2007PASJ...59..717A

begin{HTML}We present spectroscopy results of Lyman break galaxies (LBGs) at <I>z</I≳5 in the J0053+1234 field. Among five bright candidates with <I>z'</I><25.0mag, two objects are confirmed to be at <I>z</I≳5. The equivalent widths (EWs) of Lyα emission of the 2 LBGs are not so strong as to be detected as Lyα emitters, and one of them shows strong low-ionization interstellar (LIS) metal absorption lines. Two faint objects with <I>z'</I>>=25.0 mag are also confirmed to be at <I>z</I≳5, and their spectra show strong Lyα emission in contrast to bright ones. These results suggest a deficiency of strong Lyα emission in bright LBGs at <I>z</I> ∼ 5, as discussed in our previous paper. Combined with our previous spectra of LBGs at <I>z</I>&sim 5, obtained around the Hubble Deep Field-North (HDF-N), we made a composite spectrum of luminous (M_{1400} <=21.5mag) LBGs at <I>z</I≳5. The resultant spectrum shows weak Ly α emission and strong LIS absorptions, which suggest that the bright LBGs at <I>z</I≳5 have chemically evolved at least to ∼0.1 solar metallicity. For a part of our sample in the HDF-N region, we obtained near-to-mid infrared data, which constrain the stellar masses of these objects. With the stellar mass and the metallicity estimated from the LIS absorptions, the metallicities of the LBGs at <I>z</I≳5 tend to be lower than those of galaxies with the same stellar mass at <I>z</I> \lesssim 2, although the uncertainty is very large.