Early Planet Formation in Embedded Disks (eDisk). I. Overview of the Program and First Results

Abstract

We present an overview of the Large Program, “Early Planet Formation in Embedded Disks (eDisk),” conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The ubiquitous detections of substructures, particularly rings and gaps, in protoplanetary disks around T Tauri stars raise the possibility that at least some planet formation may have already started during the embedded stages of star formation. In order to address exactly how and when planet formation is initiated, the program focuses on searching for substructures in disks around 12 Class 0 and 7 Class I protostars in nearby (<200 pc) star-forming regions through 1.3 mm continuum observations at a resolution of ∼7 au (0.″04). The initial results show that the continuum emission, mostly arising from dust disks around the sample protostars, has relatively few distinctive substructures, such as rings and spirals, in marked contrast to Class II disks. The dramatic difference may suggest that substructures quickly develop in disks when the systems evolve from protostars to Class II sources, or alternatively that high optical depth of the continuum emission could obscure internal structures. Kinematic information obtained through CO isotopologue lines and other lines reveals the presence of Keplerian disks around protostars, providing us with crucial physical parameters, in particular, the dynamical mass of the central protostars. We describe the background of the eDisk program, the sample selection and their ALMA observations, and the data reduction, and we also highlight representative first-look results.

Early Planet Formation in Embedded Disks (eDisk). IV. The Ringed and Warped Structure of the Disk around the Class I Protostar L1489 IRS

“…L1489 IRS was observed as part of the eDisk Large Program (project code: 2019.1.00261.L, PI: N. Ohashi) and a dedicated Directors Discretionary Time (DDT) program (project code: 2019.A.00034.S, PI: J. J. Tobin). Details of the observations and data reduction procedures are provided in Ohashi et al (2023). Here we summarize the key aspects specific to L1489 IRS.…”

“…The eDisk program is designed to observe the dust continuum at 1.3 mm (or 225 GHz), as well as several molecular lines. The targeted molecular lines are listed in Table 2 of Ohashi et al (2023). In this specific first-look paper on L1489 IRS, we focused on three molecular lines: 13 CO J = 2-1, C 18 O J = 2-1, and SO J N = 6 5 -5 4 .…”

“…In this specific first-look paper on L1489 IRS, we focused on three molecular lines: 13 CO J = 2-1, C 18 O J = 2-1, and SO J N = 6 5 -5 4 . In addition to these lines, several other lines ( 12 CO, DCN, H 2 CO, and c-C 3 H 2 ) are also detected, while SiO and CH 3 OH lines are not detected (see Table 2 in Ohashi et al 2023, for the complete list of the targeted transitions).…”

“…Motivated by these previous studies, the Early Planet Formation in Embedded Disks (eDisk) ALMA Large Program (Ohashi et al 2023) was initiated with the main goal of understanding how early substructures form in the disks around young protostars. The core of eDisk is a high-resolution systematic survey of the dust continuum substructures down to ∼5 au scales in 19 young embedded sources.…”

“…Thus, in the present work, we assume that the distance to L1489 IRS is 146 pc 21 . When this distance as well as the updated photometry from near-infrared to millimeter wavelengths is taken into account, the bolometric luminosity and bolometric temperature are 3.4 L e and 213 K, respectively (Ohashi et al 2023), from which L1489 IRS is classified as a Class I source.…”