Star formation history of the hubble ultra deep field: Comparison with the hubble deep field-north

We use the NICMOS Treasury and ACS HUDF images to measure the extinction-corrected star formation history for 4681 galaxies in the region common to both images using the star formation rate distribution function and other techniques similar to those employed with the NICMOS and WFPC2 images in the HDFN. Unlike the HDFN, the NICMOS region of the HUDF appears to lack highly luminous and high star formation rate galaxies at redshifts beyond 3. The HUDF provides a region that is completely uncorrelated to the HDFN and therefore provides an independent measure of the star formation history of the universe. The combined HUDF and HDFN star formation rates show an average rate of 0.2 M_⊙ yr^-1 Mpc^-3. The average SFR of the combined fields at z = 1-3 is 0.29 M_⊙ yr^-1 Mpc ^-3, while the average at z = 4-6 is 1.2 M_⊙ yr ^-1 Mpc^-3. The SFRs at all redshifts are within 3 σ of the average over all redshifts.