HIGH-Z LY-ALPHA EMITTERS - I - A BLANK-FIELD SEARCH FOR OBJECTS NEAR REDSHIFT Z=3.4 IN AND AROUND THE HUBBLE DEEP FIELD AND THE HAWAII DEEPFIELD SSA-22

We present deep narrowband (lambda = 5390 Angstrom, Delta lambda = 77 Angstrom) and multicolor observations of the Hubble Deep Field and the Hawaii Deep Field SSA 22 obtained with the LRIS instrument at the 10 m Keek II Telescope. It is shown that there is a substantial populatio n of galaxies at z similar to 3.4 that can be selected by Ly alpha emi ssion. Comparison with color-selected samples shows that the samples s elected with these different criteria have substantial, but not comple te, overlap and that there is a comparable surface density in the two selected populations. The emission-line-selected samples include objec ts with strong Ly alpha, and which are significant contributers to the integrated star formation at these epochs. For a Salpeter initial mas s function, we estimate a minimum star formation rate of 0.01 M. Mpc(- 3) yr(-1) at z = 3.4 for H-0 = 65 km s(-1) Mpc(-1) and q(0) = 0.5 in t he Ly alpha-selected objects, though the value could be substantially higher if there is significant extinction.