Super-resolution Imaging of the Protoplanetary Disk Using Sparse Modeling

Masayuki Yamaguchi (University of Tokyo / Division of Science, NAOJ)


With an emphasis on improving the fidelity even in super-resolution regimes, new imaging techniques have been intensively developed over the last several years, which may provide substantial improvements to the interferometric observation of protoplanetary disks. The CLEAN technique has been widely used, but recently, a new technique using the sparse modeling (SpM) approach is suggested. This technique directly solves a set of undetermined equations and has been shown to behave better than the CLEAN technique based on mock observations with VLBI. However, it has never been applied to ALMA data. In this study, SpM is applied for the first time to observational data sets taken by the ALMA. The two data sets used in this study were taken independently using different array configurations at Band 7 (350 GHz), targeting the protoplanetary disk around HD 142527; one in the shorter-baseline array configuration (~ 430 m), and the other in the longer-baseline array configuration (~ 1570 m). The image resolutions reconstructed from the two data sets are different by a factor of ~ 3. We confirm that the previously known disk structures appear on the images produced by both SpM and CLEAN at the standard beam size. The image reconstructed from the shorter-baseline data using the SpM matches that obtained with the longer-baseline data using CLEAN, achieving a super-resolution image from which a structure finer than the beam size can be reproduced. Following up on the successful experimental application of the SpM, we apply the longer-baseline data set and find that there is a break at the position angle ~ 230 deg and the intensity distribution relays a double ridge-likee emission near this area. Our results demonstrate that on-going intensive development in the SpM imaging technique is beneficial to imaging with ALMA.

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