A SCUBA-2 850 micron survey of protoplanetary discs in the sigma Orionis cluster

TL;DR

This study uses 850 micron observations to analyze the dust and gas content of protoplanetary discs in the sigma Orionis cluster, revealing disc mass evolution over time and providing insights into planet formation stages.

Contribution

First large-scale submillimeter survey of sigma Orionis discs, offering new data on disc masses and evolution at an age of about 3 million years.

Findings

Detected 9 discs with masses 5-17 MJup

Mean disc mass for infrared excess sources is 0.5 MJup

Disc mass distribution differs from younger Taurus region

Abstract

We present the results from a large 850 micron survey of the sigma Orionis cluster using the SCUBA-2 camera on the James Clerk Maxwell Telescope. The 0.5-degree diameter circular region we surveyed contains 297 young stellar objects with an age estimated at about 3Myr. We detect 9 of these objects, 8 of which have infrared excesses from an inner disc. We also serendipitously detect 3 non-stellar sources at > 5sigma that are likely background submillimetre galaxies. The 9 detected stars have inferred disc masses ranging from 5 to about 17MJup, assuming similar dust properties as Taurus discs and an ISM gas-to-dust ratio of 100. There is a net positive signal toward the positions of the individually undetected infrared excess sources indicating a mean disc mass of 0.5 MJup . Stacking the emission toward those stars without infrared excesses constrains their mean disc mass to less than 0.3MJup, or an equivalent Earth mass in dust. The submillimetre luminosity distribution is significantly different from that in the younger Taurus region, indicating disc mass evolution as star forming regions age and the infrared excess fraction decreases. Submillimeter Array observations reveal CO emission toward 4 sources demonstrating that some, but probably not much, molecular gas remains in these relatively evolved discs. These observations provide new constraints on the dust and gas mass of protoplanetary discs during the giant planet building phase and provide a reference level for future studies of disc evolution.