Testing Physical and Phenomenological Models to Explain the Origin of the Soft Excess in Type-1 AGN

Abstract Active galactic nuclei (AGN) exhibit an excess of X-ray emission below ∼1 keV compared to the 2–10 keV continuum extrapolation. This feature is commonly named soft excess, and its origin is currently debated for type-1 AGN. To investigate the nature of the soft excess, we perform a systematic analysis of XMM-Newton and NuSTAR simultaneous observations for a sample of 22 type-1 AGN. For this, we consider a baseline model composed of the intrinsic continuum, the reflection component, and the soft excess. We test different soft excess scenarios by fitting models of Comptonization, relativistically blurred reflection, ionized partial-covered absorption, and black-body emission. The final best fit requires multiple components for the soft excess, with a 1%–10% contribution of the relativistically blurred reflection at the accretion disk and 10%–80% of the black body component. We find that 88% of the spectra in the sample require the contribution of disk reflection and 92% require black body, where the luminosities of both components correlate. Ionized partial-covered absorption (warm absorber) is also observed in 84% of the objects. We also find that the black-body luminosity correlates with the accretion rate of the source. Using the temperature of the black body and its luminosity, we derive the expected radius at which this black body emission originates, which shows values consistent with originating at the inner part of the accretion disk.