Sgr A* is extra-ordinarily dim in all wavelengths requiring a very low accretion rate at the present time. However, at a radial distance of a fraction of a parsec from Sgr A*, two rings populated by young massive stars suggest a recent burst of star formation in a rather hostile environment. Here we explore two ways of creating such young stellar rings with a gaseous accretion disk: by self-gra...

Numerous studies over the past 30 years have suggested there is a causal connection between the motion of the Sun through the Galaxy and terrestrial mass extinctions or climate change. Proposed mechanisms include comet impacts (via perturbation of the Oort cloud), cosmic rays and supernovae, the effects of which are modulated by the passage of the Sun through the Galactic midplane or spiral arm...

High-resolution observations of edge-on proto-planetary disks in emission from molecular species sampling different critical densities and formation pathways offer the opportunity to trace vertical chemical physical structures protoplanetary disks. Based on analysis sub-arcsecond resolution Atacama Large Millimeter Array (ALMA) archival data for Flying Saucer disk (2MASS J16281370-2431391), we ...

Abstract We study the long-term radial transport of micron to millimeter-size grains in protostellar disks (PSDs) based on diffusion and viscosity coefficients measured from 3D global stratified-disk simulations with a Lagrangian hydrodynamic method. While gas drag tends dust species radially inwards, stochastic can spread considerable fraction outwards (upstream) depending nature turbulence. I...

Context. In cold and shielded environments, molecules freeze out on dust grain surfaces to form ices such as H 2 O, CO, CO , CH 4 3 OH, NH . protoplanetary disks, conditions are present in the midplane regions beyond snowline, but exact radial vertical extension depend disk mass, geometry, stellar ultra-violet irradiation. Aims. The goal of this work is a computationally efficient method comput...

The composition of forming planets is strongly affected by the protoplanetary disc's thermal structure. This structure predominantly set dust radiative transfer and viscous (accretional) heating can be impacted gaps - regions low gas density that occur when form. effect variations in surface on disc temperature has been poorly understood until now. In this work, we use code MCMax to model 2D wi...

In theory of accretion disks, angular momentum and mass transfer are associated with the generation of energy through viscous dissipation. In the construction of SED models of protostellar disks, the stellar irradiation is usually assumed to be the dominant heating source. Here we construct a new set of self-consistent analytical disk models by taking into account both sources of thermal energy...

We present the first 3.8 µm image of the dusty ring surrounding the young binary system GG Tau, obtained with the W. M. Keck II 10 m telescope's adap-tive optics system. This is the longest wavelength at which the ring has been detected in scattered light so far, allowing a multi-wavelength analysis of the scattering properties of the dust grains present in this protoplanetary disk in combinati...

We investigate the structure and the stabilities of a protoplanetary disk, which is heated by viscous process in itself and by its central star. The disk is set to rotate with the Keplerian velocity and has the surface density distribution of the minimum mass solar nebula. We assume the vertical hydrostatic equilibrium and the radiative equilibrium at each point, and solve the two-dimensional r...