  We present a simple scenario where the formation of galactic bulges was
regulated by the dark halo gravity and regulated the growth of the central
supermassive black hole. Assuming the angular momentum is low, we suggest that
bulges form in a runaway collapse due to the "gravothermal" instability once
the central gas density or pressure exceeds certain threshold (Xu & Zhao 2007).
We emphasize that the threshold is nearly universal, set by the background NFW
dark matter gravity $g_{DM} \sim 1.2 \times 10^{-8}{\rm cm} {\rm sec}^{-2}$ in
the central cusps of halos. Unlike known thresholds for gradual formation of
galaxy disks, we show that the universal "halo-regulated" star formation
threshold for spheroids matches the very high star formation rate and star
formation efficiency shown in high-redshift observations of central starburst
regions. The starburst feedback also builds up a pressure shortly after the
collapse. This large pressure could both act outward to halt further infall of
gas from larger scale, and act inward to counter the Compton-thick wind
launched from the central black hole in an Eddington accretion. Assuming the
feedback balancing inward and outward forces, our scenario naturally gives rise
to the black hole-bulge relationships observed in the local universe.
