GOLDRUSH. IV. Luminosity Functions and Clustering Revealed with
  ~4,000,000 Galaxies at z~2-7: Galaxy-AGN Transition, Star Formation
  Efficiency, and Implication for Evolution at z>10
  We present new measurements of rest-UV luminosity functions and angular
correlation functions from 4,100,221 galaxies at z~2-7 identified in the
Subaru/Hyper Suprime-Cam survey and CFHT Large-Area U-band Survey. The obtained
luminosity functions at z~4-7 cover a very wide UV luminosity range of
~0.002-2000L*uv combined with previous studies, revealing that the dropout
luminosity function is a superposition of the AGN luminosity function dominant
at Muv<-24 mag and the galaxy luminosity function dominant at Muv>-22 mag,
consistent with galaxy fractions based on 1037 spectroscopically-identified
sources. Galaxy luminosity functions estimated from the spectroscopic galaxy
fractions show the bright end excess beyond the Schechter function at >2sigma
levels, which is possibly made by inefficient mass quenching, low dust
obscuration, and/or hidden AGN activity. By analyzing the correlation functions
at z~2-6 with halo occupation distribution models, we find a weak redshift
evolution (within 0.3 dex) of the ratio of the star formation rate (SFR) to the
dark matter accretion rate, SFR/(dMh/dt), indicating the almost constant star
formation efficiency at z~2-6, as suggested by our earlier work at z~4-7.
Meanwhile, the ratio gradually increases with decreasing redshift at z<5 within
0.3 dex, which quantitatively reproduces the redshift evolution of the cosmic
SFR density, suggesting that the evolution is primarily driven by the increase
of the halo number density due to the structure formation, and the decrease of
the accretion rate due to the cosmic expansion. Extrapolating this calculation
to higher redshifts assuming the constant efficiency suggests a rapid decrease
of the SFR density at z>10 with $\propto10^{-0.5(1+z)}$, which will be directly
tested with JWST.
