File:Higuchi 2019 ApJ 883 180.pdf

English: We present the first subarcsecond images of 49 Ceti in the [C i] 3 P 1–3 P 0 emission and the 614 μm dust continuum emission observed with Atacama Large Millimeter/submillimeter Array (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 μm 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 inward and outward. The enhanced ratio around the central star (~3) likely originates from the stellar UV radiation, while that in the outer disk (~10) is from the interstellar UV radiation. Such complex distributions of the [C i] and CO(J = 3–2) emission will be key to understanding the origin of the gas in 49 Ceti, and will also provide a stringent constraint on physical and chemical models of gaseous debris disks.