The structure and dynamics of the proto-planetary nebula M1-92

We present high-resolution (1." 0) maps of (CO)-C-13 J = 2-1 in the proto-p lanetary nebula M1-92, Minkowski's Footprint, obtained with the Institut de Radioastronomie Millimetrique (IRAM) interferometer at Plateau de Bure. We confirm the main components found in our previous works: a central disklik e condensation, a bipolar double-shell structure with axial outward velocit y increasing with the distance to the star, and two opposed features at the tips of the nebula where the maximal deprojected velocity is attained, sim ilar to 70 km s(-1). The major quality of the present data allows us to est imate the very small width of the double-shell walls, similar to 0." 6 (2 x 10(16) cm), and the diameter of the central disk, 2 "-3 " (10(17) cm). The whole structure is probably the remnant of the previous asymptotic giant b ranch (AGE) shell after being shocked by the bipolar post-AGE jets. The mas s of the molecular envelope is about 0.9 M-., and its kinetic momentum and energy (released by the wind interaction) are similar to 3 x 10(39) g cm s( -1) and similar to 7 x 10(45) ergs, respectively. Since the interaction tim e must be significantly smaller than the age of the nebula, 900 yr, these f igures imply very energetic post-AGE jets that cannot be driven by radiatio n pressure. We also notice that the inner disklike structure is too large f or collimating the very narrow post-AGB jets. We propose that reaccretion o f material, ejected during the previous AGE phase, is the most likely mecha nism to explain the strongly bipolar and very energetic post-AGE ejections.