Disentangling AGN and Star Formation in Soft X-rays. (arXiv:1208.6233v1 [astro-ph.CO])

Disentangling AGN and Star Formation in Soft X-rays. (arXiv:1208.6233v1 [astro-ph.CO]):
We have explored the interplay of star formation and AGN activity in soft
X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a
combination of low resolution CCD spectra from Chandra and XMM-Newton, we
modeled the soft emission of 34 Sy2s using power law and thermal models. For
the 11 sources with high signal-to-noise Chandra imaging of the diffuse host
galaxy emission, we estimate the luminosity due to star formation by removing
the AGN, fitting the residual emission. The AGN and star formation
contributions to the soft X-ray luminosity (i.e. L$_{x,AGN}$ and L$_{x,SF}$)
for the remaining 24 Sy2s were estimated from the power law and thermal
luminosities derived from spectral fitting. These luminosities were scaled
based on a template derived from XSINGS analysis of normal star forming
galaxies. To account for errors in the luminosities derived from spectral
fitting and the spread in the scaling factor, we estimated L$_{x,AGN}$ and
L$_{x,SF}$ from Monte Carlo simulations. These simulated luminosities agree
with L$_{x,AGN}$ and L$_{x,SF}$ derived from Chandra imaging analysis within a
3\sigma\ confidence level. Using the infrared [NeII]12.8\mu m and [OIV]26\mu m
lines as a proxy of star formation and AGN activity, respectively, we
independently disentangle the contributions of these two processes to the total
soft X-ray emission. This decomposition generally agrees with L$_{x,SF}$ and
L$_{x,AGN}$ at the 3\sigma\ level. In the absence of resolvable nuclear
emission, our decomposition method provides a reasonable estimate of emission
due to star formation in galaxies hosting type 2 AGN.