Related papers: Gas infall via accretion disk feeding Cepheus A HW…
We present VLA and PdBI subarcsecond images (0.15"-0.6") of the radiocontinuum emission at 7 mm and of the SO2 J=19_{2,18}-18_{3,15} and J=27_{8,20}-28_{7,21} lines toward the Cepheus A HW2 region. The SO2 images reveal the presence of a…
The processes leading to the birth of low-mass stars such as our Sun have been well studied, but the formation of high-mass (> 8 x Sun's mass) stars has heretofore remained poorly understood. Recent observational studies suggest that…
Due to its relatively small distance (725 pc), the Cepheus A East star-forming region is an ideal laboratory to study massive star formation processes. Based on its morphology, it has been suggested that the flattened molecular gas…
We present near-infrared H2, radio CO, and thermal infrared observations of the nearby massive star-forming region Cepheus A (Cep A). From H2 bow shocks arranged along four distinct jet axes, we infer that the massive protostellar source…
Circumstellar disks are an essential ingredient of the formation of low-mass stars. It is unclear, however, whether the accretion-disk paradigm can also account for the formation of stars more massive than about 10 solar masses, in which…
We have measured the internal proper motions of the 6.7 GHz methanol masers associated with Cepheus A (Cep A) HW2 using Very Long Baseline Interferometery (VLBI) observations. We conducted three epochs of VLBI monitoring observations of the…
Young massive stars warm up the large amount of gas and dust which condenses in their vicinity, exciting a forest of lines from different molecular species. Their line brightness is a diagnostic tool of the gas physical conditions locally,…
Observations indicate that a continuous supply of gas is needed to maintain observed star formation rates in large, disky galaxies. To fuel star formation, gas must reach the inner regions of such galaxies. Despite its crucial importance…
We present polarization observations of the 6.7-GHz methanol masers around the massive protostar Cepheus A HW2 and its associated disc. The data were taken with the Multi-Element Radio Linked Interferometer Network. The maser polarization…
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…
Theory predicts and observations confirm that low-mass stars (like the Sun) in their early life grow by accreting gas from the surrounding material. But for stars ~ 10 times more massive than the Sun (~10 M_sun), the powerful stellar…
Aims: In order to test the nature of an (accretion) disk in the vicinity of Cepheus A HW2, we measured the three-dimensional velocity field of the CH3OH maser spots, which are projected within 1000au of the HW2 object, with an accuracy of…
It is well established that Solar-mass stars gain mass via disk accretion, until the mass reservoir of the disk is exhausted and dispersed, or condenses into planetesimals. Accretion disks are intimately coupled with mass ejection via polar…
A clear understanding of the chemical processing of matter, as it is transferred from a molecular cloud to a planetary system, depends heavily on knowledge of the physical conditions endured by gas and dust as these accrete onto a disk and…
We develop a model for the outer gravitationally unstable regions of accretion disks around massive black holes, for primeval or solar abundances. First we study star formation and evolution in a purely gaseous marginally unstable disk, and…
We show how the existence of a relation between the star formation rate and the gas density, i.e. the Kennicutt-Schmidt law, implies a continuous accretion of fresh gas from the environment into the discs of spiral galaxies. We present a…
Evidence for the accretion of cold gas in galaxies has been rapidly accumulating in the past years. HI observations of galaxies and their environment have brought to light new facts and phenomena which are evidence of ongoing or recent…
Evidence for a large scale flow of low density gas onto the Cepheus A young stellar cluster is presented. Observations of K-band near-infrared and multi-transition CS and N2H+ millimeter line emission are shown in relation to a…
Gas accretion, hot ($\sim 10^6\,{\rm K}$) atmospheres, and a tilt between the rotation axes of the disc and the atmosphere are all common predictions of standard galaxy evolution theory for massive star-forming galaxies at low redshift.…
Observations of the galactic center revealed a population of young massive stars within 0.4 pc from Sgr A* -- the presumed location of a supermassive black hole. The origin of these stars is a puzzle as their formation in citu should be…