methods.

In this contribution, I present constraints on cosmological models within the ΛCDM framework, as well as on extended dark energy scenarios, based on the Lusso & Risaliti catalog. The analysis assesses the consistency of quasar-based measurements with other key cosmological probes, including Type Ia Supernovae (SNe Ia), Baryon Acoustic Oscillations (BAO), DES, and the Cosmic Microwave Background (CMB).

The results indicate that minimal extensions of the standard cosmological model are insufficient to alleviate current tensions, whereas interacting dark sector models exhibit improved concordance across datasets. These findings underscore the potential of quasars as a complementary probe for bridging the gap between late- and early-Universe observations.

References: 

1. G. Bargiacchi, M. Benetti, S. Capozziello, E. Lusso, G. Risaliti and M. Signorini, "Quasar cosmology: dark energy evolution and spatial curvature", Mon. Not. Roy. Astron. Soc. 515, no.2, 1795-1806 (2022) [arXiv:2111.02420 [astro-ph.CO]].
2. M. Benetti, G. Bargiacchi, G. Risaliti, S. Capozziello, E. Lusso and M. Signorini, "Quasar cosmology II: Joint analyses with cosmic microwave background", Phys. Dark Univ. 49, 101983 (2025) [arXiv:2506.21477 [astro-ph.CO]].
3. E. Lusso, G. Risaliti, E. Nardini, G. Bargiacchi, M. Benetti, S. Bisogni, S. Capozziello, F. Civano, L. Eggleston and M. Elvis, et al., "Quasars as standard candles III. Validation of a new sample for cosmological studies", Astron. Astrophys. 642, A150 (2020) [arXiv:2008.08586 [astro-ph.GA]]

 

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