First detection of submillimeter-wave [13C I] 3P1-3P0 emission in a gaseous debris disk of 49 Ceti with ALMA

TL;DR

This study reports the first detection of [13C I] emission in a debris disk around 49 Ceti using ALMA, revealing optically thick [C I] emission and providing insights into carbon isotope ratios in such environments.

Contribution

First detection of [13C I] 3P1-3P0 emission in a debris disk, demonstrating optical thickness of [C I] emission and advancing understanding of carbon isotopic composition.

Findings

[13C I] detected in 49 Ceti debris disk

[C I]/[13C I] ratio is 12+-3, indicating optical thickness

First [13C I] detection in debris disks and interstellar medium

Abstract

We have detected the submillimeter-wave fine-structure transition (3P1-3P0) of 13C, [13C I], in the gaseous debris disk of 49 Ceti with the Atacama Large Millimeter/submillimeter Array (ALMA). Recently, the [C I] 3P1-3P0 emission has been spatially resolved in this source with ALMA. In this dataset, the F=3/2-1/2 hyperfine component of [13C I], which is blue-shifted by 2.2 km/s from the normal species line, [C I], has been identified in the outer part of the 49 Ceti disk, thanks to the narrow velocity widths of the gas components. The [C I]/[13C I] line intensity ratio is found to be 12+-3, which is about one-fifth of the 12C/13C abundance ratio of 77 in the interstellar medium. This result clearly reveals that the [C I] emission is optically thick in 49 Ceti at least partly, as speculated by the previous work. As far as we know, this is the first detection of [13C I] 3P1-3P0 emission at 492 GHz not only in debris disks but also in the interstellar medium.