X-CIGALE: fitting AGN/galaxy SEDs from X-ray to infrared
  CIGALE is a powerful multiwavelength spectral energy distribution (SED)
fitting code for extragalactic studies. However, the current version of CIGALE
is not able to fit X-ray data, which often provide unique insights into AGN
intrinsic power. We develop a new X-ray module for CIGALE, allowing it to fit
SEDs from the X-ray to infrared (IR). We also improve the AGN fitting of CIGALE
from UV-to-IR wavelengths. We implement a modern clumpy two-phase torus model,
SKIRTOR. To account for moderately extincted type 1 AGNs, we implement
polar-dust extinction. We publicly release the source code (named X-CIGALE). We
test X-CIGALE with X-ray detected AGNs in SDSS, COSMOS, and AKARI-NEP. The
fitting quality (as indicated by reduced $\chi^2$) is good in general,
indicating that X-CIGALE is capable of modelling the observed SED from X-ray to
IR. We discuss constrainability and degeneracy of model parameters in the
fitting of AKARI-NEP, for which excellent mid-IR photometric coverage is
available. We also test fitting a sample of AKARI-NEP galaxies for which only
X-ray upper limits are available from Chandra observations, and find that the
upper limit can effectively constrain the AGN SED contribution for some
systems. Finally, using X-CIGALE, we assess the ability of Athena to constrain
the AGN activity in future extragalactic studies.
