  Combining a theoretical model of mass accretion onto a galactic center with a
high-resolution $N$-body/SPH simulation, we investigate the formation of an
intermediate massive black hole (IMBH) during the hierarchical formation of a
small spiral galaxy (with a total mass of $10^{10}M_{\odot}$) in the high-$z$
universe. We found that the rate of average mass accretion to the nucleus due
to the radiation drag exerted by newly formed stars in the forming galaxy is
$\approx 10^{-5}M_{\odot}$yr$^{-1}$. As a result of this accretion, an IMBH
with $\approx 10^{4}M_{\odot}$ can be formed in the center of the spiral galaxy
at $z\sim 4$. We found that a central BH coevolves with the dark matter halo
from $z\sim 15$ to $z\sim 2$. The mass ratio of the BH to the dark matter halo
is nearly constant $\approx (1-3) \times 10^{-6}$ from $z\sim 10$ to $z\sim 2$.
This is because that change in the dark matter potential enhances star
formation in the central part of the galaxy, and as a result the BH evolves due
to mass accretion via the radiation drag. Therefore, our model naturally
predicts a correlation between massive BHs and dark matter halos. Moreover, it
is found that the final BH-to-bulge mass ratio ($\approx 5\times 10^{-5}$) in a
small spiral galaxy at high-$z$ is much smaller than that in the large galaxies
($\approx 10^{-3}$). Our results also suggest that the scatter in the observed
scaling relations between the bulge mass and black hole mass are caused by a
time lag between BH growth and growth of bulge. We also predict that the X-ray
luminosity of AGN is positively correlated with the CO luminosity in the
central region. By comparing our results with the properties of Lyman break
galaxies (LBGs), it is predicted that some LBGs have massive BHs of $\approx
10^{6}-10^{7}M_{\odot}$.
