Related papers: Massive extended streamers feed high-mass young st…
The disk components of galaxies generally show an exponential profile extending over several scale lengths, both in mass and star-formation rate, but the physical origin is not well understood. We explore a physical model in which the…
Gas giant planets are formed by gas accretion onto planetary cores in protoplanetary disks. However, direct evidence of this process is still lacking, limiting our understanding of planetary formation processes. During mass accretion,…
In addition to a supermassive black hole (SMBH), the central parsec of the Milky Way hosts over a hundred of massive, high velocity young stars whose existence, and organisation of a subset of them in one, or possibly two, mis-aligned…
We present multi-line and continuum observations of the circumstellar environment within 10^4 AU of a sample of protostars to investigate how the effects of outflows on their immediate environment changes over time. 12CO(1-0) emission…
Recent spectroscopic and VLBI-imaging observations of bright extragalactic water maser sources have revealed that the megamaser emission often originates in thin circumnuclear disks near the centers of active galactic nuclei (AGNs). Using…
Kant and Laplace suggested the Solar System formed from a rotating gaseous disk in the 18th century, but convincing evidence that young stars are indeed surrounded by such disks was not presented for another 200 years. As we move into the…
We have observed the submillimeter continuum condensations SMM2, SMM4, SMM9, and SMM11 in the star forming cluster Serpens Main using the Atacama Large Millimeter/submillimeter Array during Cycle 3 in the 1.3 mm continuum, 12CO J=2-1, SO…
Nearly all of the initial angular momentum of the matter that goes into each forming star must somehow be removed or redistributed during the formation process. The possible transport mechanisms and the possible fates of the excess angular…
We present simulations of the non-linear evolution of streaming instabilities in protoplanetary disks. The two components of the disk, gas treated with grid hydrodynamics and solids treated as superparticles, are mutually coupled by drag…
Stars in disks of spiral galaxies are usually assumed to remain roughly at their birth radii. This assumption is built into decades of modelling of the evolution of stellar populations in our own Galaxy and in external systems. We present…
Interpenetrating streams of solids and gas in a Keplerian disk produce a local, linear instability. The two components mutually interact via aerodynamic drag, which generates radial drift and triggers unstable modes. The secular instability…
Outflows of pre-main-sequence stars drive shocks into molecular material within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared, millimeter and submillimeter lines of many species including. Dust grains are important…
The streaming instability for solid particles in protoplanetary disks is re-examined assuming the familiar alpha ($\alpha$) model for isotropic turbulence. Turbulence always reduces the growth rates of the streaming instability relative to…
The study of the Milky Way stellar discs in the context of galaxy formation is discussed. In particular we explore the properties of the Milky Way disc using a new sample of about 550 dwarf stars for which we have recently obtained…
The formation of massive stars exceeding 10 solar masses usually results in large-scale molecular outflows. Numerical simulations, including ionization, of the formation of such stars show evidence for ionization-driven molecular outflows.…
Massive young stellar object (MYSOs) form during the collapse of high-mass pre-stellar cores, where infalling molecular material is accreted through a centrifugally-balanced accretion disc that is subject to efficient gravitational…
Debris disks are optically thin, almost gas-free dusty disks observed around a significant fraction of main-sequence stars older than about 10 Myr. Since the circumstellar dust is short-lived, the very existence of these disks is considered…
According to the magnetospheric accretion scenario, young low-mass stars are surrounded by circumstellar disks which they interact with through accretion of mass. The accretion builds up the star to its final mass and is also believed to…
A large fraction of bulgeless disk galaxies contain young compact stellar systems at their centers, in spite of the local gravitational stability of these disks. We evaluate two contrasting hypotheses for the origin of the nuclear star…
A detailed understanding of the physics of star and planet formation requires study of individual objects as well as statistical assessment of global properties and evolutionary trends. Observational investigations of circumstellar material…