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arXiv · 1007.2847

Spectroscopy of z~5 Lyman Break Galaxies in the ESO Remote Galaxy Survey

L. S. Douglas·M. N. Bremer·M. D. Lehnert·E. R. Stanway·Bo Milvang-Jensen
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Abstract

(ABRIDGED) We present the global results of a large spectroscopic survey carried out in order to identify z~ 5 Lyman break galaxies (LBGs) across ten widely-separated fields to I_{AB}=26.3. The redshifts of seventy 4.6<z<5.6 LBGs were identified. We find no significant difference in the frequency of high equivalent-width line emitters between z~3 and our z~5 samples. The rest-frame UV continuum slope of a typical z~5 line-emitting galaxy is bluer than that of a typical break-only galaxy, a difference that is difficult to explain purely by differences in the ages of their stellar populations. Variation in metallicity and/or dust extinction can more straightforwardly account for this difference. Given their UV-continuum slopes, the typical z~5 LBGs have metallicities a factor of three lower than those of LBGs at z~3. HST imaging indicates that a large majority of the spectroscopically-confirmed LBGs in our sample are members of multiple systems and/or show disturbed morphology. Using local LBG analogues as a model, this multiplicity could be explained either by super-starburst regions within a larger unseen structure, or by a high incidence of merging events at this epoch. The current data cannot distinguish between these two possibilities. The surface density of z~5 LBGs in two fields is considerably higher than in the rest. Both show clear spikes in their redshift distributions indicating strong three-dimensional clustering. Neither structure can be bound given their depth in redshift and probably extend beyond the observed fields. The three-dimensional distances between LBGs in the structures are too large for them to have triggered their starbursts through mutual gravitational interaction, and so it is likely that the short-lived LBGs represent only a small fraction of the baryons in the structures.

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L. S. Douglas, M. N. Bremer, M. D. Lehnert, E. R. Stanway, Bo Milvang-Jensen. 2010-07-16. Spectroscopy of z~5 Lyman Break Galaxies in the ESO Remote Galaxy Survey. https://doi.org/10.1111/j.1365-2966.2010.17375.x

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