Probing the hot X-ray gas in the narrow-line region of Mrk 3
  We study the prototypical Seyfert 2 galaxy, Markarian 3, based on imaging and
high-resolution spectroscopy observations taken by the Chandra X-ray
Observatory. We construct a deconvolved X-ray image, which reveals the S-shaped
morphology of the hot gas in the narrow line region (NLR). While this
morphology is similar to the radio and [O III] emission, the distribution of
the X-ray gas is broader than that obtained at these other wavelengths. By
mapping the density and temperature distribution of the hot gas in the NLR, we
demonstrate the presence of shocks towards the west ($M=2.5^{+1.0}_{-0.6}$) and
east ($M=1.5^{+1.0}_{-0.5}$). Moreover, we compute the flux ratios between the
[O III] and $0.5-2$ keV band X-ray luminosity and show that it is non-uniform
in the NLR with the western side of the NLR being more highly ionized. In
addition, based on the Chandra grating data we investigate the line ratios of
the Si XIII triplet, which are not consistent with pure photoionization. Based
on these results, we suggest that in the NLR of Mrk 3 both photoionization and
collisional ionization act as excitation mechanisms. We conclude that the
canonical picture, in which photoionization is solely responsible for exciting
the interstellar medium in the NLR of Seyfert galaxies, may be overly
simplistic. Given that weak and small-scale radio jets are commonly detected in
Seyfert galaxies, it is possible that shock heating plays a non-negligible role
in the NLR of these galaxies.
