Early Planet Formation in Embedded Disks (eDisk)

XX. Constraining the chemical tracers of young protostellar sources

¹ Niels Bohr Institute, University of Copenhagen, Jagtvej 155A, 2200 Copenhagen N., Denmark
² Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109-1107, USA
³ Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USA
⁴ Department of Physics and Astronomy, SNU Astronomy Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea
⁵ Department of Astronomy, Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan
⁶ Dipartimento di Fisica e Astronomia, Università di Bologna, Via Gobetti 93/2, 40122 Bologna, Italy
⁷ Star and Planet Formation Laboratory, RIKEN Pioneering Research Institute, Wako-shi, Saitama 351-0106, Japan
⁸ Institute of Astronomy and Astrophysics, Academia Sinica. 11F of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Rd, Taipei 106319, Taiwan, ROC
⁹ National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA
¹⁰ University of Virginia, 530 McCormick Rd., Charlottesville, VA 22904, USA
¹¹ Department of Astronomy, University of Illinois, 1002 West Green St, Urbana, IL 61801, USA
¹² Institute for Astronomy, University of Hawaiì at Mānoa, 2680 Woodlawn Dr., Honolulu, HI 96822, USA

^★ Corresponding author: rajeeb.sharma@nbi.ku.dk

Received: 10 January 2025
Accepted: 3 September 2025

Abstract

Context. Recent studies indicate that the formation of planets in protoplanetary disks begins early in the embedded Class 0/I phases of protostellar evolution. The physical and chemical makeup of the embedded phase can provide valuable insights into the process of star and planet formation.

Aims. This study aims to provide a thorough overview of the various morphologies for molecular emissions observed on disk scales (≲100 au) toward nearby embedded sources.

Methods. We present high angular resolution (0_⋅^′′1, ~ 15 au) molecular line emissions for ¹²CO, ¹³CO, C¹⁸O, SO, SiO, DCN, CH₃OH, H₂CO, and c–C₃H₂ toward 19 nearby protostellar sources in the context of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program “Early Planet Formation in Embedded Disks (eDisk).”

Results. Emissions in ¹²CO are seen toward all sources and primarily trace outflowing materials. A few sources also show high-velocity jets in SiO emission and high-velocity channel maps of ¹²CO. The ¹³CO and C¹⁸O emissions are well-known tracers of high-density regions and trace the inner envelope and disk regions with clear signs of rotation seen at continuum scales. The large-scale emissions of ¹³CO also delineate the outflow cavity walls where the outflowing and infalling materials interact with each other, and exposure to UV radiation leads to the formation of hydrocarbons such as c–C₃H₂. Both DCN and CH₃OH, when detected, show compact emissions from the inner envelope and disk regions that peak at the position of the protostar. The CH₃OH emissions are contained within the region of DCN emissions, which suggests that CH₃OH traces the hot core regions. Likewise, a few sources, also display emissions in CH₃OH toward the outflow. Both SO and H₂CO show complex morphology among the sources, suggesting that they are formed through multiple processes in protostellar systems.