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[9.11] The Faint-End of the Galaxy Luminosity Function in the Leo I Group

K.P. Flint, M. Bolte, A.J. Metevier (UCO/Lick Observatory), C. Mendes de Oliveira (Instituto Astronomico e Geofisico, USP)

We present preliminary results from a wide-field survey of the Leo I Group for dwarf spheroidal (dSph) galaxies. Using 7 degrees²\ imaged with the KPNO MOSAIC+0.9m, we probe the faint-end of the R-band luminosity function well below the magnitude and surface brightness limits of existing surveys, with a target limiting absolute magnitude of M_lim = -10. We employ a detection method, based on work by Dalcanton et al. (1997, AJ, 114, 635), whereby we mask the images of all high-surface-brightness features, then convolve with a matched exponential filter for dSph-sized objects. Detection biases and completeness are fully determined by extensive Montecarlo simulations of artificial galaxies added to the real data frames. A typical Local Group dSph, if seen at the distance of Leo I (10 Mpc), will have a large angular size and a low surface brightness. Preliminary limits suggest we can detect the faintest and most diffuse Local Group dSphs -- Draco, Carina and Antlia -- with a 60-80% detection efficiency, and the smallest dwarf members -- Sextans and Ursa Minor -- with a ~40% detection efficiency. This work presents our technique and preliminary dwarf galaxy candidates from a 1\arcdeg \times 2\arcdeg\ subsample of our data.