Séminaire/Seminar Galaxies |
| « AGN populations: an X-ray to mid-infrared perspective » |
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Brivael Laloux |
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Active galactic nuclei (AGN) are best understood through a multi-wavelength approach, as their observed properties and detectability strongly depend on both the physical processes powering their emission and the effects of obscuration. In this talk, I will present a brief overview of my work on AGN populations, from an X-ray perspective during my PhD to recent investigations using the unique near-infrared capabilities of Euclid.
I will first discuss how X-ray observations provide a powerful probe on AGN obscuration and intrinsic accretion. Using X-ray-selected AGN samples, I investigated the demographics of obscured AGN, with particular emphasis on the fraction of Compton-thick sources and its dependence on AGN properties. I will also present evidence for differences in accretion rates between obscured and unobscured populations, providing insights into the connection between obscuration and black-hole growth. I will then turn to my recent work using the Euclid Quick Data Release (Q1). Robustly disentangling AGN and host-galaxy emission is essential for constraining their physical properties and studying their co-evolution. Leveraging Euclid's NIR data, I perform spectral energy distribution fitting to simultaneously characterise AGN and their host galaxies, and use realistic simulated SEDs to assess and improve the reliability of the derived measurements. I will show how AGN emission affects the estimation of galaxy properties and how SED fitting can be used as a diagnostic for AGN identification. Comparing AGN selected through different techniques further reveals that individual methods probe partially distinct populations, underlining the importance of multi-wavelength approaches in mitigating selection biases. Finally, I will present preliminary results on the synergies between eROSITA and Euclid DR1, highlighting their potential to construct large and homogeneous AGN samples for studies of black-hole and galaxy co-evolution across cosmic time. |
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jeudi 27 août 2026 - 11:30 Salle Entresol Daniel Chalonge Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |