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We present Karl G. Jansky Very Large Array 1.3, 3.6, and 6 cm continuum maps of compact radio sources in the Orion Nebular Cluster (ONC). We mosaicked 34 arcmin2 at 1.3 cm, 70 arcmin2 at 3.6 cm and 109 arcmin2 at 6 cm, containing 778 near-infrared detected young stellar objects and 190 Hubble Space Telescope-identified proplyds (with significant overlap between those characterizations). We detected radio emission from 175 compact radio sources in the ONC, including 26 sources that were detected for the first time at these wavelengths. For each detected source, we fitted a simple free–free and dust emission model to characterize the radio emission. We extrapolate the free–free emission spectrum model for each source to ALMA bands to illustrate how these measurements could be used to correctly measure protoplanetary disk dust masses from submillimeter flux measurements. Finally, we compare the fluxes measured in this survey with previously measured fluxes for our targets, as well as four separate epochs of 1.3 cm data, to search for and quantify the variability of our sources. [ABSTRACT FROM AUTHOR]

We present ALMA observations of the largest protoplanetary disk in the Orion Nebula, 114–426. Detectable 345 GHz (856 μm) dust continuum is produced only in the 350 AU central region of the ∼1000 AU diameter silhouette seen against the bright background in Hubble Space Telescope images. Assuming optically thin dust emission at 345 GHz, a gas-to-dust ratio of 100, and a grain temperature of 20 K, the disk gas-mass is estimated to be Jupiter masses. If most solids and ices have been incorporated into large grains, however, this value is a lower limit. The disk is not detected in dense-gas tracers such as HCO+J = 4–3, HCN J = 4–3, or CS = 7–6. These results may indicate that the 114–426 disk is evolved and depleted in some light organic compounds found in molecular clouds. The CO J = 3–2 line is seen in absorption against the bright 50–80 K background of the Orion A molecular cloud over the full spatial extent and a little beyond the dust continuum emission. The CO absorption reaches a depth of 27 K below the background CO emission at VLSR 6.7 km s ∼ 0.″52 (210 AU) northeast and 12 K below the background CO emission at VLSR ≈ 9.7 km s ∼ 0.″34 (140 AU) southwest of the suspected location of the central star, implying that the embedded star has a mass less than 1 M. [ABSTRACT FROM AUTHOR]

We present the results from a Submillimeter Array survey of the 887 μm 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 ∼5 to 330 mJy; upper limits (at 3σ) for the other 73 sources range from 3 to 24 mJy. For standard assumptions, the corresponding disk masses range from ∼0.003 to 0.2 , with upper limits at 0.002–0.01 . 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. [ABSTRACT FROM AUTHOR]