SCUBA Maps of Massive CS Cores in the Mon OB1 Dark Cloud

Although details of the formation of isolated low-mass stars are not complete, a fairly well-understood broad picture has emerged in recent years. In contrast, the formation of stars in high-mass cores is poorly understood. In order to investigate the masses and evolutionary stages of stars forming in massive cores, we are undertaking a complete SCUBA survey of the massive CS cores in the Mon OB1 dark cloud (Wolf-Chase, Walker, & Lada 1995, ApJ 442, 197 [WWL95]). This figure presents our 850 micron map of one of these cores (SCL: WWL95), and helps elucidate the presence of a number of individual clumps within the core, as well as more extended dust emission. Well-sampled spectral energy distributions (SEDs) are required to characterize these clumps and to distinguish between evolutionary classes of Young Stellar Objects (YSOs), but current determinations of SEDs are extremely limited: there are few sets of measured SEDs that cover a significant range in protostellar mass, evolutionary class, and the complete wavelength range from the mid-infrared to the submillimetre. A useful constraint on the evolutionary class of a protostar is the presence, size, and energetics of an outflow. In the Mon OB1 dark cloud, we have a unique opportunity to study the properties of YSOs that are forming in massive CS cores (WWL95), and for which we have a complete survey of outflows (Margulis, Lada, & Snell 1998, ApJ, 333, 316; Wolf-Chase, Moriarty-Schieven, Fich, & Barsony, in preparation).

Many YSO SEDs have been constructed from low-resolution IRAS data. We have created a technique using high-iteration HIRES-processing and modeling of IRAS data together with SCUBA data that has been very useful in extracting multiple source SEDs in confused regions (Aumann, Fowler, & Melnyk 1990, AJ, 99, 1674; Hurt & Barsony 1996, ApJL, 460, L45; Barsony et al. 1998, ApJ, 509, 733; O'Linger et al. 1999, ApJ, 515, 696; Wolf-Chase, Moriarty-Schieven, Fich, & Barsony, in preparation). Our completed SCUBA survey will allow us to construct new SEDs for all of the YSOs in the CS cores, which will allow determination of the physical parameters and evolutionary stages of the stars forming in these cores, and will allow a preliminary investigation into the question of whether massive cores necessarily form higher-mass stars. Questions such as this can only be addressed by studying YSOs that are still deeply embedded in their natal cloud cores. Once a YSO has reached the pre-main sequence stage, many of these cores have already been dispersed (e.g., WWL95; Wolf-Chase & Walker 1995, ApJ, 447, 244).