The Gemini Deep Deep Survey: II. Metals in the Star-Forming Galaxies at Redshift 1.3<z<2

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  • 15 October 2003
Abstract
The goal of the Gemini Deep Deep Survey (GDDS) is to study an unbiased sample of K1.3. The selected objects have colors typical of irregular and Sbc galaxies. Strong [OII] emission indicates high star formation activity in the HII regions (SFR \~13-106 M_sun/yr). The high S/N composite spectrum shows strong ISM MgII and FeII absorption, together with weak MnII and MgI lines. The FeII column density, derived using the curve of growth analysis, is logN_FeII = 15.54^{+0.23}_{-0.13}. This is considerably larger than typical values found in damped Ly-alpha systems (DLAs) along QSO sight lines, where only 10 out of 87 (~11%) have logN_FeII > 15.2. High FeII column densities are observed in the z=2.72 Lyman break galaxy cB58 (logN_FeII ~ 15.25) and in gamma-ray burst host galaxies (logN_FeII ~ 14.8-15.9). Using the global Schmidt law, that relates the SFR per unit area to the surface gas density, we derive logN_HI ~ 20.7. Assuming a moderate iron dust depletion (delta_Fe ~ 1 dex), we derive a mean metallicity Z/Z_sun = 2.2^{+2.7}_{-1.0} and an optical dust extinction A_V ~ 0.6. The high completeness of the GDDS sample implies that these results are typical of star-forming galaxies in the 1<z<2 redshift range, an epoch which has heretofore been particularly challenging for observational programs.

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