The Missing Intermediate Luminosity Galaxies in the Leo I Group

We present results from a large scale R-band survey of the nearby Leo I group to measure the luminosity function down to dwarf spheroidal luminosities and surface brightnesses. This program has utilized>7 square degrees of imaging with the Mosaic camera at the KPNO 0.9mand extensive, on-going spectroscopic follow-up. We estimate our completeness from simulations to be 90% at μ_R(0) ≃ 24.5, M _R ≃ –11.Leo I is a nearby, low-density group for which a steep faint-end slope has been suggested (Ferguson and Sandage, 1991).We find the luminosity function to be more similar to that of the Local Group at the faint-end (flat).We also find an unusual gap in the luminosity function at intermediate luminosities, –19.5 < M _R < –16. This gap cannot be explained by pure Poisson fluctuations around a typical Schechter function, nor is it likely to result from photometric incompleteness. This revised version was published online in July 2006 with corrections to the Cover Date.