I review some recent progress made in our understanding of galaxy evolution and the cosmic history of star formation .
The Hubble Deep Field ( HDF ) imaging survey has achieved the sensitivity to capture the bulk of the extragalactic background light from discrete sources .
No evidence is found in the optical number-magnitude relation down to AB = 29 mag for a large amount of star formation at high redshifts .
A census of the ultraviolet and blue “ dropouts ” , which requires the inclusion of the effects of intergalactic attenuation on the colors of cosmologically distant galaxies , appears to confirm this basic conclusion .
The emission history of the universe at ultraviolet , optical , and near-infrared wavelengths can be modeled from the present epoch to z \approx 4 by tracing the evolution with cosmic time of the galaxy luminosity density , as determined from several deep spectroscopic samples and the HDF .
The global spectrophotometric properties of field galaxies are well fitted by a simple stellar evolution model , defined by a time-dependent star formation rate ( SFR ) per unit comoving volume and a universal initial mass function which is relatively rich in massive stars .
The SFR density is found to rise sharply , by about an order of magnitude , from a redshift of zero to a peak value at z \approx 1.5 in the range 0.12–0.17 { M _ { \odot } yr ^ { -1 } Mpc ^ { -3 } } , to fall again by a factor of 2 ( 4 ) out of a redshift of 3 ( 4 ) .
Since only 10 % of the current stellar content of galaxies is produced at z > 2.5 , a rather low cosmic metallicity is predicted at these early times , in good agreement with the observed enrichment history of the damped Lyman- \alpha systems .
The biggest uncertainty is represented by the poorly constrained amount of starlight that was absorbed by dust and reradiated in the IR at early epochs .
A “ monolithic collapse ” scenario , where half of the present-day stars formed at z > 2.5 and were shrouded by dust , can be made consistent with the global history of light , but appears to overpredict the metal mass density at high redshifts .