Lyman Break Galaxies at z~5: Rest-Frame UV Spectra. III
  We present results of optical spectroscopic observations of candidates of
Lyman Break Galaxies (LBGs) at $z \sim 5$ in the region including the GOODS-N
and the J0053+1234 region by using GMOS-N and GMOS-S, respectively. Among 25
candidates, five objects are identified to be at $z \sim 5$ (two of them were
already identified by an earlier study) and one object very close to the
color-selection window turned out to be a foreground galaxy. With this
spectroscopically identified sample and those from previous studies, we derived
the lower limits on the number density of bright ($M_{UV}<-22.0$ mag) LBGs at
$z \sim 5$. These lower limits are comparable to or slightly smaller than the
number densities of UV luminosity functions (UVLFs) that show the smaller
number density among $z \sim 5$ UVLFs in literature. However, by considering
that there remain many LBG candidates without spectroscopic observations, the
number density of bright LBGs is expected to increase by a factor of two or
more. The evidence for the deficiency of UV luminous LBGs with large Ly$\alpha$
equivalent widths was reinforced. We discuss possible causes for the deficiency
and prefer the interpretation of dust absorption.
