Name/Affiliation: Cesar Briceno (Cerro Tololo Interamerican Observatory)
The low-mass pre-main sequence population of the Orion OB1 Association
I will present the results of our large scale photometric and spectroscopic census of the Orion OB1 association, spanning ~180 sq.deg. with emphasis on the wide off-cloud regions that contain somewhat older populations of stars in the age range ~4-10 Myr. With ~2000 confirmed T Tauri stars, this is the largest and most complete sample to date of low-mass young stars in this important evolutionary stage. We show that the off-cloud stellar population consists of various newly recognized clusters amidst a general low-density background, and that the ONC is surrounded by a few sq.deg. halo of young stars.