Lyman Break Galaxies at z∼5: Rest-Frame UV Spectra. II
Abstract
We present spectroscopy results of Lyman break galaxies (LBGs) at z∼5 in the J0053+1234 field. Among five bright candidates with z'<25.0mag, two objects are confirmed to be at z∼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 z'geq25.0 mag are also confirmed to be at z∼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 z ∼ 5, as discussed in our previous paper. Combined with our previous spectra of LBGs at z∼5, obtained around the Hubble Deep Field-North (HDF-N), we made a composite spectrum of luminous (M_{1400} leq 21.5mag) LBGs at z∼5. The resultant spectrum shows weak Ly α emission and strong LIS absorptions, which suggest that the bright LBGs at z∼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 z∼5 tend to be lower than those of galaxies with the same stellar mass at z lesssim 2, although the uncertainty is very large.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- August 2007
- DOI:
- 10.1093/pasj/59.4.717
- arXiv:
- arXiv:0705.1145
- Bibcode:
- 2007PASJ...59..717A
- Keywords:
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- galaxies: evolution;
- galaxies: formation;
- galaxies: high-redshift;
- Astrophysics
- E-Print:
- 17 pages, 5 figures, accepted for publication in PASJ