Abstract

Contributed Talk - Splinter SMBHs

Thursday, 10 September 2026, 17:09   (MW-0250)

The impact of AGN emission on SED-derived physical properties with Euclid

Brivael Laloux
INAF - Capodimonte

Understanding the co-evolution of active galactic nuclei (AGN) and their host galaxies requires the robust decomposition of their respective emission to reliable constrain the AGN and host galaxy physical properties. Leveraging the unique NIR capabilities of Euclid’s Quick Data Release (Q1), I performed spectral energy distribution (SED) fitting to simultaneously constrain the properties of AGN and their hosts. Moreover, I present a new method to assess and improve the reliability of the measurements, based on simulated SEDs built from combined quasar and galaxy observations. I quantify how AGN emission impacts physical property estimations and demonstrate that SED fitting serves as a powerful diagnostic for AGN identification, achieving 85% purity and completeness. Furthermore, a comparative analysis of AGN selected via different methods reveals that these techniques probe partially distinct populations, highlighting the importance of multi-wavelength, multi-method approaches to mitigate selection biases in studies of galaxy evolution. Finally, we investigate the X-ray to mid-infrared luminosity relation and the evolution of the stellar mass–bolometric luminosity correlation across cosmic time. These results validate the utility of Euclid for constructing large, homogeneous AGN samples, providing a crucial foundation for mapping the co-evolution of supermassive black holes and their hosts over a wide range of redshifts. I will conclude my talk by showcasing how the community can leverage this catalogue for future AGN studies.