A Deep Chandra View of the NGC 404 Central Engine
  We present the results of a 100 ks {\it Chandra} observation of the NGC 404
nuclear region. The long exposure and excellent spatial resolution of {\it
Chandra} has enabled us to critically examine the nuclear environment of NGC
404, which is known to host a nuclear star cluster and potentially an
intermediate-mass black hole (on the order of a few times $10^5$ \Msun). We
find two distinct X-ray sources: a hard, central point source coincident with
the optical and radio centers of the galaxy, and a soft extended region that is
coincident with areas of high H$\alpha$ emission and likely recent star
formation. When we fit the 0.3-8 keV spectra of each region separately, we find
the hard nuclear point source to be dominated by a power law (\PL = 1.88),
while the soft off-nuclear region is best fit by a thermal plasma model ($kT$ =
0.67 keV). We therefore find evidence for both a power law component and hot
gas in the nuclear region of NGC 404. We estimate the 2-10 keV luminosity to be
1.3$^{+0.8}_{-0.5}\times10^{37}$ erg s$^{-1}$. A low-level of diffuse X-ray
emission is detected out to $\sim$15\as ($\sim$0.2 kpc) from the nucleus. We
compare our results to the observed relationships between power law photon
index and Eddington ratio for both X-ray binaries and low luminosity active
galaxies and find NGC 404 to be consistent with other low luminosity active
galaxies. We therefore favor the conclusion that NGC 404 harbors an
intermediate-mass black hole accreting at a very low level.
