A Three Micron Survey of the Chamaeleon I Dark Cloud

Abstract

We describe an L-band photometric survey of 0.5 square deg of the Cha 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(H-alpha) and K-L. Stars with K-L < 0.6 have weak H-alpha emission; stars with K-L > 0.6 have strong H-alpha 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.