A SUBARU PENCIL-BEAM SEARCH FORmR∼ 27 TRANS-NEPTUNIAN BODIES

We present the results of an archival search for trans-Neptunian objects (TNOs) in an ecliptic field observed with Subaru in 2002. The depth of the search allowed us to find 20 new TNOs with magnitudes between R = 24 and 27. We fit a double power-law model to the data; the most likely values for the bright and faint power-law exponents are α 1 = 0.73 +0.08 −0.09 and α 2 = 0.20 +0.12 −0.14 ; the differential number density at R = 23 is σ 23 = 1.46 +0.14 −0.12 and the break magnitude is R eq = 25.0 +0.8 −0.6 . This is the most precise measurement of the break in the TNO luminosity function to date. The break in the size distribution corresponds to a diameter of D = 90 ± 30 km assuming a 4% albedo.