ned the SINGS high resolution spectra and find that averaged over a 365 arcsec$^2$ region around the nucleus of M51, the \[O IV\] line flux is 2.7 times higher than the \[Fe II\] flux.[^4] In the high resolution data cubes of the nuclear region, the \[O IV\] line flux dominates the \[O IV\] + \[Fe II\] blend and the \[O IV\] emission distribution derived from the low resolution spectra accurately reflects the distribution seen in the high resolution spectra. In Figure \[figure-15\], we compare the \[O IV\] surface brightness to the warm ($left$) and hot ($right$) H$_2$ distributions. The \[O IV\] emission is brightest in the nuclear region at 1.2 $\times$ $\mathrm{10^{-17}}$ W $\mathrm{m^{-2}}$ and within a 0.5 kpc radius of the nucleus, the peak is coincident with the peak in the mass of the hot H$_2$. \[O IV\] surface brightness decreases from the nucleus to the inner spiral arm by 50 %. We resolve weaker \[O IV\] emission within the warm and hot H$_2$ spiral arms. The \[O IV\] surface brightness is a factor of $\sim$ 6 lower in the spiral arms than the peak intensity found in the nucleus. The \[O IV\] emission within the nuclear region of M51 is likely due to the weak Seyfert 2 nucleus [@ford85] and is possibly associated with shocked gas from the outflows of the AGN. The peak of the \[O IV\] emission coincides with the nuclear peak in hot H$_2$ mass, indicating that the hot H$_2$ phase in the nuclear region of the galaxy is AGN or shock heated. In the nuclear region we observe a factor of 12 times greater warm H$_2$ mass than the hot H$_2$ mass. The warm H$_2$ mass is much greater within the spiral arms than within the nucleus and the warm-to-hot mass ratio is lowest in the nuclear region where the \[O IV\] flux is greatest. In general, nuclear activity and shocks heat the ISM more efficiently causing the higher surface density of hot H$_2$.

X-ray studies of M51 have revealed bright X-ray emission from the nucleus, the extranuclear cloud (XNC, to the south of the nucleus), and the northern loop [@wil01; @mad