Research: Modeling the Spectral Energy Distribution of AGN


Examples of template fits to the observed Spectral Energy Distribution of extragalactic sources using the CIGALE code. Blue points are the flux densities of galaxies, the red lines are the templates (AGN + stars) that best fit the photometric data. The orange (dotted) lines show the AGN template. The left and right panels show galaxies with different contribution of AGN emission, 20 and 60% of the total infrared luminosity, respectively. More details in Ciesla et al. (2015)

Template fits to the multiwavelength (UV to far-IR) Spectral Energy Distribution (SED) of galaxies is a powerful approach to study the physical mechanism dominating the integrated emission of extragalactic sources, e.g. stars vs AGN, and to infer physical parameters for the stellar population (e.g. mass, star-formation history) or the AGN (e.g. integrated accretion luminosity).

CIGALE is a fast state-of-the-art Bayesian galaxy SED fitting code that reconstructs SEDs by using a stellar population library, a star-formation history parametric model and the energy balance principle, i.e., the energy absorbed by dust in UV-optical is reemitted in the IR.

We have contributed to the inclusion of AGN templates in the CIGALE to be able to infer properties such as stellar mass an star-formation rate of the underlying host galaxy for large samples of AGN detected in current multiwavelength surveys. The performance of the code has been tested on mock data and the results are presented in Ciesla et al. (2015). Work is in progress to apply this code to real AGN detected in X-ray survey observations.