The Dispersed Population of Dusty Young Stellar Objects in the Orion OB1 Association

B. Mazur1, T. Megeath1, R. Gutermuth2, C. Briceno3, J. Hernandez3, J. Stauffer4

1: U. of Toledo; 2: U. of Mass; 3: CIDA, Venezuela; 4: Spitzer Science Center

Following the exhaustion of the cryogenic fluids, a `warm’ mission survey extended the of the off-cloud region in the Orion/OB1 association complex. These data supplement the existing surveys of the σ Orionis cluster and OB1b fields.

Assemble a photometric catalogue of the extended region using Spitzer augmented with available 2MASS and WISE data. • Using only the three 2MASS bands and two IRAC bands at 3.6μm and 4.5μm, we estimate a recovered fraction of between 90 − 70%, when compared to the 3 + 4 band detections. • Using disc fractions measured by Hernandez et al. 2007, one can estimate a total off-cloud population, excluding the σ Orionis cluster, 3000 − 8500 young stars.

110 sigma Ori

700 OB1b

Recovered fractions: ~90% in σ Ori~70% in OB1b

Disc fractions from Hernandez (2007a,b):OB1b: ~13%σ Ori: ~ 35%

Estimated Population (excluding σ Ori):3500 - 8000