2012AJ....143..102G

Smithsonian Hectospec Lensing Survey (SHELS) is a dense redshift survey covering a 4 deg² region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M_R= -13.3 + 5log h. We calculate the faint-end slope in the R band for the subset of SHELS galaxies with redshifts in the range 0.02 ≤ z < 0.1, SHELS_0.1. This sample contains 532 galaxies with R < 20.6 and with a median surface brightness within the half-light radius of SB_50, R_= 21.82 mag/arcsec2. We used this sample to make one of the few direct measurements of the dependence of the faint end of the galaxy luminosity function on surface brightness. For the sample as a whole the faint-end slope, α = -1.31±0.04, is consistent with both the Blanton et al. analysis of the Sloan Digital Sky Survey and the Liu et al. analysis of the COSMOS field. This consistency is impressive given the very different approaches of these three surveys. A magnitude-limited sample of 135 galaxies with optical spectroscopic redshifts with mean half-light surface brightness, SB_50, R_ ≥ 22.5 mag/arcsec2 is unique to SHELS_0.1. The faint-end slope is α_22.5= -1.52±0.16. SHELS_0.1 shows that lower surface brightness objects dominate the faint-end slope of the luminosity function in the field, underscoring the importance of surface brightness limits in evaluating measurements of the faint-end slope and its evolution.