Speaker
Description
Substructures are ubiquitous --- nearly 60\% of protostellar disks, which is less than 1 Myr, host features such as rings/gaps, spirals, and crescents. These features are widely interpreted as evidence for embedded giant planets, suggesting that planet formation occurs much earlier than previously thought. However, previous observations have been biased toward bright, large disks, even though small disks dominate statistically. This prompts the question: `Do small protostellar disks possess substructures in their disks?'
\medskip
As an extension of the ALMA Large Program Early Planet Formation in Embedded Disks (eDisk), we are conducting a survey of a homogeneous sample of 25 protostars in the Ophiuchus star-forming region (eDisk@Oph). By focusing on a single star-forming region, rather than combining samples from regions at different distances, we minimize uncertainties and biases arising from variations in sample completeness and environment. In this sub-project, we analyze dust continuum emission of protostellar disks using sparse modeling (SpM). The application of SpM has revealed sharper substructures---such as additional rings, gaps, and spirals---even in compact or marginally resolved disks, demonstrating its capability for super-resolution reconstruction.
\medskip
Our sample comprises 25 protostellar disks, including 11 large (with radii $> 20$ au) and 14 small disks ($< 20$ au). Among large disks, three substructures have been already known. To statistically assess whether the occurrence rates of substructures in small and large protostellar disks differ significantly, we use Fisher’s exact test. If the number of detected substructures in small disks is below 9, the two populations of small and large protostellar disks will be considered statistically consistent at the commonly used significance level of 0.05. Conversely, detecting more than 10 substructures would indicate that the two populations are significantly different. This could imply that planet formation is more efficient in small protostellar disks than in large ones.
\medskip
By applying SpM, the spatial resolution improves to approximately 20 mas (2.8~au), compared to $\sim$100 mas (14 au) obtained with the CLEAN algorithm, the standard image reconstruction method in radio astronomy. As a result, we newly identify three substructures in small disks that are not recovered by CLEAN. We tentatively concluded that the substructures are also a universal characteristic in small protostellar disks. In my talk, I will also present the update in data analysis.
| Participate the oral/poster presentation award competition | No |
|---|