The Faint End of the Quasar Luminosity Function at $z \sim 5$ from the
  Subaru Hyper Suprime-Cam Survey
  We present the quasar luminosity function at $z \sim 5$ derived from the
optical wide-field survey data obtained as a part of the Subaru strategic
program (SSP) with Hyper Suprime-Cam (HSC). From $\sim$81.8 deg$^2$ area in the
Wide layer of the HSC-SSP survey, we selected 224 candidates of low-luminosity
quasars at $z \sim 5$ by adopting the Lyman-break method down to $i = 24.1$
mag. Based on our candidates and spectroscopically-confirmed quasars from the
Sloan Digital Sky Survey (SDSS), we derived the quasar luminosity function at
$z \sim 5$ covering a wide luminosity range of $-28.76 < M_{\rm 1450} < -22.32$
mag. We found that the quasar luminosity function is fitted by a double
power-law model with a break magnitude of $M^{*}_{1450} =
-25.05^{+0.10}_{-0.24}$ mag. The inferred number density of low-luminosity
quasars is lower, and the derived faint-end slope, $-1.22^{+0.03}_{-0.10}$, is
flatter than those of previous studies at $z \sim 5$. A compilation of the
quasar luminosity function at $4 \leq z \leq 6$ from the HSC-SSP suggests that
there is little redshift evolution in the break magnitude and in the faint-end
slope within this redshift range, although previous studies suggest that the
faint-end slope becomes steeper at higher redshifts. The number density of
low-luminosity quasars decreases more rapidly from $z \sim 5$ to $z \sim 6$
than from $z \sim 4$ to $z \sim 5$.
