We investigate the structure of accretion disks around massive protostar
applying steady state models of thin disks. The thin disk equations are solved
with proper opacities for dust and gas taking into account the huge temperature
variation along the disk. We explore a wide parameter range concerning stellar
mass, accretion rate, and viscosity parameter \alpha . The most essential
finding is a very high temperature of the inner disk. For e.g. a 10 M_sun
protostar and an accretion rate of 10^-4 M_sun/yr, the disk midplane
temperature may reach almost 10^5 K. The disk luminosity in this case is about
10^4 L_sun and, thus, potentially higher than that of a massive protostar. We
motivate our disk model with similarly hot disks around compact stars. We
calculate a dust sublimation radius by turbulent disk self-heating of more than
10AU, a radius, which is 3 times larger than caused by stellar irradiation. We
discuss implications of this result on the flashlight effect and the
consequences for the radiation pressure of the central star. In difference to
disks around low mass protostars our models suggest rather high values for the
disk turbulence parameter \alpha close to unity. However, disk stability to
fragmentation due to thermal effects and gravitational instability would
require a lower \alpha value. For \alpha = 0.1 we find stable disks out to
80AU. Essentially, our model allows to compare the outer disk to some of the
observed massive protostellar disk sources, and from that, extrapolate on the
disk structure close to the star which is yet impossible to observe.Comment: 23 pages, 8 figures, accepted by ApJ, For full version see
http://www.mpia.de/homes/vaidya