A WISE CENSUS OF YOUNG STELLAR OBJECTS IN THE PERSEUS OB2 ASSOCIATION

We have performed a Wide-Field Infrared Survey Explorer based study to identify and characterize young stellar objects (YSOs) in the 12 degrees x 12 degrees Perseus OB2 association. A spectral energy distribution (SED) slope in the range of 3.4-12 mu m and 5 sigma selection criteria were used to select our initial sample. Further manual inspection reduced our final catalog to 156 known and 119 YSO candidates. The spatial distribution of newly found YSOs all over the field shows an older generation of star formation in which most of its massive members have evolved into main-sequence stars. In contrast, the majority of younger members lie within the Perseus molecular cloud and currently active star-forming clusters such as NGC 1333 and IC 348. We also identified an additional 66 point sources that passed YSO selection criteria but are likely AGB stars. However, their spatial distribution suggests that they may contain a fraction of the YSOs. Comparing our results with the commonly used color-color selections, we found that while the color selection method fails in picking up bright but evolved weak disks, our SED fitting method can identify such sources, including transitional disks. In addition, we have less contamination with background sources such as galaxies, but at a price of losing fainter (J(mag) > 12) YSOs. Finally, we employed a Bayesian Monte Carlo SED fitting method to determine the characteristics of each YSO candidate. Distribution of SED slopes and model-driven age and mass confirms separated YSO populations with three suggested age groups of younger than 1 Myr old, 1-5 Myr old, and older than 5 Myr, which agrees with the age of the Per OB2 association and currently star-forming sites within the cloud.