A 3 μ[CLC]m[/CLC] Survey of the Chamaeleon I Dark Cloud

We describe an L -band photometric survey of ∼ 0.5 deg 2 of the Chamaeleon I dark cloud. The survey has a completeness limit of L < 11.0. Our survey detects 124 sources, including all known pre–main-sequence stars with L ≤ 11. The fraction of sources with near-IR excess emission is 58% ± 4% for K = 9–11. Cha I sources have bluer H - K and K - L colors than pre–main-sequence stars in Taurus-Auriga. These sources also have a strong correlation between EW(Hα) and K - L . Stars with K - L ≤ 0.6 have weak Hα emission; stars with K - L ≥ 0.6 have strong Hα emission. Because many Cha I sources are heavily reddened, this division between weak emission T Tauri stars and classical T Tauri stars occurs at a redder K - L than in Taurus-Auriga.