The z 4 Lyman break galaxies: Colors and theoretical predictions
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We investigate several fundamental properties of z 4 Lyman break galaxies by comparing observations with the predictions of a semianalytic model based on the cold dark matter theory of hierarchical structure formation. We use a sample of B435-dropouts from the Great Observatories Origins Deep Survey and complement the Advanced Camera for Surveys optical B 435, V606, i775, and z850 data with the Very Large Telescope Infrared Spectrometer and Array Camera J, H, and K s observations. We extract B435-dropouts from our semianalytic mock catalog using the same color criteria and magnitude limits that were applied to the observed sample. We find that the i 775-Ks, colors of the model-derived and observed B 435-dropouts are in good agreement. However, we find that the i 775-z850 colors differ significantly, indicating perhaps that either too little dust or an incorrect extinction curve has been used. Motivated by the reasonably good agreement between the model and observed data, we present predictions for the stellar masses, star formation rates, and ages for the z 4 Lyman break sample. We find that according to our model, the color selection criteria used to select our z 4 sample surveys 67% of all galaxies at this epoch down to z850 < 26.5. We find that our model predicts a 40% mass buildup between the z 4 and z 3 epochs for the UV rest-frame L* galaxies. Furthermore, according to our model, at least 50% of the total stellar mass resides in relatively massive UV-faint objects that fall below our observational detection limit.
