Broadband optical and IR spectral energy distributions are determined for spectroscopically confirmed z > 2 Lyman break objects in the Hubble Deep Field ( HDF ) .
These photometric data are compared to spectral synthesis models which take into account the effects of metallicity and of internal reddening due to dust .
It is found that , on average , Lyman break objects are shrouded in enough dust ( typically E ( B - V ) \approx 0.3 ) to suppress their UV fluxes by a factor of more than 10 .
The dust-corrected star formation rate in a typical HDF Lyman break object is \sim 60 h _ { 100 } ^ { -2 } M _ { \odot } yr ^ { -1 } ( q _ { 0 } = 0.5 ) .
Furthermore , these objects are dominated by very young ( \lesssim 0.2 Gyr , and a median of \sim 25 Myr ) stellar populations , suggesting that star formation at high redshift is episodic rather than continuous .
Typically , these star formation episodes produce \sim 10 ^ { 9 } h _ { 100 } ^ { -2 } M _ { \odot } of stars , or \sim \frac { 1 } { 20 } of the stellar mass of a present-day L ^ { * } galaxy .