OPTICAL-INFRARED SPECTRAL ENERGY-DISTRIBUTIONS OF Z-GREATER-THAN-2 LYMAN BREAK GALAXIES

Broadband optical and IR spectral energy distributions are determined for spectroscopically confirmed z > 2 Lyman break objects in the Hubbl e Deep Field (HDF). These photometric data are compared with spectral synthesis models which take into account the effects of metallicity an d of internal reddening due to dust. It is found that, on average, Lym an break objects are shrouded in enough dust [typically E(B-V) approxi mate to 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 ob ject is similar to 60 h(100)(-2) M. yr(-1) (q(0) = 0.5). Furthermore, these objects are dominated by very young (less than or similar to 0.2 Gyr, and a median of similar to 25 Myr) stellar populations, suggesti ng that star formation at high redshift is episodic rather than contin uous. Typically, these star formation episodes produce similar to 10(9 ) h(100)(-2) M. of stars, or similar to 1/20 of the stellar mass of a present-day L galaxy.