Survey of Orion Disks with ALMA (SODA)

Abstract

Context. Surveys of protoplanetary disks in nearby star-forming regions (SFRs) have provided important information on their demographics. However, due to their sample sizes, these surveys cannot be used to study how disk properties vary with the environment. Aims. We conduct a survey of the unresolved millimeter continuum emission of 873 protoplanetary disks identified by Spitzer in the L1641 and L1647 regions of the Orion A cloud. This is the largest such survey yet, allowing us to identify even weak trends in the median disk mass as a function of position in the cloud and cluster membership. The sample detection rates and median masses are also compared to those of nearby (<300 pc) SFRs. Methods. The sample was observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 225 GHz, with a median rms of 0.08 mJy beam−1, or 1.5 M⊕. The data were reduced and imaged using an innovative parallel data processing approach. Results. We detected 58% (502/873) of the observed disks. This includes 20 disks with dust masses >100 M⊕, and two objects associated with extended dust emission. By fitting a log-normal distribution to the data, we infer a median disk dust mass in the full sample of 2.2−0.2+0.2 M⊕. In L1641 and L1647, median dust masses are 2.1−0.2+0.2M⊕ and 2.6−0.5+0.4M⊕, respectively. Conclusions. The disk mass distribution of the full sample is similar to that of nearby low-mass SFRs at similar ages of 1–3 Myr. We find only weak trends in disk (dust) masses with galactic longitude and between the Young Stellar Object (YSO) clusters identified in the sample, with median masses varying by ≲50%. Differences in age may explain the median disk mass variations in our subsamples. Apart from this, disk masses are essentially constant at scales of ~100 pc. This also suggests that the majority of disks, even in different SFRs, are formed with similar initial masses and evolve at similar rates, assuming no external irradiation, with disk mass loss rates of ~10−8 M⊙ yr−1.