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Deep Spectroscopic Survey of Lyman Break Galaxies at z~5

M. Ando·K. Ohta·I. Iwata·M. Akiyama·K. Aoki·N. Tamura
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Abstract

We report results of deep optical spectroscopy with Subaru/FOCAS for Lyman Break Galaxy (LBG) candidates at z~5. So far, we made spectroscopic observations for 24 LBG candidates among ~200 bright (z'<25.0) LBG sample and confirmed 9 objects to be LBGs at z~5. Intriguingly, these bright LBGs show no or a weak Ly-alpha emission and relatively strong low ionization interstellar metal absorption lines. We also identified 2 faint (z'>25.0) objects to be at z~5 with their strong (EW_rest>20AA) Ly-alpha emission. Combining our results with other spectroscopic observations of galaxies at the similar redshift range, we found a clear luminosity dependence of EW_rest of Ly-alpha emission, i.e., the lack of strong Ly-alpha emission in bright LBGs. If the absence of Ly-alpha emission is due to dust absorption, these results suggest that bright LBGs at z~5 are in dusty and more chemically evolved environment than faint ones. This interpretation implies that bright LBGs started star formation earlier than faint ones, suggesting biased star formation.

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M. Ando, K. Ohta, I. Iwata, M. Akiyama, K. Aoki, N. Tamura. 2005-10-30. Deep Spectroscopic Survey of Lyman Break Galaxies at z~5. https://arxiv.org/abs/astro-ph/0510830

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