Euclid Q1: AGN and host galaxy physical properties

Measuring the physical properties of AGN and their host galaxies is key to understand their parallel evolution, particularly the correlation between stellar mass and black hole mass. However, hosting a bright AGN can dilute the host galaxy’s emission and bias the spectral energy distribution (SED) fitting measurements, potentially overestimating the host galaxy’s stellar mass. Euclid’s unique photometric capabilities provide near-infrared photometry, crucial for separating AGN and host galaxy contributions, thus improving our physical parameter measurements, for an unprecedentedly large sample of AGN candidates. I will present the AGN and host galaxy physical parameter catalogue for the three Euclid Q1 deep fields: North, South and Fornax. We developped a method to assess the reliability of the SED fitting measurements, leading to a more robust catalogue for the users. Using these measurements, I identify true AGN and compare this new selection with X-ray, optical, NIR and MIR color-color approaches. From the physical property differences, I demonstrate that these selection methods probe different AGN populations, and their combination provides a more comprehensive picture of AGN. I will present the AGN space density and specific accretion rate distribution across redshift, AGN luminosity and stellar masses, which will be extended to Euclid DR1 (∼300x wider). I will discuss the implications of my results and the role of Euclid to understand AGN and host galaxy co-evolution.