[phys4phys] Seminar Katedre za astronomiju - 10. februar 2026.

[Katedra za astronomiju]

                      Seminar iz astronomije i astrofizike

                                Anastasia Shlentsova
   (Pontificia Universidad Católica de Chile, Čile; Università degli Studi di Firenze,
             INAF - Osservatorio Astrofisico di Arcetri, Italija)

              "Lighting up a new standard candle: calibration of AGNs"

           utorak, 10. februar 2026. godine, u 18 sati, u ucionici 809.


Abstract:
Exploring new/alternative standard candles is crucial for advancing 
cosmology. One spanning a wide redshift range, like quasars (QSOs), can 
provide orthogonal constraints on model parameters, among which H0, with 
its current tension, is particularly relevant. The 2 keV to 2500 Å flux 
ratio in QSOs shows great potential as a cosmological tool (e.g., 
Lusso+20, Sacchi+22) if suitable subsets are identified, akin to the 
corrections applied to supernovae. We investigate various properties of 
QSOs to deepen our understanding of QSO physics and refine the selection 
criteria for a new cosmological quasar sample.
We specifically examine the most luminous QSOs exhibiting strong outflows 
in the C IV emission line to clarify the relation between the strength of 
the outflows and X-ray emission, thereby enhancing our understanding of 
the mechanisms within active galactic nuclei (AGN) engines. Using targeted 
observations with Chandra, we determine the slope of the 2 keV to 2500 Å 
luminosity relation and explore how the C IV blueshift correlates with the 
steepness of the UV-to-X-ray spectral energy distribution. To gain 
insights into the fundamental processes underlying the 2 keV to 2500 Å 
luminosity relation, we analyse the slopes of the relation measured using 
multi-epoch XMM observations of specific sources. Finally, to investigate 
the correlations between the dispersion of the 2 keV to 2500 Å luminosity 
relation, fundamental AGN properties, and optical variability, we assess 
several variability features from the ZTF optical light curves and conduct 
a dimension reduction analysis.

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       DEPARTMENT OF ASTRONOMY
       Faculty of Mathematics
       University of Belgrade

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