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