PROTOPLANETARY DISK MASSES IN THE YOUNG NGC 2024 CLUSTER

We present the results from a Submillimeter Array survey of the 887 mu m continuum emission from the protoplanetary disks around 95 young stars in the young cluster NGC 2024. Emission was detected from 22 infrared sources, with flux densities from similar to 5 to 330 mJy; upper limits (at 3 sigma) for the other 73 sources range from 3 to 24 mJy. For standard assumptions, the corresponding disk masses range from similar to 0.003 to 0.2 M-circle dot, with upper limits at 0.002-0.01 M-circle dot. The NGC 2024 sample has a slightly more populated tail at the high end of its disk mass distribution compared to other clusters, but without more information on the nature of the sample hosts it remains unclear if this difference is statistically significant or a superficial selection effect. Unlike in the Orion Trapezium, there is no evidence for a disk mass dependence on the (projected) separation from the massive star IRS 2b in the NGC 2024 cluster. We suggest that this is due to either the cluster youth or a comparatively weaker photoionizing radiation field.