We present a catalog of spectro-photometric 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 Å and 9500 Å are supplemented with U , J , H , and K _ { s } from various facilities , resulting in redshifts computed with \sim 40 spectral bins per galaxy .
For 81 galaxies between 0.5 < z < 1.5 with spectroscopic redshifts , the standard deviation in the fractional error in ( 1 + z ) is 0.046 .
With this catalog , we compute the B -band luminosity function in this redshift range from 72 galaxies .
Owing to the depth of the GRAPES survey , we are able to accurately constrain the faint-end slope by going to M _ { B } \simeq -18 mag at z = 1.0 \pm 0.2 , nearly two magnitudes fainter than previous studies .
The faint-end slope is \alpha = –1.32 \pm 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 .