IAU01112
Presentation type requested: EITHER
THE STAR FORMATION RATE OF THE UNIVERSE AT REDSHIFT 6
Andrew J Bunker
Institute of Astronomy, University of Cambridge,UK
We determine the space density of UV-luminous star-burst galaxies at z~6 using deep HST/ACS SDSS-i' (F775W) and SDSS-z' (F850LP) and VLT ISAAC J- and Ks-band imaging of the Chandra Deep Field South. We find 8 galaxies [and one star] with (i'-z')>1.5 to a depth of z'(AB)=25.6. This corresponds to an unobscured star formation rate of ~15M_sun/yr/h_70^2 at z=5.9, equivalent to L* for the Lyman-break population at z=3-4 (Omega_Lambda=0.7, Omega_M=0.3). This measurement shows that at z~6 the star formation density at the bright end of the luminosity function is a factor of ~6 times less than that determined by Steidel et al. (1999) for a comparable sample of UV selected galaxies at z=3-4, and so extends our knowledge of the star formation history of the Universe to earlier times than previous work and into the epoch where reionization may have occurred. Our candidate z~6 galaxies have been presented in astro-ph/0302212 (Stanway, Bunker & McMahon; MNRAS - accepted) and we have obtained spectroscopic confirmation with DEIMOS on Keck of a z=5.78 galaxy selected with our i'-drop technique, demonstrating the validity of our approach (A. Bunker, E. Stanway, R. Ellis, R. McMahon & P. McCarthy, 2003 - submitted to ApJLett).
Stanway Elizabeth R, Mcmahon Richard G, Ellis Richard S, Mccarthy Patrick J
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