  We study the evolution of the galaxy UV luminosity density as a function of
redshift in the Hubble Deep Field North (HDF-N). We estimate the amount of
energy absorbed by dust and hidden from optical observations by analyzing the
HDF-N photometric data with the spectral energy distribution fitting method.
According to our results, at redshifts 1 < z < 4.5, the global energy observed
in the UV rest-frame at lambda=1500 A corresponds to only 7-11% of the stellar
energy output, the rest of it being absorbed by dust and re-emitted in the
far-IR. Our estimates of the comoving star formation rate density in the
universe from the extinction-corrected UV emission are consistent with the
recent results obtained with Submillimeter Common-User Bolometer Array
  (SCUBA) at faint sub-millimeter flux levels.
