A model for collimated outflows in molecular clouds and the case of HH 7–11
Collimated outflows of high-velocity gas, with typical scale lengths of 0.01–0.2 pc, are often observed to be associated with linear chains of optical emission knots1, sometimes connected by faint nebulosities. The flows have been ascribed to the interaction between an energetic wind ejected by a young stellar object and circumstellar material. However, none of the acceleration and collimation mechanisms proposed so far can easily account for the most peculiar properties of the outflows, namely the almost constant spacing between the knots, their radial motion and the abrupt velocity changes along the flow, well illustrated by the prototype we use for our modelling, HH 7–11. We suggest here a new interpretation of the phenomenon, based on flows in a channel of variable cross-sectional area due to Kelvin–Helmholtz instabilities between the flow and the ambient medium; and present solutions of the Mach number equation for such a channel, which possess multiple critical points and shocks identified with the observed optical knots.
Molecular hydrogen mapping of Herbig–Haro 7–11; a filamentary bullet?
On presente une carte dans la raie d'emission H 2 associee a HH 7-11, et on discute de l'origine des objets de Herbig Haro
New insights into juvenile parotitis
Aim: We enquired about the possibility of a familial trend in juvenile parotitis and evaluated the role of SPINK1 mutations in juvenile parotitis.