Missing water in Class I protostellar disks

Turbulence in Class 0 and Class I protostellar envelopes

We estimate the levels of turbulence in the envelopes of Class 0 and I protostars using a model based on measurements of the peak separation of double-peaked asymmetric line profiles. We use observations of 20 protostars of both Class 0 & I taken in the HCO(J=3→2) line that show the classic double-peaked profile. We find that some Class 0 sources show high levels of turbulence whilst others dem...

Transport Processes in Protostellar Disks

Magnetohydrodynamics of Protostellar Disks

The magnetohydrodynamical behavior (MHD) of accretion disks is reviewed. A detailed presentation of the fundamental MHD equations appropriate for protostellar disks is given. The combination of a weak (subthermal) magnetic field and Keplerian rotation is unstable to the magnetorotational instability (MRI), if the degree of ionization in the disk is sufficiently high. The MRI produces enhanced a...

Dust Evolution in Protostellar Accretion Disks

We calculated the collapse of a / r 2 density peaked, slowly rotating molecular cloud core by 2D numerical radiation hydrodynamical simulations. The dynamics of the dust grains is calculated applying a multicomponent uid model. Acceleration by the radiation eld, coupling to the gas component by dynamical friction, coagulation and shattering of the grains is included. Relative velocities between...

ON PROTOSTELLAR DISKS IN HERBIG AeyBe STARS

The spectral shape of IR emission from Herbig AeyBe stars has been invoked as evidence for accretion disks around high-mass protostars. Instead, we present here models based on spherical envelopes with an r dust density profile that successfully explain the observed spectral shapes. The spectral energy distributions of eight primary candidates for protostellar disks are fitted in detail for all...