Numerical simulations show that the migration of growing planetary cores may be dominated by turbulent fluctuations in the protoplanetary disk, rather than by any mean property of the flow. We quantify the impact of this stochastic core migration on the formation time scale and core mass of giant planets at the onset of runaway gas accretion. For standard Solar Nebula conditions, the formation ...

We present a study of the structure and kinematics of the triple-shell planetary nebula NGC7662 based on long-slit echelle spectroscopic observations and HST archival narrow-band images. The structure of NGC 7662 main nebula consists of a central cavity surrounded by two concentric shells. The bright inner shell has a non-negligible thickness and the highest density in the nebula. The outer she...

The planetary nebula populations of relatively nearby galaxies can be easily observed and provide both a distance estimate and a tool with which dynamical information can be obtained. Usually the requisite radial velocities are obtained by multi-object spectroscopy once the planetary nebulae have been located by direct imaging. Here we report on a technique for measuring planetary nebula kinema...

We present deep narrowband near-IR images and moderate resolution spectra of the young planetary nebula Hubble 12. These data are the first to show clearly the complex structure for this important planetary nebula. Images were obtained at λ = 2.12, 2.16, and 2.26 μm. The λ = 2.12 μm image reveals the bipolar nature of the nebula, as well as complex structure near the central star in the equator...

We present deep narrowband near-IR images and moderate resolution spectra of the young planetary nebula Hubble 12. These data are the first to show clearly the complex structure for this important planetary nebula. Images were obtained at λ = 2.12, 2.16, and 2.26 μm. The λ = 2.12 μm image reveals the bipolar nature of the nebula, as well as complex structure near the central star in the equator...

We present [N ii] and Hα images and high resolution long–slit spectra of the planetary nebula IC4846, which reveal, for the first time, its complex structure and the existence of collimated outflows. The object consists of a moderately elongated shell, two (and probably three) pairs of collimated bipolar outflows at different orientations, and an attached circular shell. One of the collimated p...

Context. Until now, only one planetary nebula (PN) has been known in the Fornax dwarf spheroidal galaxy. Aims. The discovery of a second PN candidate, associated with one of the 5 globular clusters in the Fornax dwarf, is reported. Methods. Spectra of the globular cluster H5, obtained with the UVES echelle spectrograph on the ESO Very Large Telescope, show [O ] line emission at a radial velo...