Early Planet Formation in Embedded Disks (eDisk) IX: High-resolution ALMA Observations of the Class 0 Protostar R CrA IRS5N and its surrounding

TL;DR

This study uses high-resolution ALMA observations to analyze the early-stage protostar RCrA IRS5N, revealing a thick, smooth disk with Keplerian rotation and signs of ongoing material transfer, providing insights into initial planet formation conditions.

Contribution

First high-resolution ALMA imaging of IRS5N showing a thick, smooth protostellar disk with Keplerian rotation, and evidence of material transfer in a complex embedded environment.

Findings

Disk mass estimated between 0.007 and 0.02 M$_{ ext{sun}}$

Keplerian rotation around a 0.3 M$_{ ext{sun}}$ protostar

Material flow observed between binary components

Abstract

We present high-resolution, high-sensitivity observations of the Class 0 protostar RCrA IRS5N as part of the Atacama Large Milimeter/submilimeter Array (ALMA) large program Early Planet Formation in Embedded Disks (eDisk). The 1.3 mm continuum emission reveals a flattened continuum structure around IRS5N, consistent with a protostellar disk in the early phases of evolution. The continuum emission appears smooth and shows no substructures. However, a brightness asymmetry is observed along the minor axis of the disk, suggesting the disk is optically and geometrically thick. We estimate the disk mass to be between 0.007 and 0.02 M$_{\odot}$. Furthermore, molecular emission has been detected from various species, including C$^{18}$O (2$-$1), $^{12}$CO (2$-$1), $^{13}$CO (2$-$1), and H$_2$CO (3$_{0,3}-2_{0,2}$, 3$_{2,1}-2_{2,0}$, and 3$_{2,2}-2_{2,1}$). By conducting a position-velocity analysis of the C$^{18}$O (2$-$1) emission, we find that the disk of IRS5N exhibits characteristics consistent with Keplerian rotation around a central protostar with a mass of approximately 0.3 M$_{\odot}$. Additionally, we observe dust continuum emission from the nearby binary source, IRS5a/b. The emission in $^{12}$CO toward IRS5a/b seems to emanate from IRS5b and flow into IRS5a, suggesting material transport between their mutual orbits. The lack of a detected outflow and large-scale negatives in \tlvco~observed toward IRS5N suggests that much of the flux from IRS5N is being resolved out. Due to this substantial surrounding envelope, the central IRS5N protostar is expected to be significantly more massive in the future.