First sub-arcsecond submillimeter-wave [C I] image of 49 Ceti with ALMA

TL;DR

This paper presents the first high-resolution images of the debris disk around 49 Ceti in [C I], CO, and dust continuum, revealing complex gas and dust distributions that inform models of debris disk gas origins.

Contribution

It provides the first sub-arcsecond [C I] imaging of 49 Ceti, revealing detailed gas and dust spatial distributions and their variations, which are crucial for understanding debris disk gas origins.

Findings

[C I] emission peaks inside the dust ring.

The [C I]/CO ratio varies significantly along the disk.

Enhanced [C I]/CO ratio near the star and outer disk.

Abstract

We present the first sub-arcsecond images of 49 Ceti in the [C I]3P1-3P0 emission and the 614 micron dust continuum emission observed with ALMA, as well as that in the CO(J=3-2) emission prepared by using the ALMA archival data. The spatial distribution of the 614 micron dust continuum emission is found to have a broad-ring structure with a radius of about 100 au around the central star. A substantial amount of gas is also associated with 49 Ceti. The [C I] emission map shows two peaks inside the dust ring, and its overall extent is comparable to that of the dust continuum emission and the CO emission. We find that the [C I]/CO(J=3-2) intensity ratio significantly varies along the major axis. The ratio takes the minimum value of 1.8 around the dust peak position, and increases inwards and outwards. The enhanced ratio around the central star (~3) likely originates from the stellar UV radiation, while that in the outer disk (~10) from the interstellar UV radiation. Such complex distributions of the [C I] and CO(J=3-2) emission will be a key to understand the origin of the gas in 49 Ceti, and will also provide a stringent constraint on physical and chemical models of gaseous debris disks.