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 offcloud 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