Lyman‐Break Galaxies at aastex amsbsy amsfonts amssymb bm mathrsfs pifont stmaryrd textcomp portland, xspace amsmath, amsxtra 2, OT1fontenc wncyr 2 empty 10976 document z 4 document and the Evolution of the Ultraviolet Luminosity Density at High Redshift

We present initial results of a survey for star-forming galaxies in the redshift range 3.8 =4.13. Selecting these galaxies in a manner entirely analogous to our large survey for Lyman break galaxies at smaller redshift (2.7 1 once internally consistent corrections for dust are made. This suggests that there is no obvious peak in star formation activity, and that the onset of substantial star formation in galaxies occurs at z > 4.5. abridged abstract