Description
We present a catalog of spectrophotometric redshifts for 1308 galaxies from the Grism ACS Program for Extragalactic Science (GRAPES) observations with the Hubble Space Telescope. These low-resolution spectra between 6000{AA} and 9500{AA} are supplemented with U, J, H, and Ks data from various facilities, resulting in redshifts computed with ~40 spectral bins per galaxy. For 75 galaxies in the range 0.5<z<1.5 with spectroscopic redshifts, the standard deviation in the fractional error in 1+z is 0.037. With this catalog, we compute the B-band luminosity function in this redshift range from 72 galaxies. Due to the depth of the GRAPES survey, we are able to accurately constrain the faint-end slope by going to MB~-18mag at z=1.0+/-0.2, nearly 2mag fainter than previous studies. The faint-end slope is alpha=-1.32+/-0.07. When compared to numerous published values at various redshifts, we find strong evidence for a steepening of the faint-end slope with redshift, which is expected in the hierarchical formation scenario of galaxies.
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