The 158th Seminar on The Formation of Stars & Planets
Date & Time: 2021/August/20 (Fri) 17:00-18:30, Venue: Zoom TV Conference System. This is an informal seminar on the formation of stars and planets. We welcome anyone interested in the subject.
Title: "Ash-fall" induced by molecular outflow in protostar evolution
Abstract: Dust growth and its associated dynamics plays a key role in the first phase of planet formation in young stellar objects (YSOs). Observations have detected signs of dust growth in very young protoplanetary disks. Furthermore, signs of planet formation, gaps in the disk at a distance of several 10 astronomical units (AU) from the central protostar are also reported. From a theoretical point of view, however, it is not clear how planet form at the outer region of a disk despite the difficulty of rapid inward drift of dust so called radial drift barrier. Here, on the basis of three-dimensional magneto-hydrodynamical simulations of disk evolution with the dust growth, we propose a mechanism named "ash-fall" phenomenon induced by powerful molecular outflow driven by magnetic field which may circumvent the radial drift barrier. We found that the large dust which grows to a size of cm in the inner region of a disk is entrained by an outflow from the disk. Then large dust decoupled from gas is ejected from the outflow due to centrifugal force and is eventually fall onto the outer edge of the disk. The overall process is similar to behaviour of ash-fall from volcanic eruptions. In the ash-fall phenomenon, the Stokes number of dust increases by reasserting to the less dense disk outer edge. This may make the dusts overcome the radial drift barrier. Consequently, the ash-fall phenomenon can be a theoretical breakthrough to make the formation of planetesimals in outer region of the disk possible, and hence the formation of wide-orbit planets and the formation of the gaps.
次回：10/15 (金) 17:00-
連絡世話人：黒崎 健二（名古屋大学） kurosaki.k[at]nagoya-u.jp