ALMA Observations of the Orion Proplyds

Abstract

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of protoplanetary disks ("proplyds") in the Orion Nebula Cluster. We imaged five individual fields at 856 μm containing 22 Hubble Space Telescope (HST)-identified proplyds and detected 21 of them. Eight of those disks were detected for the first time at submillimeter wavelengths, including the most prominent, well-known proplyd in the entire Orion Nebula, 114-426. Thermal dust emission in excess of any free-free component was measured in all but one of the detected disks, and ranged between 1 and 163 mJy, with resulting disk masses of 0.3-79 M_(jup). An additional 26 stars with no prior evidence of associated disks in HST observations were also imaged within the 5 fields, but only 2 were detected. The disk mass upper limits for the undetected targets, which include OB stars, θ^1 Ori C, and θ^1 Ori F, range from 0.1 to 0.6 M_(jup). Combining these ALMA data with previous Submillimeter Array observations, we find a lack of massive (≳3 M_(jup)) disks in the extreme-UV-dominated region of Orion, within 0.03 pc of θ^1 Ori C. At larger separations from θ^1 Ori C, in the far-UV-dominated region, there is a wide range of disk masses, similar to what is found in low-mass star forming regions. Taken together, these results suggest that a rapid dissipation of disk masses likely inhibits potential planet formation in the extreme-UV-dominated regions of OB associations, but leaves disks in the far-UV-dominated regions relatively unaffected.